Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume 7, Issue 12, Pages 2258-2263Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.6b00793
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Funding
- Precourt Institute for Energy at Stanford University
- Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- Alfred P. Sloan Fellowship
- Stanford Terman Fellowship
- NSF [DGE-114747]
- Global Climate and Energy Project
- U.S. Air Force Office of Scientific Research grant [FA9550-14-1-0381]
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The recently discovered phenomenon of broadband white-light emission at room temperature in the (110) two-dimensional organic-inorganic perovskite (N-MEDA)[PbBr4] (N-MEDA = N-1-methylethane-1,2-diammonium) is promising for applications in solid-state lighting. However, the spectral broadening mechanism and, in particular, the processes and dynamics associated with the emissive species are still unclear. Herein, we apply a suite of ultrafast spectroscopic probes to measure the primary events directly following photoexcitation, which allows us to resolve the evolution of light-induced emissive states associated with white-light emission at femtosecond resolution. Terahertz spectra show fast free carrier trapping and transient absorption spectra show the formation of self-trapped excitons on femtosecond time-scales. Emission-wavelength-dependent dynamics of the self-trapped exciton luminescence are observed, indicative of an energy distribution of photogenerated emissive states in the perovskite. Our results are consistent with photogenerated carriers self-trapped in a deformable lattice due to strong electron-phonon coupling, where permanent lattice defects and correlated self-trapped states lend further inhomogeneity to the excited-state potential energy surface.
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