UV Degradation of Perovskite Solar Cells: TiO2 Photocatalysis and UV Filters

… more less UV degradation of perovskite solar cells comes from the highest-energy part of sunlight. UV photons carry enough energy to drive chemistry, not just make current. They harm the cell in two main ways. First, a titanium dioxide (TiO2) electron layer acts as a photocatalyst under UV. That means it uses light energy to drive a reaction. At the TiO2 surface, it pulls electrons from iodide and breaks down the perovskite next to it. Second, UV slowly breaks down organic layers, such as hole transport layers and some plastic encapsulants, which can turn yellow. On a stability plot you see a cell that holds up under a lamp with no UV but fades under full sunlight. That pattern points to UV, not heat or water. There are several fixes. Swap TiO2 for tin oxide (SnO2), which is far less active. Add a thin layer between the oxide and the perovskite. Put a UV filter on the front, or a down-shifting layer that turns UV into visible light the cell can use. The trade-off is small: a UV filter costs a little Jsc, because perovskites do turn some UV into current. When you read a test result, check whether the lamp included UV. After this Concept you can tell UV damage from other causes and pick a fix that fits the cell's layers.