Patent Application
20130153861
The present invention relates generally to organic optoelectronic devices, and more particularly, to organic optoelectronic devices with surface plasmonic structures to enhance their performance and/or their methods of manufacture.
Research in bulk heterojunction (“BHJ”) structures has led to the development of organic photovoltaics devices (“OPVs”) with efficiency close to 9%. Nevertheless, a reliance on indium tin oxide (“ITO”) remains a key limiting factor in the design and performance of OPVs and other organic optoelectronic devices (“OODs”).
ITO as a transparent conductor is known to have several disadvantages and design and performance constraints. First, ITO as used in an OOD is a major cause of device degradation. ITO has a tendency to crack or break when deposited on flexible substrates and subjected to bending. The formation and propagation of cracks in the ITO in turn increase its electrical resistance, resulting in a loss of conductivity. ITO tends to degrade over time, permitting oxygen and moisture to diffuse into the organic layers of the OOD and adversely affecting the DOD's operational lifetime. A further disadvantage of ITO is cost. ITO requires indium, which due to scarcity has high material cost that prevents the wide deployment of ITO in cost-conscious industries, such as in the OPV industry. ITO also suffers from the compromise between conductivity and transparency. During ITO film deposition, the high concentration of charge carriers increases the conductivity of the ITO, but decreases its transparency, which is undesirable, as OODs typically require both high anode conductivity and transparency to deliver optimal device performance.
Although transparent films of carbon nanotubes or highly conductive polymers have been proposed as replacements to ITO, the performance of OPVs and other OODs have not been substantially enhanced to date as a result.
A need, therefore, exists for an alternative optically transmissive conductor suitable for application in OODs without the disadvantages associated with ITO materials.
In accordance with a first aspect, an organic optoelectronic device is disclosed. The organic optoelectronic device includes a carrier substrate, a metal anode electrode layer disposed at least partially on the carrier substrate, an organic electronic active region including one or more organic layers and disposed at least partially on the metal anode electrode layer, and a cathode electrode layer disposed at least partially on the organic photoactive layer. The metal anode electrode layer includes periodic arrays of sub-wavelength nanostructures.
In accordance with an additional aspect, a method of manufacturing an organic optoelectronic device is also disclosed. The method of manufacturing an organic optoelectronic device includes forming a metal anode electrode layer at least partially on a carrier substrate; forming a periodic array of sub-wavelength nanostructures in the metal anode electrode layer defined as the perforated metal anode electrode layer; forming an organic electronic active region at least partially on the perforated metal anode electrode layer, the organic electronic active region comprising one or more organic layers; and forming a cathode electrode layer at least partially on the organic electronic active region.
In accordance with a further aspect, a method of manufacturing an organic photovoltaic device is disclosed. The method of manufacturing an organic photovoltaic device includes the steps of: determining a peak optical absorption wavelength of an organic photoactive layer to be formed at least partially on a metal anode electrode layer; defining a desired peak optical transmission wavelength of a periodic array of sub-wavelength nanostructures adapted to be formed in the metal anode electrode layer based on said determined peak optical absorption wavelength of said organic photoactive layer; determining a desired periodicity of said periodic array of sub-wavelength nanostructures based at least in part on said desired peak optical transmission wavelength of said periodic array of sub-wavelength nanostructures, a dielectric constant of said carrier substrate, and a dielectric constant of said metal anode electrode layer; defining a desired optical transmission bandwidth of said periodic array of sub-wavelength nanostructures based on an optical absorption bandwidth of said organic photoactive layer; and defining a desired geometry of each of said nanostructures and a desired thickness of said metal anode electrode layer based on said desired optical transmission bandwidth of said periodic array of sub-wavelength nanostructures
Following the preceding steps, the method of manufacturing an organic photovoltaic device proceeds to forming said metal anode electrode layer with said desired thickness at least partially on a carrier substrate; forming said periodic array of sub-wavelength nanostructures in said metal anode electrode layer with said desired geometry for each of said nanostructures and with said desired periodicity; forming organic layers with at least one being photoactive at least partially on said metal anode electrode layer; and forming a cathode electrode layer at least partially on said organic photoactive layer.
