All-small-molecule Organic Solar Cells with Enhanced Efficiency and Stability Enabled by Polymer Additive as a Morphology Modulator

For all-small-molecule organic solar cells (ASM-OSCs), modulating the morphology of active layer has been a challenging and urgent issue to achieve high efficiency and stablity. In this work, a polymer donor PM7 as a morphology modulator was incorporated to a BTTzR:Y6 system to fabricate ternary ASM-OSCs. A small amount of PM7 could promote more favourable nanostructure and ordered molecular packing in the blend film, resulting in more efficient excition dissiociation and charge carrier transport in the device. As a result, the optimal ternary devices exhibited a significantly improved power conversion efficiency (PCE) of 16.0% with simultaneously enhanced short circuit current (J(SC)) and fill factor (FF) compared to the binary devices with a PCE of 13.9%. Notably, after being heated at 85 degrees C for 2200 min, the ternary devices still retained 79% of its initial PCE, whereas the binary devices showed larger decay to 43% in the same duration. The results demonstrated that adding the polymer additive can effectively modulate the blend morphology for highly efficient and stable ASM-OSCs.