Impact of A-Site Cations on Fluorescence Quenching in Organic–Inorganic Hybrid Perovskite Materials

Abstract

Organic–inorganic hybrid perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology. To improve the luminescence efficiency, it is mandatory to understand the luminescence mechanism in organic–inorganic hybrid perovskites. In this study, organic–inorganic hybrid perovskite films with different A-site components including CH3NH3 + (MA+), NH2CHNH2 + (FA+), CH3CH2NH3 + (EA+), and CH3CH2CH2NH3 + (PA+) were prepared to study the mechanism of fluorescence quenching related to A-site organic cations. An interesting phenomenon is that a EABr:PbBr2 film with two carbons emits only weak light, while a MABr:PbBr2 film with only one carbon, a PABr:PbBr2 film with three carbons, and a FABr:PbBr2 film with two nitrogens at both ends emit bright light. The calculated results by density functional theory show that the partial charge densities for EAPbBr3 and EA4Pb3Br10 are very localized, which means that they can capture electrons or holes and become nonradiative recombination centers. Meanwhile, the evident changes in the Pb–Br–Pb bond lengths, small free volume, and the strong CH3 vibration indicate that EA+ is more likely to collide with the PbBr3 – cavity formed by eight adjacent corner-sharing PbBr6 4– octahedra, enhancing electron–phonon coupling, which leads to serious fluorescence quenching.