In accordance with a yet further aspect, a method of manufacturing an organic light emitting diode device is disclosed. The method of manufacturing an organic light emitting diode device includes the steps of: determining a peak optical emission wavelength of an organic emissive electroluminescent layer to be formed at least partially on a metal anode electrode layer; defining a desired peak optical transmission wavelength of a periodic array of sub-wavelength nanostructures adapted to be formed in the metal anode electrode layer based on said determined peak optical emission wavelength of said organic emissive electroluminescent layer; determining a desired periodicity of said periodic array of sub-wavelength nanostructures based at least in part on said desired peak optical transmission wavelength of said periodic array of sub-wavelength nanostructures, a dielectric constant of said organic photoactive layer, and a dielectric constant of said metal anode electrode layer; defining a desired optical transmission bandwidth of said periodic array of sub-wavelength nanostructures based on an optical transmission bandwidth of said organic emissive electroluminescent layer; and defining a desired geometry of each of said nanostructures and a desired thickness of said metal anode electrode layer based on said desired optical transmission bandwidth of said periodic array of sub-wavelength nanostructures.
Following the preceding steps, the method of manufacturing a light emitting diode device proceeds to forming said metal anode electrode layer with said desired thickness at least partially on a carrier substrate; forming said periodic array of sub-wavelength nanostructures in said metal anode electrode layer with said desired geometry for each of said nanostructures and with said desired periodicity; forming organic layers with at least one being an emissive electroluminescent layer at least partially on said metal anode electrode layer; and forming a cathode electrode layer at least partially on said organic emissive electroluminescent layer.
In accordance with another embodiment of the present invention, an organic optoelectronic device is provided, comprising: a carrier substrate; a cathode electrode layer disposed at least partially on the carrier substrate, the cathode electrode layer having a periodic array of sub-wavelength nanostructures; an organic electronic active region disposed at least partially on the cathode electrode layer, the organic electronic active region comprising one or more organic layers; and an anode electrode layer disposed at least partially on the organic photoactive layer.
Further advantages of the invention will become apparent when considering the drawings in conjunction with the detailed description.
The organic optoelectronic device and the method of manufacturing an OOD of the present invention will now be described with reference to the accompanying drawing figures, in which:
Further advantages of the invention will become apparent when considering the drawings in conjunction with the detailed description.
Similar reference numerals refer to corresponding parts throughout the several views of the drawings.
In one embodiment of the present invention, an ordered or periodic array of sub-wavelength nanostructures is optimally formed in a metal layer, such as an exemplary metallic foil or film, for use as an anode in an organic optoelectronic device (“OOD”), such as in an organic photovoltaic device (“OPV”) or an organic light emitting diode device (“OLED”), for example. The metal anode layer comprising one or more nanostructures may be desirably adapted for use in an OOD as a replacement or alternative to a conventional high work function, optically-transmissive front electrode, which is typically made of indium tin oxide (“ITO”). As compared to conventional ITO-OODs, the ITO-free OOD configuration of the present invention leverages the relatively higher conductivity of metal as the anode materials (e.g. silver (Ag), gold (Au), and copper (Cu)), and the Surface Plasmonic (“SP”) and Extraordinary Optical Transmission (“EOT”) properties observed in the perforated metal anode electrode layer to desirably increase OOD device efficiency.
EOT is a strong enhancement of optical transmission observed when a metal film is perforated with an array of holes having sub-wavelength-geometries. The phenomenon of EOT has been identified as the result of the interaction of Surface Plasmons (“SPs”) with photons. SPs are typically understood to be the oscillations of free electrons at the interface of a metal and a dielectric. Photons incident at the interface between the metal and dielectric layers interact resonantly with and cause excitation of the SPs, whereby the SPs couple with the photons to form surface plasmon polaritons (“SPP”). It has been shown that SPPs cause incident light to transmit through a metal film perforated with an array of sub-wavelength holes and a strong enhancement of optical transmission is observed for a specified wavelength range of the light transmitted through the sub-wavelength holes in the metal film material.
One embodiment of the invention applies the principles of SP and EOT in an OOD to configure the optical transmission properties of a fully or partially perforated metal anode electrode layer such that the maximum amount of useful photons are exploited to effect the operation of the OOD, as will be discussed later in detail. As compared to a conventional ITO-based OOD, the end result of such an embodiment of the invention is effectively an OOD comprised of a metal anode layer with nanostructures that advantageously resists against OOD device degradation, and provides higher anode conductivity, lower manufacturing costs, and fewer manufacturing steps. Certain embodiments of the OOD of the invention adapted for OPV applications also exhibit significantly higher power conversion efficiencies compared to conventional ITO-OPVs.
The present invention will now be further described with reference to the Figures.
As used herein, a “layer” of a given material includes a region of that material the thickness of which is smaller than either of its length or width. Examples of layers may include sheets, foils, films, laminations, coatings, blends of organic polymers, metal plating, and adhesion layer(s), for example. Further, a “layer” as used herein need not be planar, but may alternatively be folded, bent or otherwise contoured in at least one direction, for example.
