Narrow bandgap molecular dyads Incorporating Y-series acceptor backbones for efficient single-molecular organic solar cells

The performance of organic solar cells (OSCs) is mainly related to the bulk heterojunction (BHJ) microstructure of specific active layer systems, which is often in a metastable state. A promising strategy to address the abovementioned shortcomings of BHJs is to develop single-component active layer materials. Owing to the single-component small molecule materials with defined chemical structures generally exhibit poor absorption spectra, herein we first introduced narrow bandgap Y-series acceptors into the molecular skeleton of single-component materials, and designed two molecular dyads, SM-Et-1Y and SM-Et-2Y. The optical bandgaps ( E_g^opts ) of the two dyads are 1.364 and 1.361 eV, respectively, which are much smaller than those of previously reported single-component molecules. Consequently, the SM-Et-2Y-based single-component OSCs (SCOSCs) showed a power conversion efficiency (PCE) of 5.07