Issue 9, 2019

On the origins of the green luminescence in the “zero-dimensional perovskite” Cs4PbBr6: conclusive results from cathodoluminescence imaging

Abstract

There is great interest in the use of highly-efficient all-inorganic halide perovskites CsnPbBr2+n for optoelectronic applications. There however remains considerable debate as to the origins of the green luminescence in the zero-dimensional phase of the perovskite Cs4PbBr6, with theories suggesting it originates either from defects in the Cs4PbBr6 lattice or CsPbBr3 impurities/inclusions. The confusion has arisen due to the two phases being miscible and typically co-existing. Moreover, low impurity levels of CsPbBr3 in Cs4PbBr6 are difficult to detect by XRD measurements, yet have much stronger photoluminescence than bulk CsPbBr3 that exhibits quenching, further contributing to the confusion as to the origins of the green photoluminescence. With the rise of significant debate and misconceptions, we provide conclusive evidence that the green emission from Cs4PbBr6 is indeed due to nanocrystalline CsPbBr3 impurities. This is demonstrated by undertaking cathodoluminescence and EDX measurements on samples prepared mechanochemically by ball-milling. Cathodoluminescence imaging clearly shows the presence of small crystals embedded in/or between larger crystallites of Cs4PbBr6 and they emit around 520 nm. EDX shows that the smaller crystal inclusions have a Pb : Br ratio that is approximately 2 times higher, confirming the CsPbBr3 phase, which has the expected size-dependent shift to shorter wavelengths (about 528 to 515 nm). These studies make significant inroads into understanding these lead halide perovskites for their use in a variety of optoelectronic and photovoltaic applications.

Graphical abstract: On the origins of the green luminescence in the “zero-dimensional perovskite” Cs4PbBr6: conclusive results from cathodoluminescence imaging

Article information

Article type
Paper
Submitted
16 Nov 2018
Accepted
29 Jan 2019
First published
30 Jan 2019

Nanoscale, 2019,11, 3925-3932

On the origins of the green luminescence in the “zero-dimensional perovskite” Cs4PbBr6: conclusive results from cathodoluminescence imaging

N. Riesen, M. Lockrey, K. Badek and H. Riesen, Nanoscale, 2019, 11, 3925 DOI: 10.1039/C8NR09255A

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