Still referring to
The organic electronic active region 120 of the OOD 100 includes one or more organic layers. The specific materials selected to form the organic layers of the organic electronic active region 120 depend on the particular construction of the OOD 100, which may be an OPV 101 or an OLED 102 as shown in respective
The cathode electrode layer 110 of the OOD 100 may comprise of any suitable low work function cathode electrode materials, such as Indium (In), calcium/aluminum (Ca/Al), aluminum (Al), lithium fluoride (LiF), and aluminum oxide/aluminum (Al2O3/Al)), for example.
Referring to
As used herein, “sub-wavelength” nanostructures (e.g. nanoholes 144) refer to nanoholes and/or other nanostructures such as nano-slits or slots, where at least one geometric dimension of the nanostructures is less than a wavelength of the photons (e.g. sun light and/or artificial light) incident on the periodic array 142 at the interface 180 between metal anode electrode layer 140 and the carrier substrate 150.
Still referring to
The periodic array 142 of sub-wavelength nanoholes 144 may be formed in the metal anode electrode layer 140 by any suitable known technique capable of producing sub-wavelength nanoholes in a periodic pattern, such as by known milling techniques (e.g. focused ion beam (“FIB”) milling), lithography techniques (e.g. nano-imprint lithography, deep UV lithography, and electron beam lithography), hot stamping, and embossing, or combinations thereof, for example. In one embodiment, the nanoholes 144 may be defined in the metal anode electrode layer 140 using a FIB process such as by use of a Strata 235 Dualbeam Scanning Electron Microscope (“SEM”)/FIB. Gallium ions (Ga+) may be used as the FIB implantation source in one such embodiment, for example.
Having generally described the components of the OOD 100 according to the invention, the specific features of these components are now described in reference to the particular construction of the OOD 100.
Referring to
In an optional embodiment, the organic active electronic region 120 may further include a hole transport layer (not shown) disposed between the anode electrode layer 140 and the photoactive layer 122, as known in the art. The hole transport layer is comprised of organic hole transport material that facilitates the transport of electron holes from the organic photoactive layer 122 to the anode electrode layer 140.
Suitable materials for the cathode electrode layer 110, the anode electrode layer 140, and the carrier substrate 150 of the OPV 101 may be similarly selected from the same list of exemplary materials for the respective corresponding layers as discussed above in connection with OOD 100.
In a preferred embodiment, the OPV 101 is a bulk heterojunction OPV, and exemplary organic photoactive materials of the organic photoactive layer 122 may include a photoactive electron donor-acceptor blend such as poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM), for example. Exemplary hole transport materials for the hole transport layer may include conductive polymers, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (“PEDOT:PSS”), for example. However, it is understood that other suitable compounds may be employed as one or more exemplary organic photoactive materials in particular exemplary embodiments, such as PDCTBT (Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]):PC70BM ([6,6]-phenyl-C61-butyric acid methyl ester), or other suitable photoactive materials known in the art, for example.
In use, OPV 101 is configured to receive electromagnetic energy (e.g. light 161) incident to or at the underside or bottom side of OPV 101 as shown in
In one embodiment, the peak optical transmission intensity and/or wavelength and the optical transmission bandwidth of the periodic array 142 may be configured to correspond or match the peak absorption intensity and/or wavelength and the optical absorption bandwidth of the photoactive layer 122, thereby ensuring the maximum amount of photons useful for photovoltaic conversion may be transmitted through the nanoholes 144 and be absorbed at the photoactive layer 122. In that sense, the periodic array 142 operates to enhance optical absorption at the photoactive layer 122, and functions as a spectral filter to filter or block harmful radiation, such as ultraviolet (UV) wavelengths, which have been shown to degrade the organic photoactive layer 122 and reduce the operational lifetime of the OPV 101.
Referring to
λSP(i,j)=p sqrt(emed)/[sqrt(i2+j2)sqrt(ed+em)] (1)
In the above-noted equation, λSPP(i,j) is the (first order) peak optical transmission wavelength of the periodic array 142 or the peak wavelength of the SP resonance modes on the nanoholes 144 for a square lattice when the incident light 161 is normal to the plane of the periodic array 142; p is the periodicity of the array 142; ed and em are the dielectric constants of the metal-dielectric interface 180 and metal anode layer 140 respectively; and indices i and j are integers representing the peak orders.
