Hybrid‐perovskite‐based optoelectronic devices are demonstrating unprecedented growth in performance, and defect passivation approaches are highly promising routes to further improve properties. The modified tandem devices retain ∼93% of their performance over 43 days in a hot and humid outdoor environment of almost 100% relative humidity over 250 h under continuous 1-sun illumination and about 87% during a 85/85 damp-heat test for 500 h, demonstrating the improved phase stability. This enables a stabilized PCE of 28.6% (independently certified at 28.2%) for a monolithic perovskite/silicon tandem solar cell over ∼1 cm² and 27.1% over 3.8 cm², built from a textured silicon heterojunction solar cell. Here, we show how carbazole as an additive to the perovskite precursor solution can not only reduce nonradiative recombination losses but, perhaps more importantly, also can suppress phase segregation under exposure to moisture and light illumination. However, state-of-the-art wide-band-gap perovskite films suffer from phase stability issues. Stacking perovskite solar cells onto crystalline silicon bottom cells in a monolithic tandem configuration enables power-conversion efficiencies (PCEs) well above those of their single-junction counterparts. Our strategy provides an avenue to fabricate efficient and stable wide‐bandgap subcells for multi‐junction photovoltaic devices. With the triple‐cation/triple‐halide wide‐bandgap perovskites enabled by steric engineering, we further obtain a stabilized PCE of 26.0% in all‐perovskite tandem solar cells.
The wide‐bandgap perovskite solar cells exhibit considerably improved performance and photostability, retaining >90% of their initial efficiencies after 1000 hours of operation at maximum power point.
By alloying dimethylammonium and chloride into the mixed‐cation mixed‐halide perovskites, wide bandgaps are obtained with much lower bromide contents while the lattice strain and trap densities are simultaneously minimized. Here we report a steric engineering to obtain high‐quality and photostable wide‐bandgap perovskites (∼1.8 eV) suitable for all‐perovskite tandems. However, the stability and efficiency of wide‐bandgap perovskite solar cells are constrained by the light‐induced halide segregation and by the large photovoltage deficit. Wide‐bandgap (∼1.8 eV) perovskite is an crucial component to pair with narrow‐bandgap perovskite in low‐cost monolithic all‐perovskite tandem solar cells.
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