Improving Molecular Planarity by Changing Alky Chain Position Enables 12.3% Efficiency All-Small-Molecule Organic Solar Cells with Enhanced Carrier Lifetime and Reduced Recombination

摘要

Molecular stacking plays an important role in defining the active layer morphologyin all-small-molecule organic solar cells (ASM OSCs). However, theprecise control of donor/acceptor stacking to afford optimal phase separationremains challenging. Herein, the molecular stacking of a small-molecule donoris tuned by changing the alky chain position to match a high-performancesmall-molecule nonfullerene acceptor (NFA), Y6. The alky chain engineering notonly affects the planarity of the small-molecule donor, but also the molecularaggregation and the active layer morphology, and thus the photovoltaic performance.Notably, single-junction ASM OSCs with 12.3% power conversionefficiency (PCE) are achieved. The PCE of 12.3% is among the top efficiencies ofsingle-junction ASM OSCs reported in the literature to date. The resultshighlight the importance of fine-tuning the molecular structure to achievehigh-performance ASM OSCs.