A NiSe layer enhanced the efficiency of hole-conductor-free MAPbI3 perovskite solar cells

Interfacial defects between the perovskite layer and the adjacent charge transport layer play a crucial role in enhancing the power conversion efficiency (PCE) and stability of organic–inorganic halide perovskite solar cells. In this study, we employed a transition metal-containing selenide (NiSe) to modify the interface between the electron transport layer and the perovskite layer. Ni2+ as a transition metal exhibits a strong propensity for forming octahedral complexes with halide ions, thereby providing a favorable substrate for perovskite crystallization. This significantly contributes to the reduction of defect densities and the fabrication of high-quality perovskite thin films. Our findings indicate that the grain size of the perovskite films markedly increased upon modification with 0.4 mg mL−1 NiSe, resulting in a reduction of defect density from 2.175 × 1016 cm−3 to 1.485 × 1016 cm−3. Furthermore, the PCE of the NiSe-modified device, at a concentration of 0.4 mg mL−1, reached 14.85%, a significant improvement compared to that of the unmodified device (12.14%). These results offer a novel approach to fabricate perovskite films with enhanced crystallinity and reduced trap density.