High performance wide bandgap perovskite solar cell with low VOC deficit less than 0.4 V

Wide bandgap perovskite solar cells (PSCs) have attracted significant attention because they can be applied to the top cells of tandem solar cells. However, high open-circuit voltage (VOC) deficit (>0.4 V) result from poor crystallization and high non-radiative recombination losses become a serious limitation in the pursuit of high performance. Here, the relevance between different PbI2 proportions and performance parameters are revealed through analysis of surface morphology, residual stress, and photostability. The increase of PbI2 proportion promotes crystal growth and reduces the work function of the perovskite film surface and promotes the energy level alignment with the carrier transport layer, which decreased the VOC deficit. However, residual PbI2 exacerbated the stress level of perovskite film, and the resulting lattice disorder deteriorated the photostability of the device. Ultimately, after the synergistic passivation of residual PbI2 and PEAI, the VOC achieves 1.266 V and VOC deficit is less than 0.4 V, the record value in wide bandgap PSCs.