Design of a Fully Non-Fused Bulk Heterojunction toward Efficient and Low-Cost Organic Photovoltaics
Lijiao Ma, Shaoqing Zhang,* Junzhen Ren, Guanlin Wang, Jiayao Li, Zhihao Chen, Huifeng Yao, and Jianhui Hou*
Angew. Chem. Int. Ed. 2023, e202214088
To modulate the miscibility between donor and acceptor materials both possessing fully non-fused ring structures, a series of electron acceptors (A4T-16, A4T-31 and A4T-32) with different polar functional substituents were synthesized and investigated. The three acceptors show good planarity, high conformational stability, complementary absorption and energy levels with the non-fused polymer donor (PTVT-BT). Among them, A4T-32 possesses the strongest polar functional group and shows the highest surface energy, which facilitates morphological modulation in the bulk heterojunction (BHJ) blend. Benefiting from the proper morphology control method, an impressive power conversion efficiency (PCE) of 16.0% and a superior fill factor over 0.796 are achieved in the PTVT-BT:A4T-32-based organic photovoltaic cells with superior photoactive materials price advantage, which represent the highest value for the cells based on the non-fused blend films. Notably, this cell maintains ~84% of its initial PCE after nearly 2000 h under the continuous simulated 1-sun-illumination. In addition, the flexible PTVT-BT:A4T-32-based cells were fabricated and delivered a decent PCE of 14.6%. This work provides an effective molecular design strategy for the non-fused NFAs from the aspect of bulk morphology control in fully non-fused BHJ layers, which is crucial for their practical applications.