Interband and Surface‐Influenced Photophysical Processes in CH3NH3PbBr3 Perovskites

• Published in: Advanced photonics research Vol. 3; no. 1
• Main Authors: Cao, Lu, Wang, Jie, Rao, Jia-Rui, Ma, Guang-Zhe, Gao, Min, Shi, Dong
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 01.01.2022; Wiley-VCH
• Subjects: Crystallization; excited phase evolution; exciton; local confinement; Semiconductors; Single crystals; Sommerfeld factor; Thin films; Urbach rule
• ISSN: 2699-9293; 2699-9293
• DOI: 10.1002/adpr.202100198

Metal halide perovskites (MHPs) are attracting ever‐growing interest across diverse optoelectronic subdisciplines. Yet, the physical mechanism underlying photoexcitation and subsequent photocarrier dynamics remains poorly understood, due to the apparent spectroscopic diversities observed for any certain MHP. Here, diverse spectroscopic characteristics, including static spectral line‐shapes and time‐resolved photoluminescence (TRPL) traces shown by polycrystalline versus single‐crystalline CH3NH3PbBr3 perovskites, are restudied. Key photophysical merits, including exciton binding energy (EB), Sommerfeld factor (ξ), and Urbach energy (EU) that account for the diversities, are discussed within the established framework of semiconductor optics. The value of ξ, which increases with EB, determines how much the interband absorption is enhanced beyond that expected for free carriers. The intrinsic band‐edge luminescence is identified, with its asymmetric spectral line‐shape linked to EU via the van Roosbroeck–Shockley relation. Excited phase evolution, accompanied by rapid electron–hole (e–h) pairs dissociation and subsequent occurrence of e–h plasma, is indicated by the two‐stage TRPL traces that are only observable for high‐quality single crystals. With all the spectroscopic analysis and interpretations rooted in the established semiconductor optical theorems, the mechanistic merits revealed in this study are informative for plausible identification between the interband and excitonic photophysical processes of MHPs. The physical mechanism that underlies and controls the spectroscopic responses of one of the most studied prototypical metal halide perovskites, CH3NH3PbBr3, is revealed. The intrinsic band‐edge luminescence from the imperfection‐free crystal lattice bulk is identified. Excited phase evolution accompanied by rapid electron–hole (e–h) pair dissociation and subsequent formation of e–h plasma within the optically excited CH3NH3PbBr3 single‐crystal bulk is demonstrated.