Patent Application
20220148817
This application claims the priority benefit of Taiwan application serial no. 109139286, filed on Nov. 11, 2020. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The disclosure relates to a photoelectrochromic device (PECD) technique, and in particular, to a photoelectrode with independent separate structures of an electrochromic layer and a sensitized light-absorbing layer, and a photoelectrochromic device having fast coloring/bleaching characteristics.
The current photoelectrochromic device (PECD) systems are limited by the transmittance of the photoactive layer, the selection of the electrochromic material, the type and concentration of the electrolyte, and the differences in structure. Therefore, high optical contrast and fast response time as in conventional electrochromic devices cannot be achieved.
To address the above issues, a separated type PECD (S-PECD) in which the electrochromic layer and the sensitized light-absorbing layer are respectively fixed on the surfaces of the photoelectrode and the counter electrode, and a combined type PECD (C-PECD) in which the electrochromic layer and the sensitized light-absorbing layer are combined together on the surface of the photoelectrode have been developed. Compared with the separated type PECD, the combined type PECD exhibits better coloring/bleaching response time because of a different operation mechanism. However, due to the high temperature process for preparing the photoelectrode, the current combined type PECD studies use inorganic electrochromic materials. Although such materials have the advantage of high stability, due to the low coloration efficiency (<100 cm2 C−1) and high electron transfer resistance, the response time of the combined type PECD generally falls in the range of hundreds of seconds, and thus the original advantage of this structure is lost.
On the other hand, the separated type PECD is the most complete structure currently known and developed. This structure is characterized by the dual-function electrode of inorganic composite material/conductive polymer on the counter electrode. By improving the photovoltaic performance of the PECD, the optical contrast is increased and the coloring/bleaching response time is shortened. However, when the catalytic ability on the counter electrode increases, it means that the electrode will tend to transfer the electrons of the colored electrochromic material to the electrode surface to carry out the I3− reduction reaction, which results in a decrease in the degree of the reduced state (lighter colored state) and affects the overall optical contrast of the PECD.
The disclosure provides a photoelectrode with independent separate structures of an electrochromic layer and a sensitized light-absorbing layer, which can reduce electron transfer resistance and increase the selectivity of the electrochromic layer.
The disclosure also provides a photoelectrochromic device, which exhibits fast coloring/bleaching characteristics and solves the issue of insufficient optical contrast of a dual-function electrode.
A photoelectrode with independent separate structures of an electrochromic layer and a sensitized light-absorbing layer according to the disclosure includes a first transparent conductive substrate, a first electrochromic layer, and a sensitized light-absorbing layer. The first electrochromic layer and the sensitized light-absorbing layer are disposed on a surface of the first transparent conductive substrate and are adjacent to each other.
In an embodiment of the disclosure, a distance between the first electrochromic layer and the sensitized light-absorbing layer is 0.05 cm or less.
In an embodiment of the disclosure, the first electrochromic layer and the sensitized light-absorbing layer are in direct contact with each other and do not overlap with each other.
A photoelectrochromic device according to the disclosure includes the above photoelectrode, a counter electrode plate, and an electrolyte. The photoelectrode includes the first electrochromic layer and the sensitized light-absorbing layer adjacent to each other. The counter electrode plate includes a second transparent conductive substrate, and a second electrochromic layer or a metal layer disposed on a surface of the second transparent conductive substrate. The electrolyte is located between the photoelectrode and the counter electrode plate.
In another embodiment of the disclosure, a material of the first electrochromic layer and a material of the second electrochromic layer each independently include a transition metal oxide, a metal cyanide, an organic small molecule compound, or a conductive polymer.
In another embodiment of the disclosure, a material of the first electrochromic layer and a material of the second electrochromic layer each independently include poly(3,4-ethylenedioxythiophene) (PEDOT), poly(hydroxymethyl 3,4-ethylenedioxythiophene) (PEDOT-MeOH), or Prussian blue (PB).
In another embodiment of the disclosure, a material of the metal layer includes platinum (Pt).
In another embodiment of the disclosure, a ratio of an area of the first electrochromic layer to an area of the sensitized light-absorbing layer is between 1 and 4.
