Light absorption generates strongly bound excitons in organic solar cells (OSCs). To obtain efficient charge generation, a large driving force is required, which causes a large energy loss (Eloss) and severely hinders the improvement in the power conversion efficiencies (PCEs) of OSCs. Recently, the development of non-fullerene OSCs has seen great success, and the resulting OSCs can yield highly efficient charge generation with a negligible driving force, which raises a fundamental question about how the excitons split into free charges. From a chemical structure perspective, the molecular electrostatic potential differences between donors and acceptors may play a critical role in facilitating charge separation. Although the Eloss caused by charge generation has been suppressed, charge recombination, particularly via non-radiative pathways, severely limits further improvements in the PCEs. In OSCs with negligible driving forces, the lowest excited state, a hybrid local exciton-charge transfer state, is believed to have a strong association with the non-radiative Eloss. This review discusses the efficient charge generation at low Eloss values in highly efficient OSCs and highlights the issues that should be tackled to further improve the PCEs to new levels (~ 20%).

中文翻译：

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在有机太阳能电池中以低能量损失有效产生电荷：一个关键问题回顾

光吸收在有机太阳能电池 (OSC) 中产生强束缚激子。为了获得有效的电荷产生，需要很大的驱动力，这会导致较大的能量损失（Eloss），严重阻碍了OSCs功率转换效率（PCE）的提高。最近，非富勒烯 OSCs 的开发取得了巨大成功，由此产生的 OSCs 可以在驱动力可忽略不计的情况下产生高效的电荷，这提出了激子如何分裂成自由电荷的基本问题。从化学结构的角度来看，供体和受体之间的分子静电势差可能在促进电荷分离方面发挥关键作用。尽管由电荷产生引起的 Eloss 已被抑制，但电荷重组，特别是通过非辐射途径，严重限制了 PCE 的进一步改进。在驱动力可忽略不计的 OSC 中，最低激发态，混合局部激子 - 电荷转移态，被认为与非辐射 Eloss 有很强的关联。本综述讨论了高效 OSC 在低 Eloss 值下的有效电荷生成，并强调了应解决的问题，以进一步将 PCE 提高到新水平（~ 20%）。