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In situ NMR Investigation of the Photoresponse of Perovskite Crystal
54 Pages Posted: 24 Apr 2020 Publication Status: Published
More...Abstract
Hybrid perovskites have many excellent properties that make them outstanding candidates for use in optoelectronic devices. Nonetheless, hybrid perovskites present numerous fundamental issues that are not yet fully understood. The present study seeks to address this problem by reporting on the occurrence of ultraslow dynamic orientation changes in the methylammonium (MA) cations and the corresponding changes in the inorganic lattice of MAPbI3 perovskite crystals occurring over a time scale of 100 s under continuous illumination based on in situ single crystal 2H nuclear magnetic resonance (NMR) and in situ X-ray diffraction results. The observed ultraslow dynamic changes in MAPbI3 have not been previously reported. The time scale is far greater than those of elementary molecular motions in MAPbI3 that typically occur over time scales ranging from femtoseconds to picoseconds. The DFT calculation reveals that the orientation changes of the MA cations can induce the change in the band gap energy of MAPbI3. The demonstrated ultraslow orientation changes of the MA cations in MAPbI3 under illumination are correlated with the photoresponse observed in the single crystal optoelectronic device, providing a new viewpoint for understanding the molecular origins of the stabilization process in the photoresponse of devices based on MAPbI3.
Keywords: Perovskite crystal, in-situ single crystal 2H NMR, DFT calculation, Ultraslow cation dynamics, Stabilization process of photoresponse
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