Details

Autor(en) / Beteiligte

• He, Xing
• Tailor, Naveen Kumar
• Satapathi, Soumitra
• Brgoch, Jakoah
• Yang, Ding‐Shyue

Titel

Strong Coupling of Self‐Trapped Excitons to Acoustic Phonons in Bismuth Perovskite Cs3Bi2I9

Ist Teil von

• Advanced optical materials, 2024-03, Vol.12 (8), p.n/a

Ort / Verlag

Weinheim: Wiley Subscription Services, Inc

Erscheinungsjahr

2024

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• To assess the potential optoelectronic applications of metal‐halide perovskites, it is critical to have a detailed understanding of the nature and dynamics of interactions between carriers and the polar lattices. Here, the electronic and structural dynamics of bismuth‐based perovskite Cs3Bi2I9 are revealed by transient reflectivity and ultrafast electron diffraction. A cross‐examination of these results combined with theoretical analyses allows the identification of the major carrier–phonon coupling mechanism and the associated time scales. It is found that carriers photoinjected into Cs3Bi2I9 form self‐trapped excitons on an ultrafast time scale. However, they retain most of their energy, and their coupling to Fröhlich‐type optical phonons is limited at early times. Instead, the long‐lived excitons exert an electronic stress via deformation potential and develop a prominent, sustaining strain field as coherent acoustic phonons in 10 ps. From sub‐ps to ns and beyond, a similar extent of the atomic displacements is found throughout the different stages of structural distortions, from limited local modulations to a coherent strain field to the Debye–Waller random atomic motions on longer times. The current results suggest the potential use of bismuth‐based perovskites for applications other than photovoltaics to take advantage of the carriers’ stronger self‐trapping and long lifetimes. Using optical transient reflectivity and ultrafast electron diffraction, a cross‐examination of photoinduced electronic and structural dynamics of Cs3Bi2I9, a quasi‐zero‐dimensional bismuth‐halide perovskite, reveals the ultrafast formation of self‐trapped excitons and their unexpectedly long lifetime on the sub‐ns scale, the carriers' limited coupling to optical phonons, and their significant coupling to acoustic phonons, prior to energy thermalization and randomized atomic motions.