Brightening of dark excitons in 2D perovskites.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34757785.
- Also identified by DOI 10.1126/sciadv.abk0904 and PMC identifier 8580304.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Optically inactive dark exciton states play an important role in light emission processes in semiconductors because they provide an efficient nonradiative recombination channel. Understanding the exciton fine structure in materials with potential applications in light-emitting devices is therefore critical. Here, we investigate the exciton fine structure in the family of two-dimensional (2D) perovskites (PEA)<sub>2</sub>SnI<sub>4</sub>, (PEA)<sub>2</sub>PbI<sub>4</sub>, and (PEA)<sub>2</sub>PbBr<sub>4</sub>. In-plane magnetic field mixes the bright and dark exciton states, brightening the otherwise optically inactive dark exciton. The bright-dark splitting increases with increasing exciton binding energy. Hot photoluminescence is observed, indicative of a non-Boltzmann distribution of the bright-dark exciton populations. We attribute this to the phonon bottleneck, which results from the weak exciton–acoustic phonon coupling in soft 2D perovskites. Hot photoluminescence is responsible for the strong emission observed in these materials, despite the substantial bright-dark exciton splitting.