Perovskites with narrow quantum-wells distribution and thermally activated energy funneling for sky-blue light-emitting diodes

Abstract

Reduced dimensional perovskite light-emitting diodes have undergone rapid development in recent years, leading to improved device efficiency surpassing their three-dimensional counterparts. However, its fundamental carrier characteristics have not been thoroughly investigated. In this study, A-site cation formamidinium (FA) and co-spacer cation isobutylamine (iBA) are incorporated into reduced-dimensional perovskite PEA2Cs3Pb4Br10Cl3 (where PEA is phenylethylammonium), and a more concentrated quantum-wells distribution is observed due to the utilization of co-spacer cations and the interaction between spacer cations and FA+, facilitating enhanced energy funneling process. Additionally, thermally activated energy funneling process is firstly reported which contribute to the thermally activated long-lived delayed photoluminescence. A longer decay signal at emission center can be observed in transient absorption spectrum of the PEA2iBA2Cs2FAPb4Br12Cl3 perovskite film due to the more sufficient energy transfer. Owing to the efficient carrier utilization and reduced defect states, sky-blue perovskite light-emitting diodes are successfully fabricated with peak external quantum efficiency of 12.7 % and high luminance of 4513 cd m−2.