Further, the desired geometry d and the desired depth or height h of each of said nanoholes 144 in the metal anode layer 140 (the latter of which corresponds to the thickness t of the metal anode electrode layer 140) are based or dependent on the desired optical transmission bandwidth of the periodic array 142, which in the case of an OPV 101 may be preferably selected to correspond to the optimal optical absorption bandwidth of the organic photoactive layer 122 as discussed above.
In a particular embodiment, the periodic array 142 as used in the OPV 101 may comprise nanoholes 144 each of which have a characteristic geometric dimension d of about 100 nanometers (nm), a height h in the metal anode layer 140 of about 105 nm, and a periodicity of about 450 nm. In other embodiments, the periodic array 142 of the OPV 101 may generally have a periodicity between about 400 nm and about 600 nm.
As shown in
Suitable materials for the organic emissive electroluminescent layer 126 may comprise any one of several known light-emitting dyes or dopants dispersed in a suitable host material, photosensitizing materials, and/or light-emitting polymer materials, for example.
In another embodiment, the organic active electronic region 120 may further include a hole transport layer (not shown) disposed at least partially between an exemplary metal anode electrode layer 140 and the emissive electroluminescent layer 126, as is known in the art. The hole transport layer may advantageously be provided to assist in the transfer of positive charges or “holes” from the metal anode electrode layer 140 to the emissive electroluminescent layer 126, for example. In other embodiments, the organic active electronic region 120 may include additional organic layers (not shown) advantageously provided to assist in the transfer of electrons from the cathode electrode layer 110 to the emissive electroluminescent layer 126, for example, as is known in the art.
Suitable materials for the cathode electrode layer 110, the anode electrode layer 140, and the carrier substrate 150 of the OLED 102 may be similarly selected from the same exemplary list of materials for the respective corresponding layers as discussed above in connection with OOD 100.
In use, the OLED 102 is configured such that upon application of an external electrical field on the electrode layers 110 and 150, the organic emissive electroluminescent layer 126 emits electromagnetic radiation, such as light 162. In one embodiment, the OLED 102 may be configured to be bottom emissive such that the light 162 emitted by the organic emissive electroluminescent layer 126 transmits through the nanoholes 144 in the metal anode electrode layer 140 and exits the OLED 102 through the carrier substrate 150 to thereby effect illumination. The optical transmission properties of the periodic nanohole array 142, including the wavelength of the peak optical transmission, the intensity of the transmitted light at the peak, and the optical transmission bandwidth, may be desirably configured such that the optical transmission properties (e.g. optical transmission spectrum) of the periodic nanohole array 142 corresponds to or matches with the optical emission properties (e.g. the optical emission spectrum) of the organic emissive electroluminescent layer 126, such that the specific wavelengths (colors) at which the light 162 is emitted by the organic emissive electroluminescent layer 126 may transmit through the otherwise optically opaque metal anode electrode layer 140, thereby resulting in an ITO-free OLED 102 based on a metal anode electrode layer 140 perforated with a periodic array 142 of nanoholes 144 that is desirably lower in cost and better protected from the effects of moisture and oxygen diffusion on the organic layers and desirably also enjoys an overall increase in device performance, as compared to a conventional ITO-OLED.
In one embodiment, the optical transmission properties of the periodic nanohole array 142 of the OLED 102 may be configured such that the intensity of the light 162 emitted by the organic emissive electroluminescent layer 126 and transmitted through the nanoholes 144 is enhanced, thereby resulting in an increased apparent “brightness” in OELD 102 illumination. Such enhanced optical emission may be achieved by configuring the optical transmission properties of the periodic nanohole array 142 of the OLED to match with or correspond to the similar optical emission properties of the organic emissive electroluminescent layer 126 (e.g. wavelength of the peak optical emission, the intensity of the emitted light at the peak, and the optical emission bandwidth).
The desired periodicity p of the periodic array 142 of the OLED 102 may similarly be governed by equation (1) as discussed above in connection with OPV 101.
The desired geometric dimension d and the desired depth or height h of each of said nanoholes 144 in the metal anode layer 140 of the OELD 102 are similarly based or dependent on the desired optical transmission bandwidth of the periodic array 142, which in the case of an OLED 102 may be desirably selected to correspond with the optical emission bandwidth of the organic emissive electroluminescent layer 126 as discussed above.
In an alternative embodiment, an OOD according to an embodiment of the present invention may comprise an inverse configuration wherein a cathode layer is disposed at least partially on a suitable carrier substrate, a suitable organic electronic active region (which may comprise at least one of an active layer and a hole transport layer) is disposed at least partially on the cathode layer, and an anode layer is disposed at least partially on the organic photoactive layer.
