Voltage-dependent photocurrent transients of PTB7:PC70BM solar cells: Experiment and numerical simulation
Voltage-dependent photocurrent transients of PTB7:PC70BM solar cells: Experiment and numerical simulation
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DOI：
10.1063/1.4813612
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发表时间：
2013-07-21
影响因子：
3.2
通讯作者：
McNeill, Christopher R.
中科院分区：
文献类型：
--
作者：
Li, Zhe;Lakhwani, Girish;McNeill, Christopher R.
本文报道了以聚合物PTB 7和富勒烯受体PC 70 BM的共混物为基础的高效聚合物/富勒烯太阳能电池的瞬态光电流测量结果。特别是，我们研究的光强度依赖性和电压依赖性的开启和关闭的光电流动态的设备响应于200 μ s的平方光脉冲。在短路时，观察到的开启和关闭动力学的细微变化与电荷密度依赖的传输现象相一致。当工作电压从短路移动到开路时，我们观察到在器件稳定到稳态之前的开启后几微秒出现初始瞬态光电流峰值。此外，我们只观察到一个弱的工作电压上的电荷提取动力学的依赖性，随着工作电压从短路到开路移动的电荷提取量单调下降。这一系列的功能解释的帮助下，在电荷捕获的数值模拟，增加陷阱辅助复合更接近开路。还比较了使用和不使用溶剂添加剂二碘辛烷制造的器件的操作。与不使用溶剂添加剂制造的器件相比，使用溶剂添加剂制造的优化器件的电荷捕获特征减少。因此，在该系统中使用溶剂添加剂二碘辛烷对于最小化阱辅助重组是重要的。(C)2013 AIP Publishing LLC.
Transient photocurrent measurements on efficient polymer/fullerene solar cells based on a blend of the donor polymer PTB7 with the fullerene acceptor PC70BM are reported. In particular, we examine the light intensity dependence and voltage dependence of the turn-on and turn-off photocurrent dynamics of devices in response to a 200 mu s square light pulse. At short circuit, subtle changes in the turn-on and turn-off dynamics are observed consistent with charge-density-dependent transport phenomena. As the working voltage is moved from short circuit to open circuit, we observe the appearance of an initial transient photocurrent peak a few microseconds after turn-on before the device settles to steady state. Furthermore, we observe only a weak dependence of the charge extraction dynamics on the working voltage, with the amount of charge extracted monotonically decreasing as the working voltage is moved from short circuit to open circuit. This collection of features is interpreted with the aid of numerical simulations in terms of charge trapping, with increased trap-assisted recombination closer to open circuit. The operation of devices fabricated with and without the solvent additive di-iodooctane is also compared. Charge trapping features are reduced for optimized devices fabricated with the solvent additive compared to devices fabricated without. The use of the solvent additive di-iodooctane in this system is therefore important in minimizing trap-assisted recombination. (C) 2013 AIP Publishing LLC.