Patent Application
20240224787
The present disclosure relates to an organic electroluminescent device, and more specifically to an organic electroluminescent device with low driving voltage, high luminous efficiency, and long lifespan characteristics as well as excellent blue phosphorescent emission.
In the structure of an organic electroluminescent device (hereinafter referred to as “organic EL device”), application of a voltage between two electrodes injects holes from the anode and electrons from the cathode into the organic layer. When the injected holes and electrons are combined with each other, excitons are generated and then return to a ground state, emitting light.
Electron spin types of the formed excitons classify organic EL devices into fluorescent EL devices in which singlet excitons contribute to light emission and phosphorescent EL devices in which triplet excitons are responsible for light emission.
Theoretically, depending on the generation ratio, the internal quantum efficiency amounts to at the most 25% for fluorescent EL devices and to up to 100% for phosphorescent EL devices. For phosphorescence, high internal quantum efficiency may be obtained because triplets and singlets are involved in internal quantum efficiency, but in the case of fluorescence, only singlet transition occurs, so the maximum internal quantum efficiency is about a quarter of that of phosphorescence. As such, the phosphorescent EL devices have theoretically higher luminous efficiency than the fluorescence.
For phosphorescent EL devices, the light-emitting layer includes a host material and a dopant material that produces emission through energy transfer from the host material. Among the dopant materials are Ir compounds based on the (4, 6-F2ppy) 2Irpic or fluorinated ppy ligand structures that have been developed for blue light emission, and CBP materials are widely used as host materials. However, CBP materials provides insufficient energy transfer to blue-emitting dopants, suffering from the disadvantages of low blue-emission efficiency and short lifetime for the devices.
The present disclosure aims to an organic EL device that not only exhibits low driving voltage, high luminous efficiency, and long lifespan characteristics, but also enables blue phosphorescent emission.
In accordance with an aspect thereof, the present disclosure provides an organic EL device including: an anode: a cathode; and at least one organic layer disposed between the anode and the cathode and including a light-emitting layer, wherein the light-emitting layer includes an iridium complex represented by the following Chemical Formula 1 and a compound represented by the following Chemical Formula 2:
(wherein,
Equipped with a light-emitting layer including specific structures of iridium complexes and hosts, the organic EL device of the present disclosure exhibits low driving voltage, high luminous efficiency, and long lifespan characteristics as well as enabling excellent blue phosphorescent emission.
Furthermore, application of the organic EL device of the present disclosure allows for the provision of display panels with enhanced performance and lifespan.
Advantages and features of the present disclosure and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the disclosure to those skilled in the art, and the present disclosure will only be defined by the appended claims. In some embodiments, process steps, device structures, and techniques well known in the art have not been described in detail in order to avoid obscuring the interpretation of the present disclosure. Like reference numerals will be used throughout to designate the same or like elements.
Otherwise defined, all terms used in the specification (including technical and scientific terms) may be used with meanings commonly understood by a person having ordinary knowledge in the art. Further, unless explicitly defined to the contrary, the terms defined in a generally-used dictionary are not ideally or excessively interpreted.
Below, each component of the organic EL device according to the present disclosure will be elucidated.
The organic EL device of the present disclosure includes the anode (100). The anode (100) may be disposed on a substrate and electrically connected to a driving thin film transistor to receive a driving current from the driving thin film transistor. Since the anode (100) includes or is formed of a material having a relatively high work function, it injects holes into an adjacent one of the organic layers, that is, the hole transport region (310) (e.g., a hole injection layer (311)).
So long as it is typically known in the art, any material may be used for the anode with no particular limitations imparted thereto. Examples thereof include metals, such as vanadium, chromium, copper, zinc, and gold; alloys thereof; metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al and SnO2:Sb; conductive polymers such as polythiophene, poly(3-methylthiophene), poly[3,4-(ethylene-1,2-dioxy)thiophene] (PEDT), polypyrrole, and polyaniline; carbon black, but are not limited thereto.
Any method that is known in the art may be employed for preparing the anode, with no limitations thereto. For example, the anode may be formed by coating the anode material on a substrate through a known thin film forming method such as a sputtering method, an ion plating method, a vacuum deposition method, or a spin coating method.
The substrate may be a plate-shaped member for supporting the organic EL device, and include, for example, a silicon wafer, quartz, a glass plate, a metal plate, a plastic film, and a sheet, but with no limitations thereto.
In the organic EL device of the present disclosure, the cathode (200) is disposed opposing the anode, and specifically, disposed on the electron transport region (330). Since the cathode (200) includes a material having a relatively low work function, it may inject electrons into an adjacent organic layer, that is, the electron transport region (330) (e.g., an electron injection layer (332)).
So long as it is typically known in the art, any cathode material may be used without particular limitations. Examples of the cathode material include metals, such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver (Ag), tin, and lead; alloys thereof; and a multi-layer structure material such as LiF/Al or LiO2/Al, but are not limited thereto.
No particular limitations are imparted to methods for preparing a cathode, and like the anode, the cathode may be prepared through a conventional method known in the art. By way of example, the cathode may be formed by coating the cathode material on at least one organic layer (300), specifically on the electron transport region, for example, the electron injection layer (332), through the above-described thin film forming method.
In the organic EL device of the present disclosure, at least one organic layer (300) is disposed between the anode (100) and the cathode (200) and includes a hole transport region (310), a light-emitting layer (320), and an electron transport region (330).
According to an embodiment, as shown in
Hereinafter, each organic layer will be described.
In the organic EL device (100) of the present disclosure, the hole transport region (310) is a portion of the organic layer (300) disposed on the anode (100), and serves to allow holes injected from the anode (100) to migrate into another adjacent one of the organic layers, specifically to the light-emitting layer (320).
The hole transport region (310) may include at least one selected from the group consisting of a hole injection layer (311) and a transport layer (312).
In an embodiment, as shown in
A material forming the hole injection layer (311) and the hole transport layer (312) in the present disclosure is not particularly limited as long as it has a low hole injection barrier and a high hole mobility, and any material for typically used the hole injection/transport layer in the art may be employed without limitation. In this regard, respective materials accounting for the hole injection layer (311) and the hole transport layer (312) may be same or different from each other.