The geometries and arrangement patterns of the sub-wavelength nanostructures formed in the metal anode electrode layer 140 may depend, at least in part, on the intended use of the organic optoelectronic device 100 and the desired optical transmission properties of the sub-wavelength nanostructures. In one embodiment, for example, sub-wavelength nanostructures may comprise substantially circular holes, such as nanoholes 144 as described above in reference to
Embodiments of the sub-wavelength nanostructures configured with additional exemplary periodic patterns and geometries are now described with reference to
Preferably, each of the annular rings 1603 are formed by a plurality of nanoholes 1607 arranged in a single ring concentrically disposed about its corresponding central hole 1601, similar to the manner the annular rings 1303 are formed by arranging nanoholes 1307 in concentric rings as shown in
As described herein, each annular ring 1603 with its corresponding central hole 1601 may be defined as a unitary cell 1609, such that the periodic pattern 1600 can be said to be comprised of a plurality of periodically arranged unitary cells 1609. In the embodiment as shown, the unitary cells 1609 are arranged in a hexagonal lattice configuration. Other periodic patterns for arranging the unitary cells 1609 may be selected however, such as a hexagonal, square, rhombic, rectangular, and parallelogrammatic lattice, for example.
For example, in one embodiment where the sub-wavelength nanostructures are adapted to be formed in a metal anode electrode layer of an OLED (e.g. OLED 102 of
Similarly, if the light emitted by the OLED 102 is desired to have a specific, predefined wavelength(s), the sub-wavelength nanostructures may be configured with a suitable periodic pattern, such as periodic patterns 1200 (curve 2200) and 1302 (curve 2302), such that the light emitted by the organic emissive electroluminescent layer 126, upon transmission through the sub-wavelength nanostructures, is altered or tuned to have a relatively narrow bandwidth corresponding to the desired, predefined wavelength(s).
In another embodiment where the light emitted by the OLED 102 is not required to have a specific, predefined wavelength(s), the sub-wavelength nanostructures may be arranged in a suitable periodic pattern, such as periodic patterns 1300 (curve 2300), such that the light emitted by the organic emissive electroluminescent layer 126, upon transmission through the sub-wavelength nanostructures, is altered or tuned to have a relatively high illumination intensity, which may desirably correspond to an effective overall increase in efficiency of the OLED 102.
In one embodiment where the sub-wavelength nanostructures are adapted to be formed in a metal anode electrode layer of an OPV (e.g. OPV 101 of
In one embodiment where the OPV 101 has a low band gap, and therefore has a relatively wider spectrum of photon absorption, the sub-wavelength nanostructures may be similarly configured to have a relatively wide optical transmission spectrum to match the absorption spectrum of the organic photoactive layer 122 of the OPV 101, such that the maximum amount of useful photons are exploited to improve the overall power and/or efficiency of the OPV 101. In such embodiment, the sub-wavelength nanostructures may be arranged in a suitable periodic pattern, such as periodic patterns 1300, 1400, 1500, 1600 (corresponding to spectrogram curves 2300, 2400, 2500, 2600, respectively), such that light 161 incident on the OPV 101, upon transmission through the sub-wavelength nanostructures in the metal anode electrode layer 140, is tuned or altered to have the desired relatively wide transmission spectrum.
Referring now to
The metal anode electrode layer 140 may be formed on the carrier substrate 150 by any suitable means or method so as to deposit, attach, adhere or otherwise suitably join the metal anode electrode layer 140 to at least a portion of the top surface of the carrier substrate 150. In one embodiment, the metal anode electrode layer 140 may be formed on the carrier substrate 150 by any suitable deposition techniques, including physical vapor deposition, chemical vapor deposition, epitaxy, etching, sputtering and/or other techniques known in the art and combinations thereof, for example. Typical anode materials for the metal anode electrode layer 140 are listed above in the section for the “OOD 100” with reference to
In an exemplary embodiment of the method 500 adapted for OPV 101 fabrication, the anode material for the metal anode electrode layer 140 is selected from thin films of chromium (Cr)/silver (Ag) with thickness of 5 nm and 100 nm, respectively, and are deposited on the carrier substrate 150 by sputtering.
