聚合溶液pH值对染料敏化太阳电池中聚吡咯对电极结构和性能的影响

Influence of pH Values on the Structure and Performance of a Polypyrrole Counter Electrode for Dye-Sensitized Solar Cells

电化学合成聚吡咯(PPy)时,聚合电解液的pH值对PPy薄膜的形貌和性质有较大的影响,进而影响PPy薄膜对I-/I3-的电催化活性以及基于PPy对电极(CE)的染料敏化太阳电池(DSSCs)的光电转换性能.本文采用电化学恒电位方法,在掺杂氟的SnO2(FTO)导电玻璃上合成出了对甲苯磺酸根离子掺杂的聚吡咯(PPyTsO)电极,并将其作为DSSCs的对电极.通过改变吡咯聚合时聚合电解液的pH值,借助扫描电镜(SEM)、紫外-可见(UV-Vis)吸收光谱、X-射线光电子能谱(XPS)和循环伏安(CV)等表征技术,详细探讨了聚合溶液pH值对PPy CE形貌、结构及其对I-/I3-的电催化性能的影响.研究发现在pH 2.0下合成的聚吡咯对阴离子掺杂率最高且链共轭性最佳,具有对I-/I3-氧化还原介质最强的催化能力,基于此PPy CE的电池光电转化效率也最高.pH值太大或太小都不利于生成具有高掺杂率和高催化活性的PPy电极,组装成DSSCs后的光电转换效率也较低.

The pH of the solution used to produce an electro-polymerized polypyrrole （PPy） film has a significant impact on the morphology and properties of the resulting film and, by extension, on the electrocatalytic activity of the film for the l^-/l3^- redox reaction. Accordingly, the performance of dyesensitized solar cells （DSSCs） based on PPy counter electrodes （CEs） is affected by solution pH. In this study, p-toluene sulfonate ion-doped PPy （PPy-TsO） CEs on fluorinedoped tin oxide （FTO） glass substrates were fabricated using an electrochemical method under a constant bias in solutions with various pH values. The effect of the pH of the synthetic solution on the morphology, structure, and electrocatalytic activity during the l^-/l3^- redox reaction of the obtained PPy CEs was thoroughly investigated by scanning electron microscopy （SEM）, UV-Vis absorption spectroscopy, X-ray photoelectron spectroscopy （XPS）, and cyclic voltammetry （CV）. A pH value of 2.0 was found to represent the optimal value, since the PPy-TsO film produced at this pH exhibited the highest degree of doping, the longest conjugation length, and the highest catalytic activity. When working as the CE of a DSSC, this film also showed the highest power conversion efficiency. Films synthesized at pH values either above or below 2.0 exhibited inferior properties and lower performance when in DSSCs.