Highly Efficient Monolithic Perovskite/Perovskite/Silicon Triple‐Junction Solar Cells

Abstract Wide‐bandgap metal halide perovskites have demonstrated promise in multijunction photovoltaic (PV) cells. However, photoinduced phase segregation and the resultant low open‐circuit voltage ( V oc ) have greatly limited the PV performance of perovskite‐based multijunction devices. Here, a alloying strategy is reported to achieve uniform distribution of triple cations and halides in wide‐bandgap perovskites by doping Rb + and Cl − with small ionic radii, which effectively suppresses halide phase segregation while promoting the homogenization of surface potential. Based on this strategy, a V oc of 1.33 V is obtained from single‐junction perovskite solar cells, and a V OC approaching 3.0 V and a power conversion efficiency of 25.0% (obtained from reverse scan direction, certified efficiency: 24.19%) on an 1.04 cm 2 photoactive area can be achieved in a perovskite/perovskite/c‐Si triple‐junction tandem cell, where the certification efficiency is by far the greatest performance of perovskite‐based triple‐junction tandem solar cells. This work overcomes the performance deadlock of perovskite‐based triple‐junction tandem cells by setting a materials‐by‐design paradigm.