Improving efficiency and water–oxygen barrier of perovskite solar cells through phenylalanine additives

Perovskite solar cells (PSCs) show strong potential in the photovoltaic field, but their limited material stability hinders industrial-scale application. Major challenges include degradation of the perovskite structure caused by water and oxygen, as well as uncontrolled crystallization that leads to defects and non-radiative recombination, reducing the device's power conversion efficiency (PCE). This work introduces phenylalanine (PHE) into the precursor solution. The large-sized benzene ring of PHE enhances the film's resistance to water and oxygen. In addition, the water–oxygen adsorption energy of perovskite materials is calculated based on density functional theory simulation, and the steric effects of PHE is quantified. Meanwhile, the Lewis basicity of PHE promotes directional crystallization and defect passivation of the perovskite layer. The optimized PSCs achieve a PCE of 21.49%. The T90 lifetime reaches 1008 h at room temperature and humidity (25 °C, 40% RH), and exceeds 1150 h in a desiccator (25 °C, 10% RH).