The time-delayed collection field (TDCF) technique is a popular method to quantify the field and temperature dependences of free charge generation in organic solar cells. Because the method relies on the extraction of photogenerated charge carriers, bimolecular recombination not only between the photogenerated carriers but also between the photogenerated and dark-injected carriers affects its accuracy, particularly at forward bias. In this work, drift–diffusion simulations are employed to quantify the recombination losses in conventional and modified TDCF measurements, where the latter technique intends to reduce the impact of dark injection. It is shown that parameters such as the generation profile, carrier mobilities, and effective density of states affect the recombination losses in both measurements. Importantly, modified TDCF enables to reduce the recombination losses at forward bias, especially beyond the open-circuit voltage. However, conventional TDCF is preferable for studies at reverse bias due to a better depletion of the active layer prior to the emergence of the photogenerated carriers. Measurements on a ZR1:Y6 blend with fast recombination are in good agreement with the simulation results. This work shows that artifacts in TDCF measurements related to non-geminate recombination can be accounted for and minimized through an informed choice of the experimental conditions.

中文翻译：

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关于双分子重组对延时收集场测量的影响以及如何最小化其影响

延时收集场 (TDCF) 技术是量化有机太阳能电池中自由电荷产生的场和温度依赖性的流行方法。由于该方法依赖于光生载流子的提取，因此不仅光生载流子之间的双分子复合，而且光生载流子与暗注入载流子之间的双分子复合也会影响其准确性，特别是在正向偏压下。在这项工作中，采用漂移扩散模拟来量化传统和改进的 TDCF 测量中的复合损失，其中后一种技术旨在减少暗注入的影响。结果表明，生成分布、载流子迁移率和有效态密度等参数会影响两种测量中的复合损耗。重要的是，改进的 TDCF 能够减少正向偏置时的复合损耗，尤其是超出开路电压时。然而，由于在光生载流子出现之前有源层更好地耗尽，因此传统的 TDCF 更适合反向偏压的研究。对具有快速重组的 ZR1:Y6 共混物的测量与模拟结果非常吻合。这项工作表明，通过明智地选择实验条件，可以解释并最小化与非成对重组相关的 TDCF 测量中的伪影。