Next, the method 500 proceeds with forming a periodic array 142 of sub-wavelength nanostructures (e.g. nanoholes 144) in the metal anode electrode layer 140, as shown at operation 520. As discussed above, the periodic array 142 of sub-wavelength nanoholes 144 may be formed in the metal anode electrode layer 140 by any suitable known technique capable of producing sub-wavelength nanoholes in a periodic pattern, such as known milling techniques (e.g. focused ion beam (“FIB”) milling), lithography techniques (e.g. nano-imprint lithography, deep UV lithography, and electron beam lithography), hot stamping, and embossing, or the combinations thereof, for example. In an exemplary embodiment of the method 500 adapted for OPV 101 fabrication, nanoholes 144 fabrication is performed using FIB milling, such as with a Strata™ 235 Dualbeam Scanning Electron Microscope (“SEM”)/Focused Ion-Beam (“FIB”). Multiple periodic arrays 142 of approximately 100 nm in geometry and with 450 nm periodicity are then milled into the 105 nm metal anode layer 140 (e.g. film) using a Gallium ion (Ga+) source of the FIB. Nanohole areas of approximately 1 mm2 are subsequently created by serially milling multiple 625 μm2 periodic arrays 142 at a magnification of ×5000.
The particular geometrical parameters of the periodic array 142 (e.g. periodicity p) and the nanoholes 144 (e.g. hole geometry d and hole height h) may be pre-defined prior to the commencement of the method 500, and may be pre-defined according to the preliminary steps for the fabrication of an OPV 101 as illustrated in
In some embodiments, the method 500 may additionally include a baking or annealing step, which may optionally be conducted in a controlled atmosphere, such as to optimize the photo-conversion of the organic active region 122, for example.
Next, as shown at operation 530, the method 500 proceeds to forming an organic electronic active region 120 on the perforated metal anode electrode layer 146. The organic electronic active region 120 includes one or more organic layers.
In one embodiment in which the method 500 is particularly adapted to optimally manufacture an OPV (e.g. OPV 101), the organic electronic active region 120 includes a photoactive layer 122. The operation 530 of forming an organic electronic active region 120 on the metal anode electrode layer 140 includes forming the organic photoactive layer 122 on the perforated metal anode electrode layer 146. The organic photoactive layer 122 may be formed on the perforated metal anode electrode layer 146 at operation 530 by any suitable organic film deposition techniques, including, but not limited to, spin coating, spraying, printing, brush painting, molding, and/or evaporating on a photoactive material on the perforated metal anode electrode layer 146 to form the organic photoactive layer 122, for example. Exemplary suitable organic photoactive materials are listed above in the section for the “OPV 101” with reference to
In one embodiment in which the method 500 is particularly adapted to manufacture an OLED (e.g. OLED 102), the organic electronic active region 120 includes an organic emissive electroluminescent layer 126. The operation 530 of forming an organic electronic active region 120 on the metal anode electrode layer 140 alternatively includes forming the organic emissive electroluminescent layer 126 on the perforated metal anode electrode layer 146. The organic emissive electroluminescent layer 126 may similarly be formed on the perforated metal anode electrode layer 146 at operation 530 by any suitable organic film deposition techniques, including, but not limited to, spin coating, spraying, printing, brush painting, molding, and/or evaporating on a photoactive material on the perforated metal anode electrode layer 146 to form the organic emissive electroluminescent layer 126, for example. Exemplary suitable materials for the organic emissive electroluminescent layer 126 may comprise any one of several known light-emitting dyes or dopants dispersed in a suitable host material, photosensitizing materials, and or light-emitting polymer materials, for example, as are known in the art.
Following the formation of the organic electronic active region 120 on the perforated metal anode electrode layer 140 at operation 530, the method 500 proceeds to operation 540 at which a cathode electrode layer 110 is formed at least partially on the organic electronic active region 120, thereby completing the fabrication of the OOD 100. Similar to the metal anode electrode layer 140, the cathode electrode layer 110 may be formed on the organic electronic active region 120 by any suitable means or method so as to deposit, attach, adhere or otherwise suitably join the cathode electrode layer 110 to at least a portion of the top surface of the organic layer(s) of the organic electronic active region 120. In one embodiment, the cathode electrode layer 110 may be formed on the organic electronic active region 120 by any suitable deposition techniques, including physical vapor deposition, chemical vapor deposition, epitaxy, etching, sputtering and/or other techniques known in the art and combinations thereof, for example.
In an exemplary embodiment of the method 500 adapted for OPV 101 fabrication, the cathode electrode layer 110 is made of aluminum with preferably a thickness of approximately 100 nm, and is deposited on the P3HT:PCBM organic photoactive layer 122 by thermal evaporation.
