28.2%-efficient, outdoor-stable perovskite/silicon tandem solar cell

•A strategy to suppress halide segregation and reduce nonradiative recombination loss •Certified 28.2% efficient perovskite/silicon tandem solar cells on a textured structure •Significant stability improvement upon carbazole treatment Stacking perovskite onto crystalline silicon bottom in monolithic configuration enables power-conversion efficiencies (PCEs) well above those of their single-junction counterparts. However, state-of-the-art wide-band-gap films suffer from phase issues. Here, we show how as an additive the precursor solution can not only losses but, perhaps more importantly, also under exposure moisture light illumination. This stabilized PCE 28.6% (independently certified at 28.2%) for cell over ?1 cm2 27.1% 3.8 cm2, built heterojunction cell. The modified devices retain ?93% performance 43 days hot humid outdoor environment almost 100% relative humidity 250 h continuous 1-sun illumination about 87% during 85/85 damp-heat test 500 h, demonstrating improved stability.