Synthesis and photophysical properties of small-molecule donor materials for organic solar cells featuring a benzodithiophene core with phenylthio side chains and branched alkyl chain end groups

The key way to improve the photovoltaic performance of all small molecule organic solar cells (ASM-OSCs) is to achieve the best form to achieve effective charge generation and transmission. Here, we synthesized a new small molecular donor material, SM-mB-sBu, which is based on the functionalization of benzothiophene (BDT) core and phenylthio side chain. The material was synthesized by direct Knoevenagel condensation between dialdehyde compound 1 and terminal group 2. SM-mB-sBu shows excellent solubility in common organic solvents. Small molecular donors show broad and strong absorption spectra, and the calculated wide band gap is 1.82 eV, which can overlap with the complementary spectra of most non-fullerene receptors (NFA) to achieve high efficiency OSCs. This well-matched energy level arrangement and strong light collection ability contribute to effective exciton dissociation and charge transfer in the obtained bulk heterojunction (BHJ) active layer.