Soft sputtering of NIR-transparent InGaTiO top electrodes on semi-transparent perovskite solar cells for perovskite-Si tandem solar cells

Achieving high-efficiency perovskite–silicon tandem solar cells can only be accomplished through the development of semi-transparent perovskite solar cells (STPSCs) with transparent top and bottom electrodes. In this study, we propose Ga and Ti co-doped In₂O₃ (IGTO) as a near-infrared (NIR) transparent top electrode. The electrode was fabricated via a specially designed isolated plasma soft deposition (IPSD) system to minimize plasma-induced damage caused by the bombardment of energetic particles. Despite being processed at room temperature, the IPSD-grown IGTO electrode exhibited high carrier mobility (≈ 77 cm² V⁻¹ s⁻¹), excellent optical transparency (> 90 % in the visible and NIR regions), low sheet resistance (28 Ω sq⁻¹), and a smooth surface (roughness ≈ 0.4 nm). A STPSC incorporating the IPSD-grown IGTO electrodes achieved a power conversion efficiency (PCE) of 18.71 %, with a NIR transmittance of 88.8 %. Compared to conventional indium tin oxide (ITO)-based tandem cells, the IGTO-based tandem cell demonstrated an enhanced short-circuit current density when integrated into a four-terminal perovskite/Si tandem configuration, resulting in a PCE of 26.05 %. These findings highlight the potential of IPSD-grown plasma damage-free IGTO as a promising alternative to conventional ITO electrodes for high-performance tandem solar cells.