Specifically, the hole injection layer (311) may include a hole injection material known in the art. Non-limiting examples of the hole injection material may phthalocyanine such include compounds as copper phthalocyanine; DNTPD (N,N′-diphenyl-N,N′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine), m-MTDATA (4,4′,4″-tris(3-methylphenylphenylamino) triphenylamine), TDATA (4,4′4″-Tris(N,N-diphenylamino)triphenylamine), 2TNATA (4,4′,4″-tris{N,-(2-naphthyl)-N-phenylamino}-triphenylamine), PEDOT/PSS (Poly(3,4-ethylenedioxythiophene)/Poly(4-styrenesulfonate)), PANI/DBSA (Polyaniline/Dodecylbenzenesulfonic acid), PANI/CSA (Polyaniline/Camphor sulfonic acid), PANI/PSS ((Polyaniline)/Poly(4-styrenesulfonate)), and the like, which may be used solely or in combination of two or more thereof.
The hole transport layer (312) includes a hole transport material known in the art. Non-limiting examples of the hole transport material may include carbazole-based derivatives such as N-phenylcarbazole and polyvinylcarbazole; fluorene-based derivatives; amine-based derivatives; triphenylamine-based derivatives such as TPD (N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine) and TCTA (4,4′,4″-tris(N-carbazolyl)triphenylamine); NPB (N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine), TAPC (4,4′-cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine]), and the like, which may be used solely or in combination of two or more thereof.
The hole transport region (310) may be formed through a conventional method known in the art. For example, a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, a laser induced thermal imaging (LITI) method, and the like may be available, but with no limitations thereto.
In the organic EL device of the present disclosure, the light-emitting layer (320) is a portion of the organic layer (300) disposed between the anode (100) and the cathode (200), and specifically disposed on the hole transport region 320. Specifically, the light-emitting layer (320) may be disposed on the hole transport layer (312) (see
The light-emitting layer according to the present disclosure includes an iridium complex represented by Chemical Formula 1 and a compound represented by Chemical Formula 2. Thus, the organic EL device of the present disclosure not only possesses characteristics of low driving voltage, high efficiency, and long lifespan, but it can also exhibit excellent blue light emission characteristics. According to an embodiment, the organic EL device of the present disclosure can produce blue light emission with CIE coordinates where the x-value is 0.15-0.25 and the y-value is 0.08-0.20.
The iridium complex represented by Chemical Formula 1 is used as a dopant, specifically as a blue phosphorescent dopant.
In the iridium complex represented by Chemical Formula 1, R1 may be an alkyl of C1-C20 and specifically an alkyl of C1-C10. According to an embodiment, R1 may be selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or sec-butyl, and tert-butyl.
In Chemical Formula 1 that accounts for the iridium complex, a is an integer of 0 to 2 and specifically 0 or 1. The case where a is 0 indicates that any of the hydrogens is not substituted by the substituent R2. When a is 1 or 2, the hydrogen (s) is (are) substituted by the substituent R2. Given, the multiple R2's may be same or different and are each independently selected from the group consisting of a deuterium atom, a halogen, a cyano, an alkyl of C1-C20, an alkenyl of C2-C40, an alkynyl of C2-C20, a cycloalkyl of C3-C20, a heterocycloalkyl of 3 to 20 nuclear atoms, an aryl of C6-C20, a heteroaryl of 5 to 20 nuclear atoms, an alkyloxy of C1-C20, and an aryloxy of C6-C20, and specifically from the group consisting of a deuterium atom, a halogen, a cyano, an alkyl of C1-C20, an aryl of C6-C20, and a heteroaryl of 5 to 20 nuclear atoms.
In Chemical Formula 1 accounting for the iridium complex, b is an integer of 0 to 3 and specifically 0 or 1. The case where b is 0 mean that none of the hydrogens are substituted by the substituent R3. When b is an integer of 1 to 3, the hydrogen (s) is (are) substituted by the substituent R3. Given, the multiple R3's may be same or different and are each independently selected from the group consisting of a deuterium hydrogen, a halogen, a cyano, an alkyl of C1-C20, an alkenyl of C2-C40, an alkynyl of C2-C20, a cycloalkyl of C3-C20, a heterocycloalkyl of 3 to 20 nuclear atoms, an aryl of C6-C20, a heteroaryl of 5 to 20 nuclear atoms, an alkyloxy of C1-C20, and an aryloxy of C6-C20 and specifically from the group consisting of a deuterium atom, a halogen, a cyano, an alkyl of C1-C20, an aryl of C6-C20, and a heteroaryl of 5 to 20 nuclear atoms.
In Chemical Formula 1 accounting for the iridium complex, R4 and R5 may be same or different and are each independently a hydrogen atom or an alkyl of C1-C20 and specifically an alkyl of C1-C10. However, at least one of R4 and R5 may be an alkyl of C1-C20 and specifically an alkyl of C1-C10. Examples of the alkyl include, but are not limited to, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, and sec-butyl, tert-butyl.
The iridium complex represented by Chemical Formula 1 may be an iridium complex represented by the following Chemical Formula 1a, but is not limited thereto.
wherein,
In the iridium complex represented by Chemical Formula 1, the
moiety is bonded to the benzene ring of the parent ligand
moiety at an angle of 0 to 90° with regard to the plane of the parent ligand moiety. According to an embodiment, the
moiety is orthogonal to the plane of the
moiety and is bonded to the benzene ring. With such a structure, the iridium complex of Chemical Formula 1 increases in the energy of the ligand skeleton, which is the luminescent source. In addition, the addition of a radial structure centered on the iridium metal can achieve deep blue luminescence and enhance the lifespan of the device. Furthermore, the iridium complex of Chemical Formula 1 can achieve deep blue luminescence even in low-temperature or solid-state luminescence.
The iridium complex represented by Chemical Formula 1 may be an iridium complex represented by the following Chemical Formula 1b or 1c, but with no limitations thereto.
wherein, Me stands for methyl.
In the light-emitting layer, the compound represented by Chemical Formula 2 is used as a host and specifically as a blue phosphorescent host and is responsible, together with the iridium complex of Chemical Formula 1, for deep-blue phosphorescent emission.
In the compound represented by Chemical Formula 2, c and d are each an integer of 0 to 8 and specifically 0 or 1, and e and f are each an integer of 0 to 4 and specifically 0 or 1. The case where c, d, e, and f are each 0 means that any of the hydrogens is not substituted by the substituent (R6, R7, R8, and R9). When c and d are each an integer of 1 to 8 and e and f are each an integer of 1 to 3, any of the hydrogens is substituted by the substituents (R6, R7, R8, R9). In this regard, the multiple R6's, the multiple R7's, the multiple R8's, and the multiple R9's may be same or different and are each selected from the group consisting of a deuterium atom, a halogen, a cyano, an alkyl of C1-C20, an alkenyl of C2-C40, an alkynyl of C2-C20, a cycloalkyl of C3-C20, a heterocycloalkyl of 3 to 20 nuclear atoms, an aryl of C6-C20, a heteroaryl of 5 to 20 nuclear atoms, an alkyloxy of C1-C20, and an aryloxy of C6-C20 and specifically from the group consisting of a deuterium atom, a halogen, a cyano, an alkyl of C1-C20, an aryl of C6-C20, and a heteroaryl of 5 to 20 nuclear atoms.
