Synthesis and Optical Properties of Macroscopic and Low-Dimensional CsPbBr₃ Perovskite Crystals

Hybrid perovskite crystals MPbX₃ have recently emerged as novel opto-electronic materials that hold promise for photovoltaics, photodetection, light emitting diodes and laser devices. Their performance is related to the high light absorption coefficient, high charge carrier mobility, and long exciton diffusion length. Their relatively weak (photo)chemical stability is a drawback. Alternatively, the all-inorganic CsPbX₃ systems are also under extensive investigation. Cesium ions replace the organic part, while the amine and acid ligands can stabilize the perovskite phase even under ambient conditions. The photoluminescence quantum yield can be as high as 90% [1]. The nanocrystal shape (and thus the band structure and optical properties) can be tuned via ligand engineering or by changing the reaction conditions. Recently, Bekenstein et al. showed that 2D nanosheets of CsPbBr₃ perovskite can be prepared, besides cubic nanocrystals [2].

Here we show for the CsPbBr₃ compound, how quasi 2-D and macroscopic CsPbBr₃ crystals can be formed from self-assembled cubic nanocrystals, using a destabilization technique. The optical properties of these crystals were investigated with time-resolved photoluminescence spectroscopy at variable temperature, from 4 K to 300 K and PL-excitation spectroscopy. Several sharp optical transitions could be detected. The results and the consequences for the band structure will be discussed in my lecture.

(1) Protesescu, L.; Yakunin, S.; Bodnarchuk, M. I.; Krieg, F.; Caputo,R.; Hendon, C. H.; Yang, R. X.; Walsh, A.; Kovalenko, M. V.; Nano Lett. 2015, 15, 3692−3696.

(2) Bekenstein, Y.; Koscher, B.A,: Eaton, S.W; Yang, P.; Alivisatos, A.P.; J. Am. Chem. Soc, 2016,137 ,51, 16008-16011.