Other method embodiments of the method 500 of manufacturing an OOD have been contemplated. For example, in an embodiment in which the method 500 is particularly adapted to manufacture an OPV (e.g. OPV 101 shown in
In some embodiments, prior to the commencement of the method 500 as shown in
Referring to
As shown in
Next, at operation 620, a desired peak optical transmission wavelength of the periodic array 142 adapted to be formed in the metal anode electrode layer 140 is defined based on the peak optical absorption wavelength of the organic photoactive layer 122 determined at operation 610. In an exemplary embodiment of OPV 101 fabrication, the metal anode electrode layer 140 is selected to be a silver anode layer. Therefore, at operation 620, a desired peak optical transmission wavelength of the periodic array 142 adapted to be formed in this silver metal anode electrode layer 140 is defined to preferably match the peak optical absorption wavelength of the organic photoactive layer 122 determined at operation 620, or 500 nm.
Following operation 620, a desired periodicity p of the periodic array 142 is determined at operation 630 based at least in part on the desired peak optical transmission wavelength of the periodic array 142 determined at 620, a dielectric constant of the carrier substrate 150, and a dielectric constant of the metal anode electrode layer 140. The periodicity of the periodic array 142 may be determined based on the first order approximation of the peak optical transmission wavelength λSP(i,j) of the periodic array 142 set forth in equation (1) above, with all the other parameters in equation (1) being known. In an exemplary embodiment of OPV 101 fabrication, the desired periodicity p at which the peak transmission wavelength of the periodic array 142 formed in the silver anode layer 140 is closest to the peak absorption wavelength of the P3HT:PCBM organic photoactive layer 122 is computed from equation (1) to be 450 nm.
Next, at operation 640, a desired optical transmission bandwidth of the periodic array 142 is defined based on an optical absorption bandwidth of the organic photoactive layer 122. In an exemplary embodiment of OPV 101 fabrication, the optical absorption bandwidth of the P3HT:PCBM organic photoactive layer 122 is known to correspond to the green region of the visible spectrum, between 400 nm to 650 nm. Accordingly, the desired optical transmission bandwidth of the periodic array 142 is selected to fall within the visible and near-infrared regions of the electromagnetic spectrum, or between 380 nm to 650 nm, which includes the green region of the visible spectrum corresponding to the optical absorption bandwidth of the P3HT:PCBM organic photoactive layer 122.
Following operation 640, a desired diameter d of each of the nanoholes 144 and a desired thickness t of the metal anode electrode layer 140 are defined based on the desired optical transmission bandwidth of the periodic array 142, as shown at operation 650. It is known that the nanohole periodicity p and metal anode type are dependent on the peak optical transmission wavelengths, or the specific wavelengths of light that will resonate and transmit through nanohole arrays. It is further known that the optical transmission bandwidth of the period array 142 is dependent on the nanohole diameter d and metal thickness t. Accordingly, in an exemplary OPV 101 fabrication, based on the desired optical transmission bandwidth of the periodic array 142, which is determined from operation 640 to be between 380 nm to 850 nm, the diameter d of each of the nanoholes 144 and the desired thickness t of the silver anode electrode layer 140 are defined to be 100 nm and about 105 nm, respectively.
Following operation 650, the preliminary steps for pre-defining the geometric parameters of the periodic array 142 and the sub-wavelength nanoholes 144 are completed. The method 500 illustrated in
Following operation 510, the periodic array 142 may be formed during operation 520 in the metal anode electrode layer 140 with the desired diameter d (determined at operation 650) for each of the nanoholes 144 and with the desired periodicity p (determined at operation 630), which in the exemplary OPV 101 fabrication are determined to be 100 nm and 450 nm for diameter d and periodicity p, respectively.
Following operation 520, the method 500 proceeds to steps 530 and 540 to complete the OPV 101 fabrication as shown in
Referring to
As noted above, for OLED 102 fabrication, the optical properties of the periodic array 142 is preferably defined to match or correspond with the optical properties of the organic emissive electroluminescent layer 126 in the OLED 102 to thereby allow the specific wavelengths (colors) at which the light 162 is emitted by the organic emissive electroluminescent layer 126 to transmit through the otherwise optically opaque metal anode electrode layer 140. The steps as shown in
Referring still to
Next, at operation 720, similar to operation 620 adapted for OPV 101 fabrication, a desired peak optical transmission wavelength of the periodic array 142 adapted to be formed in the metal anode electrode layer 140 for OLED 102 fabrication is based on the peak optical emission wavelength of the organic emissive electroluminescent layer 126 determined at operation 710.