Based on the above, in the disclosure, with the specific design of the sensitized light-absorbing layer and the electrochromic layer, the manufacturing processes of the sensitized light-absorbing layer and the electrochromic layer can be separated, so that the energy supply terminal and the electrochromic material in the PECD can be provide on the same photoelectrode. Therefore, the selection of materials can be more diverse, and conductive polymers which are less resistant to high temperature processes can be used as the material of the electrochromic layer, so as to significantly improve the slow response time of using an oxide as the electrochromic material in the conventional art. Moreover, in addition to using metal and similar materials as the counter electrode, a dual-function counter electrode having a high transmittance can also be used to enhance the performance of the PECD, that is, the electrochromic material is used as the counter electrode. In the disclosure, with the operation mechanism of the structure and the diversity of the electrochromic layer material, the response time of the device exhibits a tendency of significant shortening as compared with the conventional PECD. In addition, the disclosure exhibits a high photocoloration efficiency (PhCE), which reduces the energy requirements, and it has been experimentally confirmed that the photoelectrochromic device of the disclosure exhibits a fast response time and can complete coloration and bleaching and achieve balance within seconds.
To make the aforementioned more comprehensible, several embodiments accompanied with drawings are described in detail as follows.
The accompanying drawings in the following embodiments are intended to describe the embodiments of the disclosure more completely, but the disclosure may still be implemented in many different forms and is not limited to the described embodiments. In addition, the relative thickness, distance, and position of each region or film layer may have been reduced or enlarged to make the difference clear, so the sizes in the drawings may not have been drawn to scale. In addition, similar or identical reference numerals are used in the drawings to indicate similar or identical parts or regions.
Referring to
In an embodiment, the material of the first electrochromic layer 106 may include a transition metal oxide, a metal cyanide, an organic small molecule compound, or a conductive polymer. The transition metal oxide may include, but is not limited to: tungsten oxide (WO3), molybdenum trioxide (MoO3), titanium oxide (TiO2), tantalum oxide (Ta2O5), niobium oxide (NbO), nickel oxide (NiO), vanadium oxide (V2O5), chromic oxide (CrO3), cobalt oxide (CoO), iridium oxide (IrO2), or rhodium oxide (Rh2O3). The metal cyanide may include, but is not limited to: Prussian blue (PB), iron cobalt cyanide, ruthenium ferrocyanide, nickel ferrocyanide, and the like. The organic small molecule compound may include, but is not limited to: viologen, methyl viologen, or heptyl viologen. The conductive polymer may include, but is not limited to: polypyrrole (PPy), poly(3-methyl thiophene) (PMeT), polyaniline (PANI), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(hydroxymethyl 3,4-ethylenedioxythiophene) (PEDOT-MeOH), poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT-PSS), poly(2,2-dimethyl-3,4-propylenedioxythiophene) (PProdot-Me2), or poly(2,2-diethyl-3,4-propylenedioxythiophene) (PProdot-Et2). From the viewpoint of shortening the response time, the material of the first electrochromic layer 106 may be poly(3,4-ethylenedioxythiophene) (PEDOT), poly(hydroxymethyl 3,4-ethylenedioxythiophene) (PEDOT-MeOH), or Prussian blue (PB), preferably PEDOT-MeOH. The sensitized light-absorbing layer 108 may include a photosensitized dye layer, such as a TiO2 layer absorbed with a dye. In this embodiment, a distance d between the first electrochromic layer 106 and the sensitized light-absorbing layer 108 may be 0.05 cm or less (see
However, the disclosure is not limited thereto. In another embodiment, the first electrochromic layer 106 and the sensitized light-absorbing layer 108 are in direct contact with each other and do not overlap with each other (see
Referring to
In this embodiment, since the first electrochromic layer 106 and the sensitized light-absorbing layer 108 are separated (not overlapped), there is no need to be concerned about the temperature resistance of the electrochromic material and prevent the cathodic coloring material (first electrochromic layer 106) from being damaged by the high temperature calcination process when manufacturing the sensitized light-absorbing layer 108. Therefore, in addition to the high temperature resistant transition metal oxide, the organic small molecular compound or the conductive polymer which has a short response time may also be used as the electrochromic material. In other words, first, the sensitized light-absorbing layer 108 may be fired and formed at a high temperature on the surface 104a of the first transparent conductive substrate 104, and then the first electrochromic layer 106 may be formed at a lower temperature. Moreover, the second electrochromic layer 112 of the counter electrode plate CE also has the dual functions of simultaneously changing color and catalyzing the negative ions of the electrolytic solution (electrolyte 102). Even if the transition metal oxide is used as the material of the first electrochromic layer 106, since the first electrochromic layer 106 and the sensitized light-absorbing layer 108 do not overlap with each other, the light irradiated to the sensitized light-absorbing layer 108 does not pass through the first electrochromic layer 106, which can increase the light absorption of the sensitized light-absorbing layer 108 and thereby increase the photoelectric conversion efficiency.
