Tailoring selenium alkyl chain-containing small molecule donor enables efficient ternary solar cells with reduced charge recombination

Abstract

The introduction of guest materials into binary organic solar cells (OSCs) represents a prominent approach to enhancing the efficiency of OSCs. Here, ternary solar cells were fabricated utilizing a tailored selenium alkyl chain-containing small molecule donor (T3) as the guest donor. The corresponding T3:Y6-based binary OSCs exhibit superior power conversion efficiency (PCE = 13.89 %) than T2:Y6 blends (PCE = 11.80 %), due to the improved morphology, suppressed charge recombination, and enhanced charge transport. When incorporated into the PM6:Y6 host system, T3 based ternary OSCs also demonstrated minimized charge recombination and more efficient charge transport than T2 based ternary OSCs. Consequently, the PCE was promoted from 16.40 % to 17.38 % with simultaneously enhanced VOC, JSC, and FF. Grazing incidence wide-angle X-ray scattering (GIWAXS) reveals that the PM6:Y6 blends are less textured than those of PM6:Y6:T3, while space-charge limited currents reveal lower and unbalanced hole/electron mobility in PM6:Y6 versus PM6:Y6:T3 blend. Charge recombination dynamics, transient absorption, and donor-acceptor miscibility additionally support the improvement. Finally, ternary solar cells PM6:BTP-eC9:T3 realized an impressive PCE of 18.39 % with an enhanced VOC and JSC.