Two-dimensional (2D) hybrid organic-inorganic perovskites with tunable structures and strongly bound excitons are desirable for optoelectronic applications. Exciton transport and annihilation are two key processes in determining device efficiencies; however, a thorough understanding of these processes is hindered by that annihilation rates are often convoluted with exciton diffusion constants. Here we employ transient absorption microscopy to disentangle quantum-well-thickness-dependent exciton diffusion and annihilation in 2D perovskites, reveling the key role of electron-hole interactions and dielectric screening. Exciton diffusion constant is found to increase with quantum-well thickness, ranging from 0.06 ± 0.03 cm2s-1 to 0.34 ± 0.03 cm2s-1, which leads to long-range exciton diffusion over hundreds of nanometers. Exciton annihilation is not limited by diffusion and decreases over an order of magnitude as quantum well thickness increases from n = 1 to 5, resulting from enhanced dielectric screening. Exciton annihilation rates are between10-3 and 10-2 cm2s-1, more than one order of magnitude lower than those of monolayer transition metal dichalcogenides. These results unveil the unique attributes 2D perovskites possess as an exciting class of optoelectronic materials, including strongly bound excitons, long-range transport, and slow annihilation.

Long-range exciton transport and slow annihilation in two-dimensional hybrid perovskites

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.