Ligand‐Modulated Excess PbI2 Nanosheets for Highly Efficient and Stable Perovskite Solar Cells. Issue 21 (13th April 2020) - Wang, Huanhuan
Abstract: Excess lead iodide (PbI2 ), as a defect passivation material in perovskite films, contributes to the longer carrier lifetime and reduced halide vacancies for high‐efficiency perovskite solar cells. However, the random distribution of excess PbI2 also leads to accelerated degradation of the perovskite layer. Inspired by nanocrystal synthesis, here, a universal ligand‐modulation technology is developed to modulate the shape and distribution of excess PbI2 in perovskite films. By adding certain ligands, perovskite films with vertically distributed PbI2 nanosheets between the grain boundaries are successfully achieved, which reduces the nonradiative recombination and trap density of the perovskite layer. Thus, the power conversion efficiency of the modulated device increases from 20% to 22% compared to the control device. In addition, benefiting from the vertical distribution of excess PbI2 and the hydrophobic nature of the surface ligands, the modulated devices exhibit much longer stability, retaining 72% of their initial efficiency after 360 h constant illumination under maximum power point tracking measurement. Abstract : State‐of‐the‐art perovskite solar cells generally consist of an excess of lead iodide (PbI2 ) as passivator. In this work, ligand‐modulation technology is demonstrated to fabricate vertically distributed PbI2 nanosheets between the perovskite grain boundaries, which enhances the passivation effect of PbI2 and improves the power conversion efficiency and stability of perovskite solar cells.