Interpreting the Density of States Extracted from Organic Solar Cells Using Transient Photocurrent Measurements
Interpreting the Density of States Extracted from Organic Solar Cells Using Transient Photocurrent Measurements
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DOI：
10.1021/jp4010828
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发表时间：
2013-06
影响因子：
3.7
通讯作者：
R. MacKenzie;C. Shuttle;George F. A. Dibb;N. Treat;E. Hauff;M. Robb;C. Hawker;M. Chabinyc;J. Nelson
中科院分区：
文献类型：
--
作者：
R. MacKenzie;C. Shuttle;George F. A. Dibb;N. Treat;E. Hauff;M. Robb;C. Hawker;M. Chabinyc;J. Nelson
有机光伏(OPV)器件中捕获载流子态(DO)的能量分布是控制载流子迁移率和复合速率的关键参数，最终会限制器件的效率。最近的研究试图使用从飞行时间(ToF)方法改编而来的瞬时光电流方法来测量工作的OPV设备的DO，该方法最初是为了测量厚单极设备的迁移率而开发的。虽然使用简单的光电手段从OPV设备中提取DO的方法将是有价值的，但由于双极有机太阳能电池中同时存在电子和空穴，分析变得复杂。这两种载体物种的存在导致了提取的DO的失真，这是由于(A)从光电流瞬变中移除载流子的复合损失，从而改变了其形状，以及(B)在任何测量中都同时观察到LUMO和HOMO DO特征。在本文中，我们使用一个详细的器件模型来确定从双极器件的暂态光电流中安全地提取DO的条件。我们证明了在反向偏置条件下，从工作的OPV设备中提取未失真的DO是可能的。我们应用我们的方法估计了一种新型的低禁带、基于二酮基吡咯的聚合物与(6，6)-苯基-C71-丁酸甲酯(PC71BM)混合制成的体相异质结太阳能电池中的DO，以及由聚(3-己基噻吩基)：苯基-C61-丁酸甲酯(P3HT：PCBM)制成的太阳能电池在不同温度下的退火态。
The energetic distribution of trapped carrier states (DoS) in organic photovoltaic (OPV) devices is a key device parameter which controls carrier mobility and the recombination rate; as such, it can ultimately limit device efficiency. Recent studies have attempted to measure the DoS from working OPV devices using transient photocurrent methods adapted from the time-of-flight (ToF) method originally developed to measure mobility in thick unipolar devices. While a method to extract the DoS from OPV devices using a simple optoelectronic means would be valuable, analysis is complicated by the presence of both electrons and holes in the bipolar organic solar cells. The presence of both carrier species leads to distortion of the extracted DoS due to (a) recombination losses removing carriers from the photocurrent transient thus changing its shape and (b) both LUMO and HOMO DoS features being observed simultaneously in any measurement. In this paper we use a detailed device model to determine the conditions under which the DoS can safely be extracted from the transient photocurrent from bipolar devices. We show that under conditions of reverse bias it is possible to extract the undistorted DoS from a working OPV device. We apply our method to estimate the DoS in a bulk heterojunction solar cell made of a novel low band gap, diketopyrrolopyrrole-based polymer blended with (6,6)-phenyl-C71-butyric acid methyl ester (PC71BM) and solar cells made of poly(3 hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) annealed over a range of temperatures.