The compound represent by Chemical Formula 2 may be a compound represented by the following Chemical Formula 2a, but with no limitations thereto.
wherein, c, d, R6, and R7 are each defined as in Chemical Formula 2.
The iridium complex represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 may be used (mixed) at a weight ratio of 1:99-30:70.
The light-emitting layer (320) may be a single layer or a multilayer structure composed of two or more layers. In this regard, when the light-emitting layer (320) includes a plurality of layers, the organic EL device may emit light of various colors. Specifically, the present disclosure may provide an organic EL device in which a plurality of light-emitting layers including heterogeneous materials are arranged in series to express a mixed color. In addition, when employed, a plurality of light-emitting layers requires an increased driving voltage in the device, but makes the current value constant in the organic EL device, thus enabling the provision of an organic EL device with improved luminous efficiency by the number of light-emitting layers.
The light-emitting layer (320) may be constructed through a conventional method known in the art. For example, a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, a laser induced thermal imaging (LITI) method, and the like are available, but with no limitations thereto. In an embodiment, the light-emitting layer may be formed by co-depositing the iridium complex of chemical formula 1 and the compound (host) of chemical formula 2.
In the organic EL device according to the present disclosure, the electron transport region (330) is an organic layer disposed on the light-emitting layer (320), functioning to move electrons injected from the cathode (200) to the light-emitting layer (320).
The electron transport region (330) may include at least one selected from the group consisting of the electron transport layer (331) and the electron injection layer (332).
In an embodiment, as shown in
In the electron transport region (330) according to the present disclosure, any electron transport material that facilitates electron injection and has high electron mobility may be used for the electron transport layer (331) without limitations. Non-limiting examples of the electron transport material include oxazole-based compounds, isoxazole-based compounds, triazole-based compounds, isothiazole-based compounds, oxadiazole-based compounds, thiadiazole-based compounds, perylene-based compounds, aluminum complexes [e.g., Alq3 (tris(8-quinolinolato)-aluminum), BAlq, SAlq, Alph3, Almq3], and gallium complexes (e.g., Gaq′2OPiv, Gaq′2OAc, 2(Gaq′2)), which may be used solely or in combination thereof.
In addition, any electron injection material that facilitates electron injection and has high electron mobility may be used for the electron injection layer (332) without limitations. Non-limiting examples of the electron injection material may include LiF, Li2O, Bao, NaCl, and CsF; lanthanide metals such as Yb; a metal halide such as RbCl or RbI, and the like, which may be used solely or in combination thereof.
The electron transport region (330) according to the present disclosure, specifically, the electron transport layer (331) and/or the electron injection layer (332) may be co-deposited with an n-type dopant to facilitate injection of electrons from the cathode. In this regard, any alkali metal complex compound known in the art may be used as the n-type dopant, without limitations, and examples thereof include alkali metals, alkaline earth metals, and rare earth metals.
The electron transport region (330) may be formed through a conventional method known in the art. For example, a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, and a laser induced thermal imaging (LITI) method are available, but with no limitations thereto.
The organic EL device 100 of the present disclosure may further include a light-emitting auxiliary layer, although not shown, disposed between the hole transport region (310) and the light-emitting layer (320).
The light-emitting auxiliary layer serves to control a thickness of the organic layer 300, while transporting holes from the hole transport region (310) to the light-emitting layer (320) or blocking the migration of electrons and/or excitons. In particular, the light-emitting auxiliary layer has a high LUMO value to prevent electrons from migrating to the hole transport layer (312) and has a high triplet energy to prevent excitons of the light-emitting layer (320) from being diffused to the hole transport layer (312).
The light-emitting auxiliary layer may include a hole transport material and may include or be formed of a material the same as a material of the hole transport region. In addition, the light-emitting auxiliary layers of the red, green, and blue organic EL devices may include or be formed of the same material.
No particular limitations are imparted to materials for the light-emitting auxiliary layer, and examples thereof include carbazole derivatives and arylamine derivatives. Specifically, examples of the light-emitting auxiliary layer may include NPD (N,N-dinaphthyl-N,N′-diphenyl benzidine), TPD (N,N′-bis-(3-methylphenyl)-N,N′-bis(phenyl)-benzidine), s-TAD, MTDATA (4,4′,4″-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine), and the like, but with no limitations thereto. These may be used solely or in combination.
The light-emitting auxiliary layer may further include a p-type dopant in addition to the above-described material. Any p-type dopant may be used in the present disclosure without particular limitations if it is typically known in in the art. In this regard, a content of the p-type dopant may be appropriately adjusted within a range known in the art, for example, in a range of about 0.5 to 50 parts by weight, based on 100 parts by weight of the hole transport material (100).
The light-emitting auxiliary layer may be formed by a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, a laser induced thermal imaging (LITI) method, and the like known in the art, but with no limitations thereto.
The organic EL device (100) of the present disclosure may further include a hole blocking layer (not shown) between the light-emitting layer (320) and the electron transport region (330).
The hole blocking layer (333) functions to block the diffusion of excitons or holes generated in the light-emitting layer (320) into the electron transport layer (331), thus allowing for the improvement of lifespan in the organic EL device.
So long as it is typically known in the art, any material possessing electron transport properties may be used for the hole blocking layer, without any limitation. Examples of the hole blocking layer material include 2,9-dimethyl-4,7-diphenyl-1,10-phenantroline (BCP) and bis(2-methyl-8-quinolinolato) (4-phenyl-phenolato) aluminum (III) (BAlq).
The hole blocking layer can be formed by a vacuum deposition method, a spin coating method, a casting method, a Langmuir-Blodgett (LB) method, an inkjet printing method, a laser printing method, or a laser induced thermal imaging (LITI) method, but with no limitations.
Optionally, the organic EL device (100) of the present disclosure may further include a capping layer (not shown) disposed on the cathode (200).
The capping layer may serve to allow light generated in the organic layer to be efficiently emitted to the outside while protecting the organic EL device.
The capping layer may include at least one of tris-8-hydroxyquinoline aluminum (Alq3), ZnSe, 2,5-bis(6′-(2′,2″-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole, 4′-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl (α-NPD), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD), and 1,1′-bis(di-4-tolylaminophenyl) cyclohexane (TAPC). The material for forming such a capping layer is inexpensive as compared to materials of other layers of the organic EL device.
