2024/10/21 by Ummugulsum Gunes, Michael A. Hope, Yuxuan Zhang +4 · 1 voice
Engineering · Materials Science · #Perovskite Materials and Applications #Conducting polymers and applications
paper · pdf · doi:10.1002/anie.202416938
Abstract Organic‐inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI 3 ), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non‐perovskite phase complicates the application of FAPbI 3 in solar cells. To remedy this, alkali metal cations, most often Cs + , Rb + or K + , are included during perovskite synthesis to stabilize the photoactive phase. The atomic‐level mechanisms of stabilization are complex. While Cs + dopes directly into the perovskite lattice, Rb + does not, but instead forms an additional non‐perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use 1 H− 87 Rb double resonance NMR experiments to show that FA + incorporates into the Rb‐based non‐perovskite phases (FA y Rb 1‐ y Pb 2 Br 5 and δ‐FA y Rb 1‐ y PbI 3 ) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the 1 H and 87 Rb chemical shifts, 1 H− 87 Rb heteronuclear correlation spectra, and 87 Rb 1 H REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60 % FA + incorporation into the inorganic Rb‐based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA + into the non‐perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA‐based perovskites.