Simultaneous Enhancement of Efficiency and Photostability in Wide-Bandgap Perovskite Solar Cells via Managing Residual PbI ₂ with a Phosphoramide Additive

In wide-bandgap perovskite solar cells (WBG-PSCs), the addition of excess lead salts in a perovskite precursor is a popular strategy for fabricating high-efficiency devices. The presence of lead iodide (PbI 2 ) in perovskite films has been confirmed to enhance the device performance but introduces the intrinsic instability of perovskite under illumination due to its photodecomposition. In this work, we used tri( N, N -tetramethylene)phosphoramide (TPPA) as an additive to manage residual PbI 2 in perovskite films, which regulates the crystallization process of mixed-halide perovskites, promotes the formation of high-quality perovskite films, and stabilizes the perovskite films under light irradiation. As a result, WBG-PSCs with a band gap of 1.76 eV achieved a high open-circuit voltage close to 1.34 V and power conversion efficiency (PCE) of 21.4%. Furthermore, the devices with TPPA retained 90% of the initial PCE after 750 h during the maximum power point tracking process, while the control devices only retained 90% of the initial PCE after 270 h.