Clearly Discriminate the Continuum Band and Exciton State of the Hybrid Lead Bromide Perovskite

TL;DR

This study clarifies the electronic structure of hybrid lead bromide perovskites by directly observing free carrier emissions and distinguishing exciton states from the continuum band, resolving longstanding controversies.

Contribution

It introduces a method to directly discriminate between continuum band and exciton states in hybrid perovskites, advancing understanding of their electronic mechanisms.

Findings

Direct observation of free carrier emissions

Dual-peak emissions are excitonic in origin

Excitons have giant binding energies and high phase stability

Abstract

Electronic states of the hybrid perovskite enable their promising applications as distinctive optoelectronic materials. The understanding of their electronic structures and charge characters remains highly controversial. The electronic mechanism such as reabsorption, Urbach tail and indirect band for interpreting dual-peak emissions is one of the controversial focuses. Herein, we report that through heterojunction enhanced exciton dissociation and global tracing of multiple radiative electronic states across wide temperature regions, we have succeeded in directly observing free carrier emissions from the hybrid lead bromide perovskite and clearly discriminating the direct continuum band and exciton states. The widely-concerned dual-peak emissions are clarified to be excitonic, arising from two types of exciton states of the perovskite. These excitons possess giant binding energies and superior phase stability compared to conventional inorganic semiconductors, providing important implications for exploiting the excitonic mechanism for realizing novel optoelectronic applications.