Polymer solar cells using non-fullerene acceptors are nowadays amongst the most promising approaches for next generation photovoltaic applications. However, there are still remaining challenges related to large-scale fully solution-processing of high efficiency solar cells as high efficiencies are obtained only for very small areas using hole transport layers based on evaporated molybdenum oxide. Solution-processable hole transport materials compatible with non-fullerene acceptor materials are still scarce and thus considered as one of the major challenges nowadays. In this work, we present copper-doped nickel oxide nanocrystals that form highly stable inks in alcohol-based solutions. This allows processing of efficient hole transport layers in both regular and inverted device structures of polymer solar cells. As the initial work function of these ionic doped materials is too low for efficient hole extraction, doping the nanocrystals with an organic electron acceptor, namely 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquino dimethane (F4-TCNQ), was additionally applied to make the work function more suitable for hole extraction. The resulting hybrid hole transport layers were first studied in polymer solar cells based on fullerene acceptors using regular device structures yielding 7.4% efficiency identical to that of reference cells based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). For inverted device structures, the hybrid hole transport layers were processed on top of blends based on the non-fullerene acceptor IT-4F and PBDB-T-2F donor. The corresponding solar cells showed promising efficiencies up to 7.9% while the reference devices using PEDOT:PSS showed inferior performances. We further show that the hybrid hole transport layer can be used to tune the color of the polymer solar cells using optical spacer effects.

中文翻译：

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有机-无机掺杂的氧化镍纳米晶体用于颜色可调的反向聚合物太阳能电池中的空穴传输层

如今，使用非富勒烯受体的聚合物太阳能电池已成为下一代光伏应用最有前途的方法之一。然而，仍然存在与高效太阳能电池的大规模完全溶液处理有关的挑战，因为仅使用基于蒸发的氧化钼的空穴传输层仅在非常小的区域内才能获得高效率。与非富勒烯受体材料相容的可溶液加工的空穴传输材料仍然很稀少，因此被认为是当今的主要挑战之一。在这项工作中，我们提出了铜掺杂的氧化镍纳米晶体，它们在醇基溶液中形成高度稳定的油墨。这允许在聚合物太阳能电池的规则和倒置器件结构中处理有效的空穴传输层。由于这些离子掺杂材料的初始功函数太低，无法有效地进行空穴提取，因此在纳米晶体中掺杂了有机电子受体，即2,3,5,6-四氟-7,7,8,8-四氰基喹甲烷（F4 -TCNQ），另外使功函更适合于孔提取。最初在基于富勒烯受体的聚合物太阳能电池中使用常规器件结构研究所得的杂化空穴传输层，其效率与基于聚（3,4-乙撑二氧噻吩）：聚苯乙烯磺酸盐（PEDOT：PSS）的参考电池相同，效率为7.4％。对于倒置器件结构，基于非富勒烯受体IT-4F和PBDB-T-2F供体，在共混物之上对混合空穴传输层进行了处理。相应的太阳能电池效率高达7。9％，而使用PEDOT：PSS的参考设备则表现较差。我们进一步表明，杂化空穴传输层可用于利用光学间隔效应来调节聚合物太阳能电池的颜色。