Following operation 720, a desired periodicity p of the periodic array 142 is determined at operation 730 based at least in part on the desired peak optical transmission wavelength of the periodic array 142 determined at 720, a dielectric constant of the carrier substrate 150, and a dielectric constant of the metal anode electrode layer 140. The periodicity of the periodic array 142 may be determined based on the first order approximation of the peak optical transmission wavelength λSP(i,j) of the periodic array 142 set forth in equation (1) above, similar to that as described in operation 630.
Next, at operation 750, a desired optical transmission bandwidth of the periodic array 142 of the OLED 102 is defined based on an optical emission bandwidth of the organic emissive electroluminescent layer 126, after which a desired diameter d of each of the nanoholes 144 and a desired thickness h of the metal anode electrode layer 140 may be defined based on the desired optical transmission bandwidth of the periodic array 142, as shown at operation 760.
Following operation 760, the preliminary steps for pre-defining the geometrical parameters of the periodic array 142 and the sub-wavelength nanoholes 144 for OLED 102 fabrication are completed, and the method 500 illustrated in
Accordingly, as described, the OOD 100 and the particular exemplary OPV 101 and OLED 102 constructions (the “Devices”), and the method of manufacturing an OOD 100, which may be particular adapted to manufacture an OPV 101 and OLED 102 (the “Methods”), may advantageously be used to improve on conventional ITO-based OODs. The Devices and Methods according to embodiments of the invention may desirably provide at least one or more of the following advantages:
Certain embodiments of the perforated metal anode electrode layer 146-based Devices and Methods may desirably cost less to manufacture than prior art ITO-based OODs due to the lower metal anode materials (e.g. Au, Ag, and Cu) cost as compared to ITO. Further, as compared to prior art ITO-based OODs which may require additional protective layers in order to protect against the effect of harmful UV wavelengths that may penetrate through the transparent ITO conductor and adversely impact on the organic layers, the perforated metal anode electrode layer 146 may be configured to function as a spectral filter to block or reflectively filter harmful UV without the addition of additional protective layers, thereby lowering the manufacturing costs and simplifying the manufacturing process.
As compared to the rigid nature of ITO used in prior art OOD applications which may be susceptible to cracking upon bending and the tendency for ITO to degrade or decompose after prolonged use, both of which may result in the penetration of oxygen and moisture into the organic layers, the metal anode materials used in certain embodiments of the Methods and Devices may desirably provide oxygen and moisture resistance and thereby prolong OOD device operational lifetime.
The prior art devices using ITO compromise between conductivity (carrier mobility) and optical transmission. The anode materials selected to form the perforated metal anode layer 146 according to the Devices and Methods embodiments of the invention may be selected from conductive metals such as Ag, Au, and Cu, and may be further configured for enhanced optical transmission, thereby effectively avoiding the comprise which exists in conventional ITO-OODs.
As applied to OPV 101 device fabrication, certain Devices and Methods of the embodiments of the invention have shown an increase in higher power output and/or power conversion efficiency as compared to an ITO-based OPV. In certain embodiments as applied to OLED 102, the optical transmission properties of the period nanohole array 142 of the OLED 102 may be configured such that the intensity of the light 162 emitted by the organic emissive electroluminescent layer 126 and transmitted through the nanoholes 144 are enhanced, thereby resulting in an increased apparent “brightness” in OLED 102 illumination and efficiency as compared to a conventional ITO-OLED.
In one embodiment of the invention, to determine whether the 450 nm nanohole periodicity theoretically determined at operation 620 shown in the preliminary configuration steps of
As discussed below with reference to
Referring to
For comparison with AgSPP fabricated on glass carrier substrates 150 shown in
As shown in
Referring now to
In another exemplary embodiment, current density-voltage (J-V) characteristics for the ITO-OPV and perforated silver anode layers based OPVs devices (hereinafter “AgSPP-OPVs”) on glass respectively, were determined. In such an embodiment, ITO (100 nm thick ITO, 20 Ω/cm2) may be made in substantially the same process as making the exemplary OPV 101 as discussed with reference to
In particular exemplary embodiments of the present invention, periodic nanofeature arrays embodying any suitable desired periodicity or spacing may be formed on OPV cells according to the present invention and arranged in any suitable or desired formation or pattern. In one such embodiment, periodic nanohole arrays may comprise one or more of: triangular, square, hexagonal or any other desired polygonal grid patterns, circular or concentric circular patterns, or circular slot or concentric circular slot patterns, for example.
The exemplary embodiments herein described are not intended to be exhaustive or to limit the scope of the invention to the precise forms disclosed. They are chosen and described to explain the principles of the invention and its application and practical use to allow others skilled in the art to comprehend its teachings.
As will be apparent to those skilled in the art in light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.
