An efficient TeO2/Ag transparent top electrode for 20%-efficiency bifacial perovskite solar cells with a bifaciality factor exceeding 80%

Abstract

Bifacial photovoltaic technology has been established as an effective strategy for increasing electric power generation while reducing the area-related costs of silicon solar cells. For third-generation solar cells of organolead halide perovskites, the monofacial power conversion efficiency (PCE) has exceeded 23%. Therefore, the development of efficient bifacial cells is expected, but the top transparent electrode is a crucial obstacle that must be overcome. In this work, ultrathin silver (Ag) film was selected as the top transparent electrode and, particularly, a tellurium oxide (TeO₂) optical coupling layer was adopted to enhance the transmittance of the Ag film in the visible light region, which markedly increased the light absorption of devices. Compared with PSCs with a pure Ag electrode, the device with a TeO₂ (40 nm)/Ag (11 nm) top electrode showed significantly enhanced bifacial short-circuit current-density and bifacial PCEs of 18.86% (illuminated from the ITO electrode) and 15.12% (illuminated from the Ag electrode). Consequently, in addition to its role as a transmittance enhancement layer, TeO₂ acted as a back reflector when the device was illuminated from the ITO side. Furthermore, a previously proposed phenylethylammonium iodide treatment method was adopted to improve charge transport at the perovskite/fullerene interface. Remarkably, the device achieved champion bifacial PCEs of 20.96% (ITO side) and 17.36% (Ag side), a bifaciality factor of 82.82%, and a steady PCE output and good reproducibility. The large-area device (1 cm²) achieved bifacial PCEs of 12.42% (ITO side) and 10.55% (Ag side), with better performance predicted by simulations. Therefore, the TeO₂/Ag films are promising transparent electrodes for fabricating cost-effective bifacial PSCs.