All‐in‐One Self‐Assembled Donor–Acceptor Dyad Reaching over 8% Efficiency in Single‐Molecular Organic Photovoltaics

Single‐molecular organic photovoltaics (SMOPVs), which are based on monadic systems containing donor (D) and acceptor (A) molecule blocks that facilitate exciton dissociation, offer obvious advantages over binary or multicomponent bulk‐heterojunction (BHJ) systems, including simplified cell fabrication, stabilized morphology of the D/A interface, and extended device operation lifetime. However, limited by the development of A blocks, the power conversion efficiency (PCE, ≈5%) of SMOPVs based on molecular D–A dyads still lags conventional BHJ OPVs (over 19%). Herein, by introducing a narrow‐bandgap A–DA’D–A conjugated backbone as the A‐block, combined with the linear D‐block BDT‐3T‐R and flexible alkyl chain linker, two molecular dyads, SM‐1Y (one D‐block and one A‐block) and SM‐2Y (one D‐block and two A‐blocks), are designed and developed. Due to superior absorption spectra and better molecular stacking compared to SY‐1Y, SM‐2Y‐based SMOPV delivers a PCE of 8.13%, which is the highest value in the SMOPV reported thus far. Note that both SM‐1Y and SM‐2Y devices show much better storage and photostability stability as compared to the control BDT‐3T‐C6:Y18‐C3 binary system.