The capping layer may be a single layer, but may include two or more layers having different refractive indices so that the light undergoes a change in refractive index gradually changes while passing through the two or more layers.
The capping layer may be prepared by a conventional method known in the art, and for example, various methods such as a vacuum deposition method, a spin coating method, a casting method, or a Langmuir-Blodgett (LB) method may be used.
As such, the organic EL device according to the present disclosure has a structure in which the anode (100), the organic layer (300) and the cathode (200) are sequentially stacked. In some cases, an insulating layer (not shown) or an adhesive layer (not shown) may be further included between the anode (100) and the organic layer (300) or between the cathode (200) and the organic layer (300). The organic EL device of the present disclosure may have excellent lifespan characteristics because a half-life time of initial brightness is increased while maintaining maximum luminous efficiency when voltage and current are applied.
The organic EL device of the present disclosure described above may be prepared according to a conventional method known in the art. For example, after vacuum deposition of an anode material on a substrate, a hole transport region material, a light-emitting layer material, an electron transport region material, and a cathode material may be vacuum-deposited on the anode, and thus an organic EL device may be manufactured.
A better understanding of the present disclosure may be obtained through the following examples which are set forth to illustrate, but are not to be construed to limit, the present disclosure.
All synthesis reactions were carried out in dry N2 atmospheres. All solvents s were distilled in sodium-benzophenone under nitrogen before use. Glass wares, syringes, magnetic stirrers, and needles were dried for 4 hours in a convection oven. The reactions were monitored using thin layer chromatography (TLC; Merck Co.). The spots developed on the TLC were identified under UV light at wavelengths of 254 or 365 nm. Column chromatography was performed on Silica gel 60 G (particle size: 5-40 μm; Merck Co.). The synthesized compounds were characterized using 1H-NMR, 13C-NMR spectrometer, elemental analyzer, and high-resolution mass spectrometry (HR-MS). The 1H-NMR spectrum was recorded on a Varian Mercury 300 (operating at 300.1 MHz), and the 13C-NMR spectrum was recorded at KBSI Ochang Center using Bruker Avance II 400 or Avance III HD 700 MHz spectrometers (operating at 100 or 176.1 MHz). HR-MS analysis and elemental analysis were conducted using LC/MS/MSn (n=10) spectrometry (Thermo Fisher Scientific, LCQ Fleet Hyperbolic Ion Trap MS/MSn Spectrometer) and Thermo Scientific FLASH EA-2000 Organic Elemental Analyzer, respectively. The melting points (mp) were recorded on a BuChi B540 apparatus (BuChi Labortechnik AG, Flawil, Switzerland) and were uncorrected. Absorption and emission spectra at room temperature (RT) were recorded using UV-Vis spectrophotometry (Agilent, Cary-5000) and fluorimetry (Varian, Cary Eclipse), respectively. Iridium (III) chloride hydrate was purchased from Sigma-Aldrich and was used without further purification. The fac-/mer-Ir(C{circumflex over ( )}CH)3 was synthesized according to previously reported methods
The methylated phenylimidazole ligand (L1) HC{circumflex over ( )}CMe was obtained through the Ullmann cross-coupling reaction between 1H-imidazole and 1-bromo-2-methylbenzene, followed by methylation with CH3I. In this regard, HC{circumflex over ( )}CMe was refluxed for 12 hours, filtered, and washed with a chilled organic solvent to synthesize the ligand ([HC{circumflex over ( )}CMe]+) as a white salt. Details are given as follows.
A solution of 1H-imidazole (7.96 g, 117 mmol), 1-bromo-2-methylbenzene (5.00 g, 29.2 mmol), CuI (1.11 g, 20 mol %), and K2CO3 (8.08 g, 58.5 mmol) in DMF (100 mL) was refluxed at 180° C. for 72 hours under a N2 atmosphere. The reaction mixture was quenched with H2O, and the product was extracted with CH2Cl2 (3×150 mL) and dried over MgSO4, and then the solvent was evaporated under reduced pressure. The crude product was used in the next reaction without further purification. A mixture of HC{circumflex over ( )}CMe (5.00 g) and CH3I (20.0 g) in THE solvent (100 mL) was refluxed for 12 hours under a N2 atmosphere. After cooling to room temperature, THF (100 mL) was added, resulting in a white precipitate. The white precipitate was filtered off and washed with cold THE and n-hexane. The resulting white solid was dried in a vacuum oven for 6 hours, and the pure product was obtained in quantitative yield. [mp 139.6-141.2° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH 9.45 (s, 1H), 8.05 (s, 1H), 7.96 (s, 1H), (7.55-7.46) (m, 4H), 3.96 (s, 3H), 2.23 (s, 3H); 13C-NMR (100.6 MHZ, CDCl3) δ 136.65, 133.32, 133.00, 131.78, 130.87, 127.47, 126.09, 124.35, 123.01, 37.48, 17.92; ESI-MS (m/z): calcd. for C11H13N2+: 173.1073, Found [M−I]+: 173.1212; Elemental analysis result (%): C 44.13, H 4.37, N 9.30 (Calcd (%): C 44.02, H 4.37, N 9.33)]
The mono-brominated 1-(2-bromophenyl)-1H-imidazole precursor was obtained through the Ullmann cross-coupling reaction between 1H-imidazole and 1,2-dibromobenzene, followed by Suzuki-Miyaura coupling reaction between the 1-(2-bromophenyl)-1H-imidazole and phenylboronic acid to derive an arylated phenylimidazole ligand (L2), HC{circumflex over ( )}CPh. Subsequently, methylation of HC{circumflex over ( )}CPh with CH3I was performed by refluxing for 12 hours, filtering at room temperature, and washing with cold organic solvent to afford the ligand ([HC{circumflex over ( )}CPh]+) as a white salt. Details are given as follows.
A solution of 1-(2-bromophenyl)-1H-imidazole (5.00 g, 22.4 mmol), phenylboronic acid (3.01 g, 24.7 mmol), Pd2(dba)3 (1.03 g, 5 mol %), SPhos (0.92 g, 2.24 mmol), and K2CO3 (15.5 g, 112.1 mmol) in CH3CN/H2O (3:1, v/v) (100 mL) was refluxed at 110° Cl for 16 hours under a N2 atmosphere. The reaction mixture was quenched with H2O, and the product was extracted with CH2Cl2 (3×150 mL) and dried over MgSO4, and then the solvent was evaporated at a reduced pressure. The crude product was used in the next reaction without further purification. A mixture of HC{circumflex over ( )}CPh (5.60 g) and CH3I (16.0 g) in THE solvent (100 mL) was refluxed for 12 hours under a N2 atmosphere. After cooling to room temperature, THF (100 mL) was added, resulting in a white precipitate. The white precipitate was filtered off and washed with cold THE and n-hexane. The resulting white solid was dried in a vacuum oven for 6 hours, and the pure product was obtained in quantitative yield. [mp 177.6-178.1° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH 9.35 (s, 1H), (7.74-7.37) (m, 6H), 7.38 (d, J=1.8 Hz, 3H), (7.23-7.20) (m, 2H), 3.85 (s, 3H); 13C-NMR (100.6 MHz, CDCl3) δC 137.27, 137.24, 135.98, 132.09, 131.75, 131.15, 129.61, 129.23, 128.60, 128.48, 126.52, 123.48, 123.21, 37. 70; ESI-MS (m/z): calcd. for C16H15N2+: 235.1230, Found [M−I]+: 235.1233; Elemental analysis result (%): C 53.15, H 4.16, N 7.73 (Calcd (%): C 53.06, H 4.17, N 7.73).
