Temperature-Resilient Monolithic Perovskite/Silicon Tandems Enabling Crystalline Front TCO Integration

Front transparent conductive oxides (TCOs) that combine high conductivity with broadband transparency are essential to minimize resistive and optical losses in perovskite/silicon tandem solar cells. While indium zinc oxide (IZO) is a commonly used front electrode, its amorphous nature leads to undesired absorption losses near the band edge, thereby constraining the tandem current. Here, we explore the use of crystalline Zr-doped indium oxide (IZrO), featuring a higher transparency at its band edge, to replace IZO as the front electrode. Full crystallization of IZrO requires postannealing at temperatures >190 °C, which raises concerns around its compatibility with typically employed charge transport layers and the perovskite layer itself. Our work reveals that hole- and electron-selective contacts (NiO_x/MeO-2PACz and C₆₀/SnO₂, respectively) as used in our tandems endure such temperatures. Conversely, the wide bandgap CsFAMAPbI_xBr_3–x perovskite composition, deposited by solution and sequential hybrid processes, degrades upon high-temperature annealing. Notably, we identified substantial differences between the solution- and hybrid-processed perovskites through comprehensive analysis, where the latter exhibited higher temperature resilience. As a result, only hybrid-processed perovskite/silicon tandem devices partially retained their initial power conversion efficiency after high-temperature annealing. Our work underlines the urgency to develop high-temperature-resilient perovskites to advance perovskite/silicon tandem photovoltaics to their full performance potential, and, arguably, to improve their overall reliability under thermal stress.