The operation mechanism of the photoelectrochromic device 100 will be described below, and an electrolytic solution containing LiI and I2 is used as the electrolyte 102 as an example. First, in the case of open circuit/illumination, the dye molecules (S) in the sensitized light-absorbing layer 108 receive the photon energy and transform from the ground state (S0) to the excited state (S*). The dye in the excited state injects electrons into the semiconductor nanoparticles in the sensitized light-absorbing layer 108, so that the dye molecules are oxidized (S+), the oxidized dye molecules react with the iodide ions (I−) in the electrolyte 102 and return to the ground state, and the iodide ions are oxidized to triiodide ions (I3−). If the first electrochromic layer 106 located next to the sensitized light-absorbing layer 108 is a reduction coloring material, it will receive the electrons from the dye molecules and undergo a reduction reaction. At this time, the lithium ions in the electrolyte 102 play the role of balancing the charge and migrate into the first electrochromic layer 106 to transform it from a bleached state to a colored state. In the case of short circuit/dark, the first electrochromic layer 106 in the colored state is oxidized and bleached by the electrolyte 102 due to the diffusion effect. In addition, with the ability to catalyze I3− reduction, the second electrochromic layer 112 on the CE side accelerates the bleaching process of the first electrochromic layer 106. Analogously, if the first electrochromic layer 106 located next to the sensitized light-absorbing layer 108 is an oxidization coloring material (e.g., using a PB film as the first electrochromic layer and a PEDOT-MeOH film as the second electrochromic layer), the operation of the bleaching process is as follows. In the case of illumination/open circuit (I/OC), the dye molecules (S) in the photoelectrode receive the photon energy and transform from the ground state (S0) to the excited state (S*), and the dye in the excited state injects electrons into the semiconductor nanoparticles, so that the dye molecules are oxidized (S+), the oxidized dye molecules react with I− and return to the ground state, and I− is oxidized to I3−. At this time, the PB in the photoelectrode receives the electrons excited by the dye molecules and undergoes a reduction reaction to bleach, and Li+ is doped on the PB film to balance the charge. At the same time, the PEDOT-MeOH film on the counter electrode is oxidized by I3− in the electrolytic solution and turns into the bleached state, and ClO4− is doped on the PEDOT-MeOH film to balance the charge. The operation of the coloring process is as follows. In the case of illumination/short circuit (I/SC), the dye molecules (S) in the photoelectrode receive the photon energy and transform from the ground state (S0) to the excited state (S*), and the dye in the excited state injects electrons into the semiconductor nanoparticles, so that the dye molecules are oxidized (S+), the oxidized dye molecules react with I− and return to the ground state, and I− is oxidized to I3−. Due to the short circuit, there is no bias between the two electrodes, so that the PB film in the reduced state in the photoelectrode is quickly oxidized by I3− in the electrolytic solution, Li+ migrates out of the PB film to balance the charge, and most of the oxidation reaction of the PB is catalyzed by the PEDOT-MeOH on the counter electrode. At the same time, the electrons generated by the photoelectrode are transferred to the counter electrode via an external circuit, so that the PEDOT-MeOH undergoes a reduction reaction and is colored. At this time, ClO4− migrates out of the PEDOT-MeOH film to balance the charge.
Referring to
Experiments will be described below to verify the effect of the disclosure, but the disclosure is not limited to the following content.
