Semitransparent organic solar cells exhibiting 13.02% efficiency and 20.2% average visible transmittance

Semitransparent organic solar cells (OSCs) were fabricated with a broad bandgap polymer D18-Cl as the donor (D), narrow bandgap small molecule Y6-1O as the acceptor (A) and ultra-narrow bandgap material Y6 as the third component. A power conversion efficiency (PCE) of 14.92% can be obtained from opaque OSCs with D18-Cl:Y6-1O (1.1 : 1.6, wt/wt or 0.7 : 1.6, wt/wt) as active layers, which is due to the dependence of the three well-balanced photovoltaic parameters on D18-Cl content in the active layer. It should be highlighted that the average visible transmittance (AVT) of blend films can be markedly enhanced from 30.3% to 47.3% with decrease in D:A from 1.1 : 1.6 to 0.7 : 1.6 (wt/wt), which is highly conducive to the preparation of semitransparent OSCs. Keeping the D:A as constant (0.7 : 1.6, wt/wt), 16.05% PCE is achieved in opaque ternary OSCs with D18-Cl:Y6-1O:Y6 (0.7 : 0.8 : 0.8, wt/wt) as the active layers, resulting from the slightly increased JSC of 23.21 mA cm−2 and FF of 76.74%. The AVT of the corresponding ternary blend films is also improved to 50.1%. Semitransparent ternary OSCs are fabricated with Au (1 nm)/Ag (20 nm, 15 nm, 10 nm) replacing 100 nm Ag as the electrode. A PCE of 13.02%, an AVT of 20.2% and light utilization efficiency of 2.63% are obtained from the semitransparent OSCs with Au (1 nm)/Ag (10 nm) as the electrode. This work indicates that adjusting D:A weight ratio and employing a ternary strategy should have great potential in simultaneously improving the PCE and AVT of semitransparent OSCs, especially using a wide bandgap polymer as the donor.