Organic solar cells (OSCs) utilizing π-conjugated polymers have attracted widespread interest over the past three decades because of their potential advantages, including low weight, thin film flexibility, and low-cost manufacturing. However, their power conversion efficiency (PCE) has been far below that of inorganic analogs. Geminate recombination of charge transfer excitons is a major loss process in OSCs. This paper reviews our recent progress in using transient absorption spectroscopy to understand geminate recombination in bulk heterojunction OSCs, including the impact of polymer crystallinity on charge generation and dissociation mechanisms in nonfullerene acceptor-based OSCs. The first example of a high PCE with a small photon energy loss is also presented. The importance of delocalization of the charge wave function to suppress geminate recombination is highlighted by this focus review. When light is shined on semiconducting polymers, singlet excitons are promptly generated in organic solar cells. At a donor–acceptor heterojunction, excitons separate into holes on the donor and electrons on the acceptor as a result of the energetic offset of the molecular orbital. If the electron and hole separate further, they become free from Coulombic attraction and hence survive up to nano- or microseconds, long enough to be transported to each electrode. Otherwise, the geminate electron–hole pairs are likely to recombine to the ground state.

中文翻译：

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离域促进有机太阳能电池中的电荷分离

在过去的 30 年里，利用 π 共轭聚合物的有机太阳能电池 (OSC) 因其潜在的优势而引起了广泛的兴趣，包括重量轻、薄膜柔韧性好和制造成本低。然而，它们的功率转换效率 (PCE) 远低于无机类似物。电荷转移激子的双子复合是 OSC 中的一个主要损失过程。本文回顾了我们最近在使用瞬态吸收光谱来了解本体异质结 OSC 中的成对复合方面的最新进展，包括聚合物结晶度对基于非富勒烯受体的 OSC 中电荷生成和解离机制的影响。还介绍了具有小光子能量损失的高 PCE 的第一个示例。这篇焦点评论强调了电荷波函数的离域化对抑制成对重组的重要性。当光线照射在半导体聚合物上时，有机太阳能电池中会迅速产生单线态激子。在供体-受体异质结处，由于分子轨道的能量偏移，激子分离成供体上的空穴和受体上的电子。如果电子和空穴进一步分离，它们将不受库仑引力的影响，因此可以存活达纳秒或微秒，足够长的时间被传输到每个电极。否则，成对的电子-空穴对很可能重新结合到基态。在供体-受体异质结处，由于分子轨道的能量偏移，激子分离成供体上的空穴和受体上的电子。如果电子和空穴进一步分离，它们将不受库仑引力的影响，因此可以存活达纳秒或微秒，足够长的时间被传输到每个电极。否则，成对的电子-空穴对很可能重新结合到基态。在供体-受体异质结处，由于分子轨道的能量偏移，激子分离成供体上的空穴和受体上的电子。如果电子和空穴进一步分离，它们将不受库仑引力的影响，因此可以存活达纳秒或微秒，足够长的时间被传输到每个电极。否则，成对的电子-空穴对很可能重新结合到基态。