1. Preparation of Photoelectrode (WE)
1-1. Preparation of Sensitized Light-Absorbing Layer
The sensitized light-absorbing layer included three TiO2 layers in total, including a contact layer, a transmission layer, and a scattering layer. The contact layer TiO2 was prepared by mixing titanium tetraisopropoxide (TTIP) and 2-methoxyethanol at a weight ratio of 1:3. The transmission layer TiO2 was purchased from Solaronix. The synthesis steps of the scattering layer TiO2 are as follows. First, TTIP (0.5 M) and a nitric acid aqueous solution (0.1 M) were mixed and uniformly stirred at 88° C. for 8 hours, and then heated to 240° C. for 12 hours in a hydrothermal kettle. After the reaction was completed, the TiO2 slurry in the hydrothermal kettle contained 8% by weight of TiO2 nanoparticles. In the previously synthesized TiO2 slurry, 25% by weight of polyethylene glycol (PEG) (relative to the TiO2 nanoparticles) and 100% by weight of model ST-41 anatase TiO2 (relative to the TiO2 nanoparticles) of Ishihara Sangyo Kaisha ltd were added to synthesize a TiO2 colloid for the scattering layer.
After preparing the above three-layer TiO2 solution and colloid, the contact layer TiO2 was coated on the surface of a 2.0 cm×4.0 cm FTO conductive glass by spin coating at a parameter of 3000 rpm for 30 seconds, and the coating area was 1.0 cm×2.0 cm. The transmission layer TiO2 and the scattering layer TiO2 were both coated by a doctor blade, and the coating area was 1.0 cm×0.25 cm. The coating sequence was the contact layer, the transmission layer, and the scattering layer, and after coating, each layer needed to be sintered to 500° C. for 30 minutes. Finally, the sintered TiO2 electrode was soaked in N719 dye for 24 hours to complete the preparation of the sensitized light-absorbing layer.
1-2. Preparation of First Electrochromic Layer
EDOT-MeOH (0.01 M) and LiClO4 (0.1 M) were dissolved in an acetonitrile (ACN) solvent to form a plating solution.
A working area of 1.0 cm×1.0 cm was enclosed by an epoxy tape at a distance of 0.05 cm from the edge of the sensitized light-absorbing layer, and then the EDOT-MeOH monomer in the above plating solution was polymerized on the surface of the FTO conductive glass at a constant potential by a constant potential deposition method. The parameter of the constant potential method was 1.2 V and the power was limited to 13 mC. Finally, the prepared PEDOT-MeOH (first electrochromic layer) was rinsed with ACN to wash away the remaining plating solution on the surface, and the surface was blown and dried with nitrogen.
2. Preparation of Counter Electrode Plate (CE)
EDOT-MeOH (0.01 M) and LiClO4 (0.1 M) were dissolved in an acetonitrile (ACN) solvent to form a plating solution.
A working area of 1 cm×1.3 cm was enclosed by an epoxy tape on the surface of an ITO conductive glass of 2.0 cm×4.0 cm, and then the EDOT-MeOH monomer in the above plating solution was polymerized on the surface of the ITO conductive glass at a constant potential by a constant potential deposition method. The parameter of the constant potential method was 1.2 V and the power was limited to 13 mC. Finally, the prepared PEDOT-MeOH (second electrochromic layer) was rinsed with ACN to wash away the remaining plating solution on the surface, and the surface was blown and dried with nitrogen.
3. Packaging of Photoelectrochromic Device
The periphery of the counter electrode plate (CE) was encapsulated with Surlyn® as the thickness control layer and the packaging material, then the photoelectrode (WE) and the counter electrode plate (CE) were combined by a binder clip, and finally the Surlyn® between the two electrode plates was melted by hot pressing. Then, the required electrolytic solution was injected into the corner holes with a 5 mL syringe, and a transparent tape was attached thereto to complete the package. The formulation of the electrolytic solution was respectively a PC solvent containing LiI (0.5 M) and I2 (0.001 M) or a PC solvent containing LiI (0.5 M) and I2 (0.005 M).
