Signatures of Polaron Dynamics in Photoexcited MAPbBr3 by Infrared Spectroscopy

Valentina Carpenella; Claudia Fasolato; Diego Di Girolamo; Jessica Barichello; Fabio Matteocci; Caterina Petrillo; Danilo Dini; Alessandro Nucara

doi:10.1021/acs.jpcc.3c03668

Signatures of Polaron Dynamics in Photoexcited MAPbBr₃ by Infrared Spectroscopy

J Phys Chem C Nanomater Interfaces. 2023 Nov 3;127(45):22097-22104. doi: 10.1021/acs.jpcc.3c03668. eCollection 2023 Nov 16.

Authors

Valentina Carpenella¹, Claudia Fasolato², Diego Di Girolamo³, Jessica Barichello⁴, Fabio Matteocci⁴, Caterina Petrillo⁵, Danilo Dini³, Alessandro Nucara⁶

Affiliations

¹ Department of Sciences, University of Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy.
² CNR-ISC, Istituto dei Sistemi Complessi, c/o Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy.
³ Department of Chemistry, Sapienza University of Rome, P.le A. Moro 5, 00185 Rome, Italy.
⁴ CHOSE, Department of Electronic Engineering, University of Rome Tor Vergata, Rome 00133 Italy.
⁵ Department of Physics and Geology, University of Perugia, Via A. Pascoli, 06123 Perugia, Italy.
⁶ CNR-SPIN and Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.

Abstract

Hybrid organic-inorganic perovskites (HOIPs) have attracted considerable attention in the past years as photoactive materials for low-cost, high-performance photovoltaics. Polaron formation through electron-phonon coupling has been recognized as the leading mechanism governing charge carrier transport and recombination in HOIPs. In this work, two types of MAPbBr₃ film samples deposited on different substrates (transparent insulating SrTiO₃ and a heterostructure mimicking a functioning photovoltaic cell) were photoexcited with above-bandgap radiation at 450 nm, and the effects of illumination on the sample were analyzed in the infrared region. The infrared absorbance detected at different powers of the photoexciting laser allowed us to obtain an estimate of the characteristic decay time of photoexcited polaron population of the order of 100-1000 ns. When focusing on the absorption features of the MA molecular cation in the region of the NH stretching modes, we observed the influence of hydrogen bonding and the effect of the polaron dynamics on the cation reorientation.