ConspectusOver the past few years, the development of new materials has contributed to rapid increases in the power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells to over 17%, showing great potential for the commercialization of this technology in the near future. At this stage, designing new materials with superior performance and low cost simultaneously is of crucial importance. Chlorinated materials are emerging as new stars with very high PCEs, creating a molecular design trend to replace the most popular fluorinated materials. For example, by using chlorinated non-fullerene acceptors, we recently got a record PCE of 17% for single-junction OPV cells. Firmly based on recent advances, herein we focus on the topic of chlorinated OPV materials, aiming to provide a guideline for further molecular design.In this Account, first, on the basis of most fundamental features of the Cl atom, we highlight the features of chlorinated materials compared with their fluorinated counterparts: (1) Chlorination is more efficient than fluorination in modulating the optical and electrical properties of OPV materials. In many cases, chlorinated materials show lower energy levels and broader absorption spectra than their fluorinated counterparts, which contribute higher output voltages and current densities in the resulting photovoltaic devices. (2) Cl has a large atomic size than F. On one hand, enhanced overlap of π electrons is beneficial for enhancing the intermolecular packing and crystalline property and thus improving the charge transport. On the other hand, if Cl is introduced inappropriately in the backbone or side chain, this feature will cause a more twisted π plane and larger steric hindrance, having negative impacts on the photovoltaic performance of the corresponding materials. (3) Importantly, chlorination is usually chemically cheaper in synthesis, which has the potential to decrease the material cost of OPV cells. Then, we provide a concise review of chlorinated OPV materials, including polymeric and small-molecule donors and non-fullerene acceptors. The photovoltaic performance in various types of OPV cells using chlorinated materials, such as single-junction, tandem, semitransparent, and indoor-light photovoltaic cells is also discussed. For instance, ultranarrow-band-gap chlorinated acceptors can be used to construct highly efficient color-semitransparent OPV cells, and the wide-band-gap chlorinated materials show great potential for fabricating indoor-light photovoltaic devices. Finally, we briefly discuss current questions related to chlorinated OPV materials and highlight the significance of chlorination in future development.

中文翻译：

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氯化有机光伏材料的最新进展。

概述在过去的几年中，新材料的开发使有机光伏（OPV）电池的功率转换效率（PCE）迅速提高到17％以上，这显示了该技术在不久的将来的商业化潜力。在这一阶段，同时设计具有优异性能和低成本的新材料至关重要。氯化材料正成为具有高PCE的新星，从而形成了一种分子设计趋势，以取代最流行的氟化材料。例如，通过使用氯化的非富勒烯受体，我们最近对单结OPV电池的PCE达到了创纪录的17％。牢记最新进展，在此我们重点关注氯化OPV材料的主题，旨在为进一步的分子设计提供指导。在此帐户中，首先，基于Cl原子的最基本特征，我们重点介绍了氯化材料与氟化物的特征：（1）在调节OPV材料的光学和电学性质方面，氯化比氟化更有效。在许多情况下，氯化材料比氟化材料显示出更低的能级和更宽的吸收光谱，这在所得光伏器件中贡献了更高的输出电压和电流密度。（2）Cl具有比F大的原子尺寸。一方面，增强π电子的重叠有利于增强分子间的堆积和结晶性质并因此改善电荷传输。另一方面，如果在骨架或侧链中不适当引入Cl，此特征将导致扭曲的π平面和更大的空间位阻，对相应材料的光伏性能产生负面影响。（3）重要的是，氯化在化学上通常在化学上较便宜，这有可能降低OPV电池的材料成本。然后，我们简要概述了氯化OPV材料，包括聚合物和小分子供体以及非富勒烯受体。还讨论了使用氯化材料在各种类型的OPV电池中的光伏性能，例如单结，串联，半透明和室内光光伏电池。例如，超窄带氯化物受体可用于构建高效的半透明半透明OPV细胞，宽带隙氯化材料显示出制造室内光光伏器件的巨大潜力。最后，我们简要讨论了与氯化OPV材料有关的当前问题，并强调了氯化在未来发展中的重要性。