Improved Performances of CsPbBr₃ Perovskite Solar Cells via PbI₂ Additive

The emergence of CsPbBr₃ perovskite solar cells (PSCs) with a band gap of approximately 2.3 eV has generated increasing interest stemming from their potential for high open-circuit voltage (V_oc), making them particularly suitable for use in tandem configurations or spectral splitting. However, the V_oc of PSCs currently falls short of its theoretical limit, driven by trap-mediated charge recombination and energy band alignment mismatch. In this study, we present a straightforward additive engineering approach involving the introduction of PbI₂ species into the PbBr₂ precursor film to form the I-Pb-Br interaction, retarding the rapid reaction between PbBr₂ and CsBr. This approach effectively suppresses the Pb-rich phase CsPb₂Br₅, eliminates pinholes on the CsPbBr₃ crystal, and obtains high-quality perovskite films, which can significantly enhance the photovoltaic properties. Consequently, we achieved CsPbBr₃ films characterized by enlarged crystal size, complete coverage, high purity, and without pinhole presence, leading to a best-performed efficiency of 10.35% and a higher V_oc of up to 1.580 V compared to the power conversion efficiency (PCE) of 8.35% and a V_oc of 1.442 V of the control device, along with exceptional operational stability.