聚合时间对染料敏化太阳能电池中聚苯胺对电极结构和性能的影响

采用恒电压方法, 以掺杂氟的SnO₂ (FTO)导电玻璃为基底, 采用不同的聚合时间制备SO₄^2?掺杂的聚苯胺对电极(PANI CEs). 利用扫描电子显微镜(SEM)、紫外-可见(UV-Vis)吸收光谱、循环伏安法(CV)和电化学阻抗谱(EIS)等技术详细研究了聚合时间对PANI CEs的表面形貌、结构(如掺杂度、共轭性、氧化态等)和对I^?/I^3?的催化活性的影响. SEM结果表明PANI在FTO上的生长分两个阶段. 适当增加聚合时间可以增加PANI CEs的比表面积, 为催化I^?/I^3?反应提供更多的活性位点, 同时聚苯胺链的共轭性、半氧化态聚苯胺(EB)结构的含量和对阴离子SO₄^2?的掺杂度会随着增加, 进而PANI 的导电率也逐渐增大. 然而, 聚合时间过长会引起薄膜厚度的增加和氧化结构的过多, 使PANI CEs的导电率降低, 电子在PANI 薄膜中的传输阻抗增加, 进而影响其对I^?/I^3?的催化性能. 聚合时间为300 s 时制备出的PANI 薄膜作为染料敏化太阳能电池(DSSCs)对电极和以D149 为染料时, 获得的最高电池光电转换效率为5.30%, 可达到基于Pt 对电极电池效率的88%. 因此, 通过电化学方法制备的PANI CEs有望代替贵金属Pt CEs用于DSSCs中.

Influences of Polymerization Time on Structure and Properties of Polyaniline Counter Electrodes in Dye-Sensitized Solar Cells

SO₄^2? doped polyaniline (PANI) counter electrodes (CEs) on fluorine-doped tin oxide (FTO) glass substrates were fabricated, using electrochemical method under constant bias for different polymerization time. The effect of polymerization time on surface morphology, structure (such as doping level, conjugation and oxidization state), and electrocatalytic activity for I^?/I₃^? redox reaction of the obtained PANI CEs was investigated by scanning electron microscopy (SEM), UV-Vis absorption spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). SEM results indicated that the growth of PANI films on FTO substrate occurred in two phases. Properly increasing polymerization time could increase the specific surface area of PANI CEs, affording more electrocatalytic sites for the I^?/I₃^? redox reaction. Meanwhile, the conductivity of the PANI CEs increased gradually because of enhanced conjugation, emeraldine base (EB) structure, and SO₄^2? doping degree. If the polymerization time was too long, however, the CE conductivity would decrease due to the formation of a thick film and superabundance of oxidized structure, resulting in an increase in the electron transfer resistance and decrease in the electrocatalytic activity of PANI CEs for I^?/I₃^? redox reaction. Dye-sensitized solar cells (DSSCs) based on PANI CEs with a polymerization time of 300 s and D149 dye showed the best photovoltaic performance, with a solar-to-energy conversion efficiency of 5.30%. This result is approximately 88% of the efficiency of Pt CE based-solar cells, suggesting that PANI CEs polymerized with electrochemical method may replace Pt CEs in DSSCs.