Band Gap Renormalization at Different Symmetry Points in Perovskites
Using ultrafast broad-band transient absorption (TA) spectroscopy of photoexcited MAPbBr3 thin films with probe continua in the visible and the mid- to deep-ultraviolet (UV) ranges, we capture the ultrafast renormalization at the fundamental gap at the R symmetry point of the Brillouin zone (BZ) and a higher energy gap at the M symmetry point. Advanced global lifetime analysis and lifetime density distribution analysis are applied to extract quantitative information. Our work confirms the similarity of the response at both high-symmetry points, which indicates a band edge renormalization that rises within the instrument response function (IRF, similar to 250 fs) and decays in ca. 400-600 fs, undergoing an energy red shift of 90-150 meV. The reported time scale corresponds to the decay of free carriers into neutral excitons. The ability to monitor different high-symmetry points in photoexcited perovskites opens exciting prospects for the characterization of a large class of materials and for photonic applications.
WOS:001227310700001
2024-05-17
REVIEWED
EPFL
Funder | Grant Number |
Horizon 2020 Framework Programme | 695197 |
European Research Council | |
Swiss NSF via the NCCR:MUST | |
King Abdullah University of Science and Technology (KAUST) | P0042930 |
Hong Kong Polytechnic University | PolyU25300823 |
Research Grants Council of the Hong Kong Special Administrative Region, China | 101095012 |
ERC | |