1. Preparation of Photoelectrode (WE) (Without First Electrochromic Layer)
1-1. Preparation of Sensitized Light-Absorbing Layer: Same as Preparative Example 1.
2. Preparation of Counter Electrode Plate (CE): Same as Preparative Example 1.
3. Packaging of Photoelectrochromic Device: Same as Preparative Example 1.
1. Preparation of Photoelectrode (WE)
1-1. Preparation of Sensitized Light-Absorbing Layer: Same as Preparative Example 1.
1-2. Synthesis of Nano-Prussian Blue (PB) Particles
3.23 g of Fe(NO3)3.9H2O and 2.90 g of Na4Fe(CN)6.10H2O were mixed in 45 mL of pure water and shaken well. The mixed solution was centrifuged in a centrifuge at 4000 rpm for 30 minutes, the centrifuged precipitate was centrifuged with pure water at 4000 rpm for 5 minutes six times, and 0.542 g of Na4Fe(CN)6.10H2O and 10 mL of pure water were added to the centrifuged precipitate and stirred for one week. The stirred solution was centrifuged at 3000 rpm for 15 minutes, then the centrifuged clarified liquid was subjected to a rotary concentration process to obtain the PB powder, and finally the powder was dried under vacuum for one day.
1-3. Preparation of First Electrochromic Layer
Before the preparation, an ITO glass was placed in an ozone cleaner for cleaning for 30 minutes to increase the hydrophilicity of the surface. PB and pure water at 100 mg/mL were used as the plating solution, and 40 μL of the solution was evenly dripped on the surfaces of the cleaned ITO glass and the photoelectrode by spin coating at 3000 rpm for 30 seconds. Then, a cotton swab dipped in pure water was used to wipe a 1.0 cm×1.0 cm PB area on the electrode plate after the spin coating. Finally, it was placed on a hot plate at 80° C. for 30 minutes to dry to complete the preparation of the photoelectrode (WE).
2. Preparation of Counter Electrode Plate (CE): Same as Preparative Example 1.
3. Packaging of Photoelectrochromic Device: Same as Preparative Example 1.
1. Preparation of Photoelectrode (WE): Same as Preparative Example 1.
2. Preparation of Counter Electrode Plate (CE)
First, nano-Prussian blue (PB) particles were synthesized by the method of Preparative Example 2.
Then, an ITO glass was placed in an ozone cleaner for cleaning for 30 minutes to increase the hydrophilicity of the surface. PB and pure water at 100 mg/mL were used as the plating solution, and 40 μL of the solution was dripped evenly on the surface of the cleaned ITO glass by spin coating at 3000 rpm for 30 seconds. Then, a cotton swab dipped in pure water was used to wipe a 1.0 cm×1.3 cm PB area on the electrode plate after the spin coating. Finally, it was placed on a hot plate at 80° C. for 30 minutes to dry to complete the preparation of the counter electrode plate (CE).
3. Packaging of Photoelectrochromic Device: Same as Preparative Example 1.
[Response Time]
The packaged photoelectrochromic device (PECD) was fixed on the spectrophotometer platform, and the light source in the spectrophotometer was applied to the first electrochromic layer on the photoelectrode to detect the coloring/bleaching response time of the electrochromic material, and the spectrophotometer was connected with a computer to record the optical performance changes of the PECD.
The sun simulator was set on the front-lateral side of the spectrophotometer platform to irradiate to the sensitized light-absorbing layer (TiO2/dye layer) in the photoelectrode to drive the dye to excite electrons, so that the electrochromic material underwent a bleaching reaction. The device is as shown in
The device of
[Photocoloration Efficiency]
The device in
In summary of the above, since the photoelectrode and the electrochromic layer of the disclosure can be manufactured separately, the selection of the electrochromic material can be more diverse, so as to significantly improve the slow response time of using an oxide as the electrochromic material in the conventional art. Moreover, in addition to using metal and similar materials as the counter electrode, a dual-function counter electrode having a high transmittance can also be used to enhance the performance of the PECD, so that the disclosure has a high photocoloration efficiency (PhCE) and reduced energy requirement.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure covers modifications and variations provided that they fall within the scope of the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 109139286 | Nov 2020 | TW | national |
