Effects of light irradiation on the photovoltaic performance and crystal lattices of organic–inorganic perovskites in solar cells

The photodurability of unencapsulated methylammonium-based perovskite solar cells prepared with different device configurations using different precursor solution compositions was investigated. Devices with a decaphenylcyclopentasilane layer on the perovskite layer exhibited higher durability against light irradiation. The photovoltaic performance of the light-irradiated devices recovered to levels close to those before the maximum power point tracking measurements after 1 week of storage in a darkroom. Lattice expansion due to light irradiation and contraction upon storage in the dark were observed, possibly due to the displacement of the atoms and molecules. First-principles calculations on the dimethylammonium-added perovskites indicated that the activation energy for atomic diffusion was reduced, suggesting that the atoms could diffuse more rapidly as the lattice expanded under light irradiation. The photovoltaic performance improved owing to the slow migration of atoms and molecules to their original atomic sites during room-temperature aging in the dark. This study contributes to the elucidation of the recovery mechanisms of the photovoltaic properties of perovskite solar cells, which are expected as next-generation energy devices.