Our previous work studied the effect of intercalating cations (large-size alkyl ammonium compared to MA/FA/Cs/K/Rb cations) and their concentrations on the thermal stability of perovskite films. We found that approximately 20–25 mol % of intercalating organic cations into MAPbI3 (nominal n = 4/5) can maximize film stability. However, higher/lower concentrations lead to inferior stability. (Intercalating-organic-cation-induced stability bowing in quasi-2D metal-halide perovskites[J]. ACS Energy Letters, 2021, 7(1): 70-77.)
We also investigated the thermal stability of a series of 2D Ruddlesden−Popper (RP) perovskites using seven types of intercalating cations with increasing linear carbon-chain length from ethylammonium (EA) to n-dodecylammonium (DA). We found long-chain cations in quasi-2D perovskite films lead to strong steric hindrance between adjacent perovskite domains, thus suppressing Ostwald ripening during thermal aging. For short-chain cations, increased-dimensional phase redistribution during aging is observed, which can benefit a concomitant regeneration of the 3D/3D-like perovskite phases. (Advanced Functional Materials 32.43 (2022): 2207101.)
The results show that the 2D perovskites with an n value of 4/5 are widely used as perovskite recipes due to their high stability performance.
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