Side-chain symmetry-breaking strategy on porphyrin donors enables high-efficiency binary all-small-molecule organic solar cells

Abstract

Side-chain symmetry-breaking strategy plays an important role in developing photovoltaic materials for high-efficiency all-small-molecule organic solar cells (ASM OSCs). However, the power conversion efficiencies (PCEs) of ASM OSCs still lag behind their polymer-based counterparts, which can be attributed to the difficulties in achieving favorable morphology. Herein, two asymmetric porphyrin-based donors named DAPor-DPP and DDPor-DPP were synthesized, presenting stronger intermolecular interaction and closer molecular stacking compared to the symmetric ZnP-TEH. The DAPor-DPP:6TIC blend afforded a favorable morphology with nanoscale phase separation and more ordered molecular packing, thus achieving more efficient charge transportation and suppressed charge recombination. Consequently, the DAPor-DPP:6TIC-based device exhibited superior photovoltaic parameters, yielding a champion PCE of 16.62% higher than that of the DDPor-DPP-based device (14.96%). To our knowledge, 16.62% can be ranked as one of the highest PCE values among the binary ASM OSC filed. This work provides a prospective approach to address the challenge of ASM OSCs in improving film morphology and further achieving high efficiency via side-chain symmetry-breaking strategy, exhibiting great potential in constructing efficient ASM OSCs.

Keywords

all-small-molecule organic solar cells / asymmetric side-chain engineering / power conversion efficiency / small molecule donors

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2024 The Author(s). SusMat published by Sichuan University and John Wiley & Sons Australia, Ltd.