Increased resistance to photooxidation in Dion-Jacobson lead halide perovskites: Implication for perovskite device stability

2D metal halide perovskites have enabled significant stability improvements in perovskite devices, partic- ularly in resistance to moisture. However, some 2D perovskites are even more susceptible to photooxida- tion compared to 3D perovskites. This is particularly true for more commonly investigated Ruddlesden- Popper (RP) perovskites, which exhibit increased susceptibility to photoinduced degradation compared to Dion-Jacobson (DJ) perovskites. Comparisons between different RP and DJ perovskites reveal that this phenomenon cannot be explained by commonly proposed differences in superoxide ion generation, interlayer distance, or lattice structural rigidity differences. Instead, the resistance to photooxidation of DJ perovskites can be attributed to a decreased likelihood of double deprotonation events (compared to single deprotonation events in RP perovskites) required for the loss of organic cations and perovskite decomposition. Consequently, DJ perovskites are less susceptible to oxidative degradation (induced both photo- and electrochemically), which leads to improved operational stability of solar cells based on these materials.