The target ligand was synthesized in the same manner as in Preparation Example 2 (for synthesis of [HC{circumflex over ( )}CPh]+), with the exception of using o-tolylboronic acid (3.35 g, 24.7 mmol) instead of phenylboronic acid (3.01 g, 24.7 mmol) [mp 173.2-174.7° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH 9.33 (s, 1H), (7.77-7.69) (m, 4H), (7.56-7.51) (m, 2H), (7.26-7.11) (m, 4H), 3.82 (s, 3H), 2.02 (s, 3H); 13C-NMR (100.6 MHz, CDCl3) δC 136.98, 136.52, 135.62, 135.35, 132.64, 131.91, 130.80, 130.69, 129.77, 129.44, 128.98, 126.50, 126.00, 123.40, 122.66, 37.59, 20.00; ESI-MS (m/z): calcd. for C17H17N2+ 249.1386, Found [M−I]+: 249.1389; Elemental analysis result (%): C 53.97, H 4.57, N 7.46 (Calcd (%): C 54.27, H 4.55, N 7.45)].
The target ligand was synthesized in the same manner as in Preparation Example 2 (for synthesis of [HC{circumflex over ( )}CPh]+), with the exception of using 2,6-dimethylphenylboronic acid (3.70 g, 24.7 mmol) instead of phenylboronic acid (3.01 g, 24.7 mmol) [mp 191.0-192.5° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH 9.23 (s, 1H), (7.78-7.71) (m, 3H), 7.68 (s, 1H), 7.44 (d, J=7.5 Hz, 1H), 7.40 (s, 1H), 7.19 (t, J=7.8 Hz, 1H), 7.10 (d, J=7.5 Hz, 2H), 3.81 (s, 3H), 1.92 (s, 6H); 13C-NMR (100.6 MHz, CDCl3) δC 136.88, 135.96, 135.17, 135.05, 132.62, 131.81, 131.14, 129.97, 128.88, 128.13, 126.08, 123.41, 122.15, 37.67, 20.72; ESI-MS (m/z): calcd. for C18H19N2+: 263.1543, Found [M−I]+: 263.1546; Elemental analysis result (%): C 55.43, H 4.92, N 7.75 (Calcd (%): C 55.40, H 4.91, N 7.78)].
A solution of [HC{circumflex over ( )}CMe]+ (3.00 g, 10 mmol) synthesized in Preparation Example 1, Ag2CO3 (1.38 g, 5.00 mmol), Na2CO3 (0.53 g, 5.00 mmol), and IrCl3·xH2O (0.88 g, 2.50 mmol) in 2-ethoxyethanol (100 mL) was reflexed for 72 hours in N2 atmosphere. After being cooled to room temperature, the reaction mixture was added to water. The precipitate thus formed was collected by filtration and washed with H2O and n-hexane. Gray crude powder was coated with silica and purified by column chromatography using CH2Cl2/ethyl acetate/n-hexane (1:1:4, v/v) as a eluent, to afford the title compounds as off-white solids [fac-Ir(C{circumflex over ( )}CMe)3 (Rf=0.4) and mer-Ir(C{circumflex over ( )}CMe)3 (Rf=0.6)].
{circle around (1)} fac-Ir(C{circumflex over ( )}CMe)3. (0.85 g, yield 12%); mp not detected; 1H-NMR (300.1 MHZ, DMSO-d6): δH 7.85 (s, 3H), 7.13 (s, 3H), (6.53-6.50) (m, 3H), (6.35-6.30) (m, 6H), 2.95 (s, 9H), 2.54 (s, 9H); 13C-NMR (176.1 MHZ, DMSO-d6) δC 177.11, 152.54, 146.29, 135.21, 124.13, 123.42, 120.58, 119.73, 117.60, 35.93, 21.72; ESI-MS (m/z): calcd. for C33H33IrN6: 706.2396, Found [M]+: 706.2439; Elemental analysis result (%): C 56.01, H 4.69, N 11.55 (Calcd (%): C 56.15, H 4.71, N 11.91).
{circle around (2)} mer-Ir(C{circumflex over ( )}CMe)3. (2.18 g, yield 31%); mp 391.1-392.7° C.; 1H-NMR (300.1 MHZ, CD2Cl2-d2): δH 7.87 (d, 1H), 7.81 (d, J=1.8 Hz 1H), 7.75 (d, J=2.4 Hz 1H), 6.79 (d, J=2.7 Hz, 1H), 6.77 (d, J=2.4 Hz, 1H), 6.69 (d, J=1.5 Hz, 1H), (6.63-6.46) (m, 9H), 3.03 (s, 3H), 3.00 (s, 3H), 2.94 (s, 3H), 2.61 (s, 3H), 2.59 (s, 6H); 13C-NMR (176.1 MHz, DMSO-d6) δC 177.15, 175.36, 174.53, 154.18, 153.15, 152.26, 147.23, 146.69, 145.92, 137.94, 137.55, 135.31, 124.54, 124.30, 124.15, 124.03, 123.97, 123.94, 120.65, 120.59, 119.94, 119.88, 119.70, 119.35, 118.10, 118.00, 117.95, 37.42, 37.14, 36.10, 22.29, 22.01, 21.91; ESI-MS (m/z): calcd. for C33H33IrN6: 706.2396, Found [M]+: 706.2416; Elemental analysis result (%): C 56.14, H 4.74, N 11.92 (Calcd (%): C 56.15, H 4.71, N 11.91).
