A Medium-Bandgap Nonfullerene Acceptor Enabling Organic Photovoltaic Cells with 30% Efficiency under Indoor Artificial Light
Tao Zhang, Cunbin An*, Ye Xu, Pengqing Bi, Zhihao Chen, Jingwen Wang, Ni Yang, Yi Yang, Bowei Xu, Huifeng Yao, Xiaotao Hao, Shaoqing Zhang and Jianhui Hou*
Adv. Mater., 2022, 34, 2207009.
The correlation between molecular structure and photovoltaic performance is lagging for constructing high-performance indoor organic photovoltaic (IOPV) cells. Herein, this relationship is investigated in depth by employing two medium bandgap non-fullerene acceptors (NFAs). The newly synthesized NFA of FTCC-Br exhibits a similar optical gap and molecular energy level, but a much stronger dipole moment and larger average electrostatic potential (ESP) compared with the ITCC. After blending with the polymer donor PB2, the PB2:ITCC and PB2:FTCC-Br blends exhibit favorable bulk heterojunction (BHJ) morphologies and the same driving force, but the PB2:FTCC-Br blend exhibits a large ESP difference. In organic photovoltaic (OPV) cells, the PB2:ITCC-based device produces a decent power conversion efficiency (PCE) of 11.0%, whereas the PB2:FTCC-Br-based device gives a PCE of up to 14.8% with an open-circuit voltage (VOC) of 1.05 V, which is the highest value among organic photovoltaic cells with VOCs above 1.0 V. When both acceptor-based devices work under 1000 lux of 3000 K light-emitting diode (LED), the PB2:ITCC-based 1 cm2 device yields a good PCE of 25.4%; in contrast, the PB2:FTCC-Br-based 1 cm2 device outputs an outstanding PCE of 30.2%, which is the best PCE among IOPV cells. These results suggest that a large ESP offset in photovoltaic materials is important for achieving high-efficiency OPV cells.