Two-Pronged Effect of Warm Solution and Solvent-Vapor Annealing for Efficient and Stable All-Small-Molecule Organic Solar Cells

Herein, a portfolio strategy of warm solution and solvent-vapor annealing (WS+SVA) is employed to subtly manipulate the morphology of small molecular active layers. The WS will increase the molecular solubility and shorten the molecular organization time, and thereby restrain the molecular aggregation during the blend film formation, leading to homogeneous molecular distribution and imporous blend films. Based on the blend films with WS, the SVA treatment can further afford a driving force for tuning phase separation and molecular arrangement after the blend film formation. The WS+SVA-based all-small-molecule organic solar cells (ASM-OSCs) with B1:BTP-eC9 as active layer deliver a champion power conversion efficiency (PCE) of 15.68% with better stability, which is mainly attributable to the enhanced light absorption, charge generation, and extraction. Moreover, the 15.68% PCE should be among the highest values for binary ASM-OSCs. This work proves a promising method to remove the obstacle of morphological modulation for improving the performance of ASM-OSCs.