The target compounds fac-Ir(C{circumflex over ( )}CPh)3 and mer-Ir(C{circumflex over ( )}CPh)3 were synthesized in the same manner as in Comparative Synthesis Example 1, with the exception of using 2-ethoxyethanol (80 mL), [HC{circumflex over ( )}CPh]+ synthesized in Preparation Example 2 (3.00 g, 8.28 mmol), Ag2CO3 (1.14 g, 4.14 mmol), Na2CO3 (0.44 g, 4.14 mmol), and IrCl3·xH2O (0.73 g, 2.07 mmol). Purification silica through gel column chromatography using CH2Cl2/ethyl acetate/n-hexane (1:1:4, v/v) as an eluent afforded the compounds as off-white solids [fac-Ir(C{circumflex over ( )}CPh)3 (Rf=0.2) and mer-Ir(C{circumflex over ( )}CPh)3 (Rf=0.5)].
{circle around (1)} fac-Ir(C{circumflex over ( )}CPh)3. (0.81 g, yield 11%); mp 377.3-378.8° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH (7.50-7.40) (m, 9H), 7.31 (d, J=6.6 Hz, 6H), 6.86 (s, 3H), (6.65-6.58) (m, 9H), 6.03 (s, 3H), 2.94 (s, 9H); 13C-NMR (100.6 MHZ, CDCl3) δC 177.92, 152.50, 144.61, 142.37, 136.91, 130.16, 129.21, 128.33, 128.29, 127.12, 126.84, 123.87, 123.48, 118.52, 118.43, 36.44; ESI-MS (m/z): calcd. for C48H39IrN6: 892.2865, Found [M]+: 892.2868; Elemental analysis result (%): C 64.70, H 4.44, N 9.39 (Calcd (%): C 64.63, H 4.41, N 9.42).
{circle around (2)} mer-Ir (C{circumflex over ( )}CPh)3. (2.07 g, yield 28%); mp 329.1-330.6° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH (7.52-7.40) (m, 9H), (7.36-7.29) (m, 4H), (7.23-7.21) (m, 2H), 6.91 (d, J=2.7 Hz, 1H), 6.87 (d, J=1.8 Hz, 1H), (6.82-6.79) (m, 2H), (6.62-6.51) (m, 7H), (6.43-6.39) (m, 1H), 6.11 (d, J=1.8 Hz, 1H), 6.08 (d, J=2.7 Hz, 1H), 6.02 (d, J=2.7 Hz, 1H), 3.01 (s, 3H), 2.98 (s, 3H), 2.96 (s, 3H); 13C-NMR (176.1 MHZ, DMSO-d6) δC 176.68, 173.74, 173.48, 154.62, 152.39, 150.82, 144.96, 144.39, 143.68, 141.74, 141.59, 141.53, 137.95, 137.68, 136.00, 129.36, 129.29, 129.15, 129.02, 128.90, 128.85, 128.80, 128.75, 128.63, 128.44, 128.42, 127.28, 127.25, 127.01, 126.91, 126.71, 123.89, 123.48, 123.04, 122.53, 122.44, 120.68, 120.52, 120.22, 117.46, 117.40, 117.02, 36.66, 36.39, 35.36; ESI-MS (m/z): calcd. for C48H39IrN6: 892.2865, Found [M]+: 892.2612; Elemental analysis result (%): C 64.34, H 4.39, N 9.44 (Calcd (%): C 64.63, H 4.41, N 9.42).
The target compounds fac-Ir(C{circumflex over ( )}CH)3 and mer-Ir(C{circumflex over ( )}CH)3 were synthesized as described previously (Sajoto, T.; Djurovich, P. I.; Tamayo, A.; Yousufuddin, M.; Bau, R.; Thompson, M. E.; Holmes, R. J.; Forrest, S. R. Blue and near-UV phosphorescence from iridium complexes with cyclometalated pyrazolyl or N-heterocyclic carbene ligands. Inorg. Chem. 2005, 44, 7992-8003.).
The target compounds fac-Ir(C{circumflex over ( )}CMePh)3 and mer-Ir(C{circumflex over ( )}CMePh)3 were synthesized in the same manner as in Comparative Synthesis Example 1, with the exception of using 2-ethoxyethanol (70 mL), [HC{circumflex over ( )}CMePh]+ synthesized in Preparation Example 3 (2.50 g, 6.64 mmol), Ag2CO3 (0.92 g, 3.32 mmol), Na2CO3 (0.35 g, 3.32 mmol), and IrCl3·xH2O (0.59 g, 1.66 mmol). Purification through silica gel column chromatography using CH2Cl2/ethyl acetate/n-hexane (1:1:4, v/v) as an eluent afforded the target compounds as off-white solids [fac-Ir(C{circumflex over ( )}CMePh)3 (Rf=0.4) and mer-Ir(C{circumflex over ( )}CMePh)3 (Rf=0.7)].
{circle around (1)} fac-Ir(C{circumflex over ( )}CMePh)3. (0.50 g, yield 8%); mp 379.9-380.4° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH (7.33-7.18) (m, 12H), 6.84 (s, 3H), (6. 63-6.50) (m, 9H), (5.87-5.85) (m, 3H), (2.95-2.84) (m, 9H), (1.97-1.95) (m, 9H); 13C-NMR (176.1 MHz, CDCl3) δC 177.80, 153.01, 145.03, 141.80, 136.86, 136.37, 130.19, 129.63, 128.15, 126.70, 126.02, 123.88, 122.57, 120.80, 116.36, 36.26, 20.02; ESI-MS (m/z): calcd. for C51H45IrN6: 934.3335, Found [M]+: 934.3323; Elemental analysis result (%): C 65.55, H 4.83, N 8.95 (Calcd (%): C 65.57, H 4.86, N 9.00).
{circle around (2)} mer-Ir(C{circumflex over ( )}CMePh)3. (1.49 g, yield 24%); mp 232.9-233.5° C.; 1H-NMR (300.1 MHZ, DMSO-d6): δH (7.33-7.11) (m, 12H), (6.89-6.82) (m, 3H), (6.60-6.43) (m, 9H), (5.96-5.87) (m, 3H), (3.02-2.85) (m, 9H), (1.98-1.91) (m, 9H); 13C-NMR (176.12 MHZ, DMSO-d6) δC 176.64, 173.81, 173.57, 154.45, 152.38, 150.45, 144.87, 144.30, 143.69, 141.28, 141.15, 141.13, 138.19, 137.70, 135.91, 129.84, 129.74, 129.67, 129.58, 129.48, 129.45, 129.40, 129.35, 129.29, 129.23, 129.08, 127.71, 126.36, 126.27, 126.22, 126.13, 125.95, 125.71, 125.55, 124.38, 124.22, 123.75, 123.09, 122.99, 120.96, 120.87, 120.55, 116.29, 116.20, 115.97 36.65, 36.57, 35.19, 19.91 , 19.58 , 19.53; ESI-MS (m/z): calcd. for C51H45IrN6: 934.3335, Found [M]+: 934.3413); Elemental analysis result (%): C 65.52, H 4.85, N 8.96 (Calcd (%): C 65.57, H 4.86, N 9.00).
