Interlayer Determined Photoluminescence Excitation Properties of Cs-Rich and Pb-Rich Cs4PbBr6 Samples

Here, we fabricated Cs-rich and Pb-rich Cs4PbBr6 samples with green photoluminescence emission and investigated the difference between them. Both Cs-rich and Pb-rich Cs4PbBr6 samples show strong green emissions at about 520 nm; however, the photoluminescence excitation properties of the green emission are greatly different from each other in the ultraviolet region. The photoluminescence excitation spectra of the Cs-rich sample have a broad excitation band from 334 to 500 nm. In comparison, the Pb-rich sample has two additional excitation bands of 250–300 and 324–334 nm. By correlating the experimental data with the theoretical calculations, the green photoluminescence emission can be attributed to the embedded CsPbBr3 nanocrystals, and the interlayer between Cs4PbBr6 and CsPbBr3 nanocrystals plays an important role in determining their photoluminescence excitation properties. It was proposed that the existence of the CsBr interlayer between the Cs4PbBr6 matrix and embedded CsPbBr3 nanocrystals block the electron transfer of excited Cs4PbBr6 and induce photoluminesence quenching under excitation of 250–300 nm.