High-performance bifacial semitransparent organic photovoltaics featuring a decently transparent TeO2/Ag electrode

Abstract

The development of bifacial semitransparent organic photovoltaics (ST-OPVs) is hindered by the limited choice of suitable rear transparent electrodes. Herein, tellurium oxide (TeO₂) featuring a high refractive index and negligible optical absorption is incorporated as the optical coupling layer atop the ultrathin Ag electrode to control the optical interference between the transmitted light into the OPV device and the reflected light by a relatively thin Ag film. The corresponding champion bifacial ST-OPVs based on PM6:Y6:PC₇₁BM with Ag/TeO₂ (11/40 nm) exhibited a high power conversion efficiency (PCE) of 10.14% illuminated from the ITO side and a decent PCE of 9.18% from the Ag side. Apart from the dramatically enhanced bifaciality factor from 49.09% to 90.53%, this integration also significantly improves the average visible transmittance (AVT) from 19.20% to 27.83%, the color-rendering index (CRI) from 74.56 to 88.28, and the light utilization efficiency (LUE) from 2.32%/1.14% to 2.82%/2.32%. In parallel, the TeO₂ layer endowed the PTB7-Th:IEICO-4F system with higher values of AVT, LUE, bifaciality factor and CRI in the corresponding ST-OPVs. Our results demonstrate that the application of an Ag/TeO₂ rear electrode offers a versatile, facile, and universal approach to upgrading the performance of bifacial ST-OPVs towards commercial applications.