Centre for Plastic Electronics, Department of Chemistry, Imperial College London, South Kensington, SW7 2AZ, United Kingdom.
Proc Natl Acad Sci U S A. 2010 Sep 21;107(38):16448-52. doi: 10.1073/pnas.1004363107. Epub 2010 Sep 7.
A key challenge for organic electronics research is to develop device models that correctly account for the structural and energetic disorder typically present in such materials. In this paper we report an approach to analyze the electrical performance of an organic electronic device based upon charge extraction measurements of charge densities and transient optoelectronic measurements of charge carrier dynamics. This approach is applied to a poly(3-hexyl thiophene) (P3HT)/6,6 phenyl C61 butyric acid methyl ester (PCBM) blend photovoltaic device. These measurements are employed to determine the empirical rate law for bimolecular recombination losses, with the energetic disorder present in the materials being accounted for by a charge-density-dependent recombination coefficient. This rate law is then employed to simulate the current/voltage curve. This simulation assumes the only mechanism for the loss of photogenerated charges is bimolecular recombination and employs no fitting parameters. Remarkably the simulation is in good agreement with the experimental current/voltage data over a wide range of operating conditions of the solar cell. We thus demonstrate that the primary determinant of both the open-circuit voltage and fill factor of P3HT:PCBM devices is bimolecular recombination. We go on to discuss the applicability of this analysis approach to other materials systems, and particularly to emphasize the effectiveness of this approach where the presence of disorder complicates the implementation of more conventional, voltage-based analyses such as the Shockley diode equation.
有机电子学研究的一个关键挑战是开发能够正确考虑到此类材料中通常存在的结构和能量无序的器件模型。在本文中，我们报告了一种基于电荷密度的电荷提取测量和电荷载流子动力学的瞬态光电测量来分析有机电子器件的电性能的方法。该方法应用于聚(3-己基噻吩)(P3HT)/6,6-苯基 C61 丁酸甲酯(PCBM) 混合光伏器件。这些测量用于确定双分子复合损耗的经验速率定律，其中材料中的能量无序通过与电荷密度相关的复合系数来考虑。然后，该速率定律用于模拟电流-电压曲线。该模拟假设光生电荷损失的唯一机制是双分子复合，并且不使用拟合参数。值得注意的是，该模拟在太阳能电池的广泛工作条件下与实验电流-电压数据非常吻合。因此，我们证明了 P3HT:PCBM 器件的开路电压和填充因子的主要决定因素是双分子复合。我们接着讨论了这种分析方法对其他材料系统的适用性，并特别强调了在无序存在使更传统的基于电压的分析（如肖克利二极管方程）变得复杂的情况下，这种方法的有效性。
