Phonon-Assisted Trapping and Re-excitation of Free Carriers and Excitons in Lead Halide Perovskites

Giacomo M. Piana, Christopher G. Bailey, Pavlos G. Lagoudakis

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Despite the advances in solar cells based on lead halide perovskites, the nature of photogenerated charges and trap states within these materials remains unclear. A model describing recombination in CH3NH3PbI3-xClx has been developed that accounts for phonon-assisted free-exciton and free-carrier trapping. We utilize optical spectroscopies and observe significant co-existence of the tetragonal and orthorhombic structural phases at low temperatures. From these measurements, we evaluate the longitudinal-optical phonon energy, exciton binding energy, and temperature-dependent electronic bandgap. We use these parameters to model the temperature- and fluence-dependent time-resolved photoluminescence decays, enabling us to demonstrate how shallow traps from which carriers can be re-excited can account for the delayed recombination in lead halide perovskites. The trap-state density reaches a maximum at the tetragonal to orthorhombic phase transition at ∼140 K, suggesting the formation of disorder-induced trap states, which are shown to dominate the recombination dynamics in CH3NH3PbI3-xClx.

Original languageEnglish
Pages (from-to)19429-19436
Number of pages8
JournalJournal of Physical Chemistry C
Volume123
Issue number32
DOIs
Publication statusPublished - 15 Aug 2019
Externally publishedYes

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