二极管特性简化模型在染料敏化太阳能电池电流-电压曲线拟合及在光电特性参数评估中的应用

利用瞬态光电导技术研究了在一个大的偏压范围内染料敏化太阳能电池(DSSC)中的电荷收集和电荷复合过程的动力学. 结果表明, 在不同的电压下电荷收集速率远快于电荷复合速率, 用以解释电荷的收集效率几乎不变. 基于这个结果, 简化了DSSC二极管特性模型, 从而实现了对电流-电压(I-V)曲线的直接拟合. 利用这一模型拟合的结果提取出一系列与工作条件下DSSC光电转化过程相关的参数, 可以用以描述包括电荷生成、电荷收集和复合以及DSSC器件的整流特性等关键性质. 将这一拟合方法应用于不同叔丁基吡啶(TBP)浓度电解液的电池, 获得的结果表明, 不同TBP浓度可以导致电荷复合速率有较大的差别, 但对电荷的收集速率影响甚小, 这与I-V曲线拟合的结果非常吻合. 同时研究证明TBP浓度对电池的理想因子(m)的影响较为明显,即高浓度TBP的DSSC对应大的m值以及较慢的电荷复合速率.

Application of a Simplified Diode Characteristic Model in Current-Voltage Curve Fitting and Evaluation of Photoelectric Parameters within Dye-Sensitized Solar Cell

In the present work, we investigated the dynamics of charge collection and recombination in dyesensitized solar cells (DSSCs) spanning a large region of bias voltages using transient photoconductivity. The rate of charge collection was much faster than that of charge recombination at varied voltages, which was responsible for the nearly uniform charge collection efficiency. Based on this result, we simplified the diode characteristic model, which allowed us to directly fit the current-voltage (I-V) curve. A series of parameters related to the photo-to-electric processes in working DSSCs could be extracted from the proposed model, which could be used to evaluate the processes of charge generation, transport, and recombination in DSSCs, as well as the rectification of DSSC devices. We applied the fitting method to DSSCs with different 4-tert-butyl pyridine (TBP) concentrations of electrolyte. It was found that the rate of charge recombination significantly differed while that of charge collection was rather constant under different TBP concentrations, which was in good agreement with the results of I-V curve fitting. In addition, this research shows that the change of TBP concentration significantly affects the ideality factor (m) of DSSC devices.