The target compounds fac-Ir(C{circumflex over ( )}CdiMePh)3 and mer-Ir(C{circumflex over ( )}CdiMePh)3 were synthesized in the same manner as in Comparative Synthesis Example 1, with the exception of using 2-ethoxyethanol (70 mL), [HC{circumflex over ( )}CdiMePh]+ synthesized in Preparation Example 4 (2.80 g, 7.17 mmol), Ag2CO3 (0.99 g, 3.59 mmol), Na2CO3 (0.38 g, 3.59 mmol), and IrCl3·xH2O (0.63 g, 1.79 mmol). Purification through silica gel column chromatography using CH2Cl2/ethyl acetate/n-hexane (1:1:3, v/v) as an eluent afforded the target compounds as off-white solids [fac-Ir(C{circumflex over ( )}CdiMePh)3 (Rf=0.4) and mer-Ir(C{circumflex over ( )}CdiMePh)3 (Rf=0.6)].
{circle around (1)} fac-Ir(C{circumflex over ( )}CdiMePh)3. (0.63 g, yield 9%); mp 382.2-383.7° C.; 1H-NMR (300.1 MHz, DMSO-d6): δH (7.27-7.17) (m, 9H), 6.81 (s, 3H), 6.64 (d, J=7.2 Hz, 3H), 6.55 (t, J=7.2 Hz, 3H), 6.42 (d, J=7.2 Hz, 3H), 5.79 (s, 3H), 2.89 (s, 9H), 1.98 (s, 9H), 1.91 (s, 9H); 13C-NMR (100.6 MHZ, CDCl3) δ 178.90, 152.13, 144.29, 141.39, 137.66, 136.50, 136.24, 128.06, 127.50, 126.99, 124.60, 121.88, 119.50, 118.91, 116.84, 36.34, 20.59; ESI-MS (m/z): calcd. for C54H51IrN6: 976.3804, Found [M]+: 976.3821; Elemental analysis result (%): C 66.80, H 5.27, N 8.54 (Calcd (%): C 66.44, H 5.27, N 8.61).
{circle around (2)} mer-Ir(C{circumflex over ( )}CdiMePh)3. (1.47 g, yield 21%); mp 299.6-301.2° C.; 1H-NMR (300.1 MHz, DMSO-d6): δH (7.24-7.17) (m, 9H), 6.91 (d, J=7.5 Hz, 1H), (6.83-6.80) (m, 3H), 6.63 (t, J=6.9 Hz, 1H), (6.58-6.50) (m, 3H), 6.36 (d, J=7.2 Hz, 3H), 6.30 (d, J=7.2 Hz, 1H), (5.89-5.88) (m, 2H), 5.79 (s, 1H), 3.05 (s, 3H), 2.95 (s, 3H), 2.88 (s, 3H), 1.99 (s, 3H), 1.93 (s, 3H), 1.91 (s, 3H) 1.85 (s, 3H), 1.83 (s, 3H), 1.78 (s, 3H); 13C-NMR (100.6 MHz, CDCl3) δC 178.90, 177.36, 175.92, 174.63, 154.89, 152.14, 144.90, 144.28, 141.38, 139.12, 138.38, 137.74, 137.66, 137.51, 137.05, 136.80, 136.65, 136.50, 136.22, 136.13, 135.76, 127.51, 127.45, 127.34, 127.18, 127.13, 127.01, 124.80, 124.68, 124.59, 124.46, 124.42, 124.13, 121.87, 121.65, 121.32, 121.16, 121.06, 119.83, 119.50, 119.08, 118.90, 116.84, 116.68, 37.58, 37.29, 36.41, 35.74, 20.92, 20.86, 20.69, 20.65, 20.46, 20.38; ESI-MS (m/z): calcd. for C54H51IrN6: 976.3804, Found [M]+: 976.3954; Elemental analysis result (%): C 66.83, H 5.28, N 8.66 (Calcd (%): C 66.44, H 5.02, N 8.61).
The precursor Compound a was synthesized (yield: ca. 80%).
1H-NMR (300 MHZ, CDCl3) for Compound a: 7.46-7.42 (d, J=11.4 Hz, 4H), 7.28-7.25 (d, J=6.9 Hz, 4H), 2.32 (s, 1H), 1.96 (s, 6H), 1.92 (s, 6H), 1.78 (s, 1H).
Compound a and carbazole were subjected to coupling reaction in the presence of CuI to synthesize Ad-Cz. The reaction mixture was developed/separated through silica column using ether: CH2Cl2 solvent to afford the target compound (yield: 25%). Subsequently, the compound Ad-Cz was purified by sublimation for deposition and was identified to have a purity of 99.9% as analyzed by HPLC (purification yield: 50%).
1H-NMR of compound Ad-Cz (300 MHZ, CDCl3): δ 8.18-8.13 (m, 4H), 7.68-7.49 (m, 6H), 7.43-7.36 (m, 10H), 7.32-7.27 (m, 4H), 2.42 (t, 1H), 2.20 (t, J=11.1 Hz, 6H), 2.09 (t, J=12.3 Hz, 6H), 1.87 (t, J=14.1 Hz, 1H) (Figure S2). 13C-NMR (75.47 MHz, CDCl3): δ 29.65, 35.89, 37.77, 42.32 49.31, 109.94, 120.45, 123.38, 124.21, 125.94, 126.05, 126.91, 129.74, 141.13, 149.72, 152.79. ESI-MS (m/z): calcd. for C46H38N2: 618.3035, Found [M]+: 618.4415.
