摘要/Abstract

本工作主要围绕PEDOT的合成及其在固态染料敏化太阳能电池对电极中的应用开展研究，重点研究了循环伏安法电化学沉积过程中循环次数（10~50次）对PEDOT薄膜的形貌、厚度及光学性质的影响.通过红外光谱、SEM、紫外-可见吸收光谱表征了PEDOT的结构、形貌及光性质；通过J-V、动态调制光电流谱（IMPS）/光电压谱（IMVS）以及Tafel测试表征了基于PEDOT透明对电极染料敏化太阳能电池的光电化学性能.结果表明：采用循环伏安法电沉积合成PEDOT制备固态染料敏化太阳能电池对电极时，CV循环30~40次之间时可以获得最佳的光电性能，固态器件的光电转换效率为5.34%，这是因为在该条件下所制备的PEDOT具有均匀致密的表面、较好的光学性质以及较高的光电催化性能（J₀=2.51×10^-3 A·cm^-2），使得器件可以获得较大的扩散系数（D_n=28.80 μm²·ms^-1）和载流子扩散长度（L=21.41 μm），有利于电荷的传输.当CV循环次数大于40次时，PEDOT薄膜会在掺氟的SnO₂透明导电玻璃（FTO）表面发生溶解、脱附，从而使得其光电催化性能下降.在双面光照条件下，以电沉积PEDOT作为透明对电极的器件光电性能提升了20%左右.
关键词: 固态染料敏化太阳能电池, PEDOT, 透明对电极, 导电聚合物, 循环伏安法
In this paper, the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) by cyclic voltammetry (CV) electrochemical deposition and its application in the counter electrode of solid-state dye-sensitized solar cells were studied. The influence of cycle times (10~50 times) on the morphology, thickness and optical properties of PEDOT films were explored by Fourier transform infrared spectroscopy (FTIR), atomic force microscope (AFM), scanning electron microscope (SEM) and ultraviolet-visible spectroscopy (UV-Vis). The photoelectrochemical properties of solid-state dye-sensitized solar cells based on PEDOT transparent counter electrode were characterized by J-V, electrochemical impedance spectroscopy (EIS), intensity modulated photocurrent spectrum/photovoltage spectrum (IMPS/VS) and Tafel analysis. The results showed that an un-uniform film with the thickness of 0.5 μm and light transmittance of 80% was formed when CV cycle times was 10, where the PEDOT film was not completely covered on the substrate. When the CV cycles reached 30~40, a uniform and dense transparent film was obtained and the highest photoelectric conversion efficiency of the corresponding solid-state dye-sensitized solar cells reached 5.34%. This is because uniform and dense surface, good optical properties and high photo-electric catalysis properties (J₀=2.51×10^-3 A·cm^-2) for I₃^- in the electrolyte, made the device obtain larger diffusion coefficient (D_n=28.80 μm²·ms^-1) and carrier diffusion length (L=21.41 μm), which were favorable for charge transfer. When the number of CV cycles was further increased to 50 times, showing greater roughness, the PEDOT film was no longer growing uniformly. The PEDOT film deposited on the FTO surface underwent some dissolution and desorption, the PEDOT film became uneven, and the catalytic activity of PEDOT electrode to I₃^- in electrolyte was reduced. The device with PEDOT transparent counter electrode film deposited by cyclic voltammetry could also achieve double-side illumination with good catalytic activity to the electrolyte. Under the condition of double-side illumination, the photoelectric performance of the device using electrodeposited PEDOT as transparent counter electrode was improved by about 20%. The improvement of the photoelectric performance of the device is mainly due to the increase in the absorption of photons by the double-sided illumination.
Key words: solid-state dye-sensitized solar cells, PEDOT, transparent counter electrode, conductive polymers, cyclic voltammetry method


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