40.1% Record Low‐Light Solar‐Cell Efficiency by Holistic Trap‐Passivation using Micrometer‐Thick Perovskite Film

Abstract Perovskite solar cells exhibit not only high efficiency under full AM1.5 sunlight, but also have great potential for applications in low‐light environments, such as indoors, cloudy conditions, early morning, late evening, etc. Unfortunately, their performance still suffers from severe trap‐induced nonradiative recombination, particularly under low‐light conditions. Here, a holistic passivation strategy is developed to reduce traps both on the surface and in the bulk of micrometer‐thick perovskite film, leading to a record efficiency of 40.1% under 301.6 µW cm −2 warm light‐emitting diode (LED) light for low‐light solar‐cell applications. The involvement of guanidinium into the perovskite bulk film and 2‐(4‐methoxyphenyl)ethylamine hydrobromide (CH 3 O‐PEABr) passivation on the perovskite surface synergistically suppresses the trap states. The charge carrier lifetimes of the perovskite film increase by tenfold and fivefold to 981 ns and 8.02 µs at the crystal surface and in its bulk, respectively. The decreased nonradiative recombination loss translates to a high open‐circuit voltage ( V oc ) of 1.00 V, a high short‐circuit current ( J sc ) of 152.10 µA cm −2 , and a fill factor (FF) of 79.52%. Note that this performance also stands as the highest among all photovoltaics measured under indoor light illumination. This work of trap passivation for micrometer‐thick perovskite film paves a way for high‐performance, self‐powered IoT devices.