"Mechanism for Broadband White-Light Emission from Two-Dimensional (110) Hybrid Perovskites"

Te Hu: Matthew D. Smith, Emma R. Dohner, Meng-Ju Sher, Xiaoxi Wu, M. Tuan Trinh, Alan Fisher, Jeff Corbett, X.-Y. Zhu, Hemamala I. Karunadasa, Aaron M. Lindenberg; Journal of Physical Chemistry Letters, 06/01/2016.

Additional Authors: Matthew D. Smith, Emma R. Dohner, Meng-Ju Sher, Xiaoxi Wu, M. Tuan Trinh, Alan Fisher, Jeff Corbett, X.-Y. Zhu, Hemamala I. Karunadasa, Aaron M. Lindenberg

Abstract:

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 = N1-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.