SOLID-STATE NMR STUDY OF MULTIPLE-CATION LEAD MIXED-ALIDE PEROVSKITE WITH HIGH EFFICIENCY

Hybrid metal-halide perovskites have emerged as highly interesting materials for various applications, such as thin-?lm photovoltaics or light-emitting devices, due to their outstanding optoelectronics properties. A main advantage of these materials is the fact that their macroscopic properties are intrinsically related to their microscopic features (i.e. atomic and molecular organization and dynamics), so mixtures of di?erent cations and anions can be used to tune the optoelectronic properties and to enhance e?ciencies and stabilities. Several variations to the perovskite structure have been tested. In particular, the use of mixed-ion structures, in which the compositional complexity is increased by introducing dopants into the perovskite structure, has resulted in a remarkable improvement in perovskite solar cell performance. Some of the latest top e?ciencies have been reached by multiple-cation lead mixed-halide perovskites (Cs,FA,MA)Pb(I,Br)3. However, the role of the dopants and additives in the high performance of the perovskite solar cells has not been fully understood yet, and its transferability to other perovskites is not straightforward. For this reason, it is important to be able to gain atomic-level understanding of these materials. Solid-State NMR (SSNMR) spectroscopy is strongly sensitive to the local chemical environment, and as such, it proved to be a perfectly suited technique to investigate mixed perovskites. In this study, we focused on the perovskite with formula Cs0:05FA0:81MA0:14PbI2:55Br0:45 because of its high performance. We investigated it by means of SSNMR for the ?rst time, with MAPbI3 being used a reference compound. 207Pb, 13C and 1H high-resolution SSNMR experiments allowed us to characterize the structure and composition of the samples, highlighting phase homogeneity and/or segregation, and to investigate ion dynamics by exploiting both spectral and relaxation properties.