Overcoming the Limitations of Transient Photovoltage Measurements for Studying Recombination in Organic Solar Cells
Overcoming the Limitations of Transient Photovoltage Measurements for Studying Recombination in Organic Solar Cells
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DOI：
10.1002/solr.201900581
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发表时间：
2020-03-20
期刊：
影响因子：
7.9
通讯作者：
Nelson, Jenny
中科院分区：
文献类型：
--
作者：
Azzouzi, Mohammed;Calado, Philip;Nelson, Jenny
瞬态光电压（TPV）测量经常用于研究薄膜太阳能电池中的复合过程，其通过探测小的光致电压扰动的衰减来推断器件在开路时的电荷载流子动力学。然而，这种方法来探测有机半导体的有效性最近受到怀疑，由于在相同的系统和不切实际的反应级数值的报告的载流子寿命值的大的差异。在此，TPV提取可靠的电荷载流子寿命在薄膜太阳能电池的有效性进行了探讨，通过使用时间依赖性漂移扩散模拟和测量。结果发现，在低迁移率材料中，TPV主要作为探针的电荷载流子的再分布在散装，而不是散装复合动力学和提取的时间常数是高度依赖于迁移率。为了解决这个缺点，瞬态光电荷，一种新的技术来测量光电压衰减过程中的载流子密度，被引入和应用于研究一系列（富勒烯和非富勒烯）有机太阳能电池系统中的复合动力学。它表明，使用这种技术的有源层中的载流子复合寿命更准确地确定。
Transient photovoltage (TPV) measurements are frequently used to study recombination processes in thin-film solar cells by probing the decay of a small optically induced voltage perturbation to infer the charge carrier dynamics of devices at open circuit. However, the validity of this method to probe organic semiconductors has recently come into doubt due to large discrepancies in the reported carrier lifetime values for the same systems and the reporting of unrealistic reaction order values. Herein, the validity of TPV to extract reliable charge carrier lifetimes in thin-film solar cells is explored through the use of time-dependent drift-diffusion simulations and measurements. It is found that in low-mobility materials, TPV serves primarily as a probe of charge carrier redistribution in the bulk rather than bulk recombination dynamics and that the extracted time constant is highly mobility dependent. To address this shortcoming, transient photocharge, a new technique to measure the charge carrier density during photovoltage decay, is introduced and applied to study the recombination dynamics in a series of (fullerene and nonfullerene) organic solar cell systems. It is shown that using this technique the charge carrier recombination lifetime in the active layer is more accurately determined.