Semitransparent ternary nonfullerene polymer solar cells exhibiting 9.40% efficiency and 24.6% average visible transmittance

Efficient semitransparent ternary polymer solar cells (PSCs) are fabricated with narrow band gap material PTB7-Th as donor, two narrow band gap nonfullerene materials BDTThIT-4F and IEICO-4F as one alloyed acceptor. Firstly, the content of IEICO-4F in acceptors is optimized in opaque PSCs with 100 nm Ag as electrode, power conversion efficiency (PCE) of the optimized opaque PSCs arrives to 12.03% with 50 wt% IEICO-4F in the alloyed acceptor. The 1 nm Au/10 nm Ag is designed to replace 100 nm Ag as semitransparent electrode. The semitransparent electrode exhibits high transmittance in visible light range and low transmittance in long wavelength range, which is beneficial to improve photon harvesting of active layers prepared with narrow band gap materials. The semitransparent ternary PSCs exhibit a PCE of 9.40% with 24.6% average visible transmittance from 370 nm to 740 nm, which should be among the highest values for semitransparent PSCs. This work indicates that ternary strategy may have great potential in preparing efficient semitransparent PSCs with two narrow band gap nonfullerene materials.