Wang Wei, Li Yuhao, Zhan Chun, Xiao Shengqiang, Tang Chenqing, Li Gongchun, Lu Xinhui, Zhang Qichun
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, P. R. China.
Department of Physics, The Chinese University of Hong Kong, Sha Tin, Hong Kong SAR 999077, P. R. China.
ACS Appl Mater Interfaces. 2020 Nov 4;12(44):49876-49885. doi: 10.1021/acsami.0c13109. Epub 2020 Oct 22.
The morphology of a bulk heterojunction (BHJ) blend within a polymer solar cell (PSC) device plays a crucial role in its performance. The ideal morphology is generally achieved through molecular engineering and optimization under film processing conditions. Under different processing conditions, the deviation of the resulted morphology characteristics from the ideal one leads to the dispersion of device performance. For a specific donor/acceptor BHJ blend, it is of great challenge to maintain an efficient and comparable photovoltaic performance under various processing conditions. The solution to this challenge would be of great value in offering more choices for a suitable processing technology in practical applications. Based on the acceptor BTTFIC with the core of bis(thieno[3,2-]thieno)cyclopentafluorene (BTTF) in our previous work, we chemically modified BTTFIC by fluorination of the end groups of 1,1-dicyanomethylene-3-indanones (IC) and the switching part of octyls in BTTF with 4-hexylphenyls to offer a novel acceptor (BTTFIC4F-Ar). The inverted PBDB-T-2Cl:BTTFIC4F-Ar blend device provided an average power conversion efficiency (PCE) of 10.61, 11.08, and 11.55% when processed under solvent annealing (SA), thermal annealing (TA), and additive treatment with 1,8-diodooctane (DIO), respectively. Different from the reported discrete performance under various processing conditions for a specific donor/acceptor BHJ blend, a low mean absolute performance deviation of 3% was attained. This slight enhancement trend was unexceptionally reflected on charge generation, transportation, and recombination within the blend films from SA, TA, and DIO conditions. A slightly improved ordering of BTTFIC4F-Ar within the DIO blend was observed. Meanwhile, very similar molecular packings as well as a close amorphous domain size of the mixture of PBDB-T-2Cl and BTTFIC4F-Ar within the three blends were observed. These morphological characteristics are in good agreement with the photoelectrical conversion performance of the blends under the three processing conditions. Furthermore, similar attenuation behaviors in performance were also observed. This investigation may provide new guidance on the molecular engineering of nonfullerene acceptors to achieve an efficient BHJ blend with more options for a suitable and cost-effective processing method in practical applications.
聚合物太阳能电池（PSC）器件中本体异质结（BHJ）共混物的形态对其性能起着至关重要的作用。理想的形态通常是通过分子工程以及在薄膜加工条件下进行优化来实现的。在不同的加工条件下，所得形态特征与理想形态的偏差会导致器件性能的分散。对于特定的供体/受体BHJ共混物而言，在各种加工条件下保持高效且可比的光伏性能极具挑战性。解决这一挑战对于在实际应用中为合适的加工技术提供更多选择具有重要价值。基于我们之前工作中以双（噻吩并[3,2 - ]噻吩）环戊并五氟苯（BTTF）为核心的受体BTTFIC，我们通过对1,1 - 二氰基亚甲基 - 3 - 茚酮（IC）的端基进行氟化以及用4 - 己基苯基对BTTF中的辛基交换部分进行化学修饰BTTFIC，从而得到一种新型受体（BTTFIC4F - Ar）。倒置的PBDB - T - 2Cl:BTTFIC4F - Ar共混器件在溶剂退火（SA）、热退火（TA）以及用1,8 - 二碘辛烷（DIO）进行添加剂处理时，平均功率转换效率（PCE）分别为10.61%、11.08%和11.55%。与报道的特定供体/受体BHJ共混物在各种加工条件下的离散性能不同，其平均绝对性能偏差低至3%。这种轻微的增强趋势无一例外地体现在来自SA、TA和DIO条件的共混薄膜内的电荷产生、传输和复合过程中。在DIO共混物中观察到BTTFIC4F - Ar的有序性略有改善。同时，在三种共混物中观察到PBDB - T - 2Cl和BTTFIC4F - Ar混合物具有非常相似的分子堆积以及相近的无定形域尺寸。这些形态特征与三种加工条件下共混物的光电转换性能高度吻合。此外，在性能方面也观察到了类似的衰减行为。这项研究可能为非富勒烯受体的分子工程提供新的指导，以实现高效的BHJ共混物，并在实际应用中为合适且具有成本效益的加工方法提供更多选择。