The Ir complexes synthesized in Comparative Synthesis Examples 1-3 and Synthesis Examples 1-2 were measured for crystal structure, photophysical properties, and electrochemical properties, and calculated for DFT (Density Functional Theory). The results are summarized in Tables 1-6 and depicted in
Ccarbene-Ir-CPh
aD1 means a dihedral angle between the aryl substituent (Ph or diMePh) and the phenyl plane in the coordinated C{circumflex over ( )}C ligand.
bD2 means a dihedral angle between the phenyl plane and the imidazole (NHC) ring in the coordinated C{circumflex over ( )}C ligand
The Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3 were measured for steady-state absorption and emission spectra in CH2Cl2 solution (300 K) and 2-MeTHF (77 K). The measurements are summarized in Tables 2-4 and depicted in
s−1]
s−1]
)3
)3
aValues were measured in an Ar-saturated dichloromethane (CH2Cl2) solution (10 μM) at 300K. The absolute quantum yield was measured through the Quantaurus-QY measurement system (λex = 305 nm) and was integrated over the range of 350-700 nm;
dStrokes shifts were obtained from the following equation: Strokes shift = {dot over (ν)}a-{dot over (ν)}f. As there was no clearly identifiable peak in the absorption spectrum, the absorption value ({dot over (ν)}a) was determined at the edge of the weak absorption tail (350-380 nm) of the Ir complex, which can impart 3MLCT. The position of the absorption edge was determined at the istersection of a straight line adjusted to the right of the absorption shoulder (around 325 nm) and a corrected baseline. {dot over (ν)}f was determined by the first peak of the luminescence spectrum at 300K
indicates data missing or illegible when filed
aValues were measured in an Ar-saturated dichloromethane (CH2Cl2) solution (10 μM) at 300K. The absolute quantum yield was measured through the Quantaurus-QY measurement system (λex = 305 nm) and was integrated over the range of 350-700 nm;
bFilms were prepared on melted silica glass substrate (5 wt % Ir(III) complex), using a solution of poly(methylmethacrylate) (PMMA) in toluene.
cThe values listed are for a 2-MeTHF glassy matrix at 77K;
dStrokes shifts were obtained from the following equation: Strokes shift = {dot over (ν)}a-{dot over (ν)}f. As there was no clearly identifiable peak in the absorption spectrum, the absorption value (ba) was determined at the edge of the weak absorption tail (350-380 nm) of the Ir complex, which can impart 3MLCT. The position of the absorption edge was determined at the intersection of a straight line adjusted to the right of the absorption shoulder (around 325 mm) and a corrected baseline. {dot over (ν)}f was determined by the first peak of the luminescence spectrum at 300K;
eHuang-Rhys factors (S) were determined from the peak heights of the first two features of the 77K luminescence spectrum
The Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3 were measured for HOMO and LUMO energy levels by cyclic voltammetry (CV) (measurement was conducted for the oxidized face in the presence of 0.1 M TBAP in CH2Cl2. scan rate: (100) mV/s), and the results are given in
aHOMO levels were determined using Equation 1 [EHOMO (eV) = −e(Eozpeak ÷ 4.8)] and LUMO levels were determined using Equation 2 [ELUMO (eV) = −e(EHOMOpeak + Egedge)]
bEgedge values were calculated using the wavelength of absorption band edge onset.
cELUMO/EHOMOpeak [eV] (theo.) values were obtained from DFT calculation
For the Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3, DFT calculations (Density Functional Theory calculations) were performed (6-31G basis set for C, H, and N atoms at the B3LYP level; and LANL2DZ basis set for Ir metal in the gas phase). The results are depicted in
In order to understand the triplet excited-state characteristics of the Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3, TD-DFT was performed, and the results are depicted in
Furthermore, the energy diagram of the Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3 is given in
Additionally, the optimized excited-state structures of the meridional Ir complexes synthesized in Synthesis Examples 1-2 and Comparative Synthesis Examples 1-3 were determined through DFT calculations and are depicted in
The mer-Ir(C{circumflex over ( )}CdiMePh)3 synthesized in Synthesis Example 2 was used to fabricate a blue phosphorescent OLED with the structure of ITO (150 nm, anode)/HAT-CN (10 nm)/TAPC (45 nm)/mer-Ir(C{circumflex over ( )}CdiMePh)3 (5 nm) /UGH2: mer-Ir(C{circumflex over ( )}CdiMePh)3 (30 nm, 18%)/UGH2 (5 nm)/TmPyPB (30 nm)/Liq (1 nm)/Al (150 nm, cathode) was fabricated (see
A blue phosphorescent OLED was fabricated in the same manner as in Example 1, with the exception of using mer-Ir(C{circumflex over ( )}CH)3 synthesized in Comparative Synthesis Example 3.
In Example 1 and Comparative Example 1, the singlet/triplet energy levels of each material used in the devices were measured, and the results are presented in
As can be seen in
The OLEDs of Example 1 and Comparative Example 1 were measured for turn-on voltage, power efficiency (PE)—current density (J)—current efficiency (CE) properties, and external quantum efficiency (EQE), and the results are summarized in Table 6 and depicted in
The devices of Example 1 and Comparative Example 1 exhibited similar turn-on voltage values (1 cd/m2), 4.7 V and 4.2 V, respectively (see Table 6).
As can be seen in
As shown in
The devices from Comparative Example 1 and Example 1 displayed CIE chromaticity diagram (x, y) coordinates of (0.17, 0.10) and (0.16, 0.09) respectively, both representing deep blue coordinates. These results suggest that the deep blue emission efficiency of the Ir(C{circumflex over ( )}C)3-type Ir(III) dopant material synthesized with a bulky xylene substituent can be improved for actual application in phosphorescent OLEDs.
mer-Ir(C{circumflex over ( )}CdiMePh)3 synthesized in Synthesis Example 2 and Ad-Cz synthesized in Synthesis Example 3 were used to fabricated blue phosphorescent OLEDs with the structure of ITO (150 nm, anode)/HAT-CN (10 nm)/TAPC (45 nm)/mer-Ir(C{circumflex over ( )}CdiMePh)3 (5 nm)/Ad-Cz: mer-Ir(C{circumflex over ( )}CdiMePh)3 (30 nm, 18%)/Ad-Cz (5 nm)/TmPyPB (30 nm)/Liq (1 nm)/Al (150 nm, cathode). In this regard, use was made of HAT-CN (hexaazatriphenylene-hexacarbonitrile) as a hole injection layer (HIL) material, TAPC (4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzenamine]) as a hole transport layer (HTL) material, TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene) as an electron transport layer (ETL) material, and Liq (8-quinolinolato lithium) as an electron injection layer (EIL) material.
A blue phosphorescent OLED was fabricated in the same manner as in Example 2, with the exception of using Cb-Cz (Exact Mass: 628.19, Molecular Weight: 628.72). The structure of Cb-Cz is as follows.
The host materials used in Example 2 and Comparative Example 2 (Ad-Cz and Cb-Cz) were analyzed for photophysical properties. Steady-state absorption and emission spectra of each material were measured in CH2Cl2 solution. The measurements are summarized in Table 7 and depicted in
To confirm the energy transfer of compound Ad-Cz used as the host in the OLED of Example 2, Sample 1 organic EL was fabricated in the same manner as in Example 2, with the exception of using compound Ad-Cz as the host and FIrpic as the dopant, and was measured for luminance intensity. The results were presented in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0030320 | Mar 2021 | KR | national |
| 10-2022-0029088 | Mar 2022 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/003301 | 3/8/2022 | WO |
