Fused Hexacyclic Nonfullerene Acceptor with Strong Near-Infrared Absorption for Semitransparent Organic Solar Cells with 9.77% Efficiency

A fused hexacyclic electron acceptor, IHIC, based on strong electron-donating group dithienocyclopentathieno[ 3,2-b]thiophene flanked by strong electron-withdrawing group 1,1-dicyanomethylene-3-indanone, is designed, synthesized, and applied in semitransparent organic solar cells (ST-OSCs). IHIC exhibits strong near-infrared absorption with extinction coefficients of up to 1.6 x 10(5) m(-1) cm(-1), a narrow optical bandgap of 1.38 eV, and a high electron mobility of 2.4 x 10(-3) cm(2) V-1 s(-1). The ST-OSCs based on blends of a narrow-bandgap polymer donor PTB7-Th and narrow-bandgap IHIC acceptor exhibit a champion power conversion efficiency of 9.77% with an average visible transmittance of 36% and excellent device stability; this efficiency is much higher than any single-junction and tandem ST-OSCs reported in the literature.