Room-Temperature Sputtered Cerium-Doped Indium Oxide Transparent Conducting Electrodes for Bifacial Perovskite Solar Cells: Albedo Utilization and Perovskite/Silicon Tandems

Bifacial perovskite solar cells (PSCs) offer the potential for higher power output through tandem configurations with silicon solar cells or by harvesting light from both sides. A high-transmittance and low-resistance transparent electrode is crucial for bifacial PSCs. However, the most widely used transparent conductive oxide (TCO) as transparent electrodes often require energetic ion bombardment during deposition and high post-annealing temperatures to obtain high transmittance and low resistance, making them incompatible for direct deposition onto delicate perovskite films. In this work, a cerium-doped indium oxide (ICO) film, prepared via radio frequency (RF) magnetron sputtering at room temperature (RT), is employed as the top transparent conductive electrode in bifacial PSCs. A 20 nm MoOx layer is introduced as a buffer layer to protect the underlying spiro-OMeTAD and perovskite layers against sputtering damage. The ICO film, deposited with an RF power of 80 W for 1 h and 20 min at RT, exhibits an amorphous structure with a thickness of 210 nm, a mobility of 8.3 cm2/Vs, a carrier concentration of 6.07 × 1020 cm⁻3, a resistivity of 1.24 × 10−3 Ω·cm, and an average transmittance of 89.70% between 550 nm and 1000 nm, resulting in a figure of merit (FOM) of 6.67 × 10−3 Ω−1. The fabricated bifacial PSC demonstrates power conversion efficiencies (PCEs) of 15.28% and 10.00% when illuminated from the FTO side and ICO side, respectively. Furthermore, the bifacial PSC under simultaneous illumination from both sides achieves a superior power density compared to the monofacial PSC in albedo utilization. Finally, by mechanically stacking the bifacial PSC as the top cell with a passivated emitter rear contact (PERC) crystalline silicon solar cell as the bottom cell, the 4-terminal perovskite/silicon tandem solar cell achieves a PCE of 21.89%.