Ultrafast Exciton Transport with a Long Diffusion Length in Layered Perovskites with Organic Cation Functionalization.
ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020;
32:e2004080. [PMID:
33048430 DOI:
10.1002/adma.202004080]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 09/09/2020] [Indexed: 06/11/2023]
Abstract
Layered perovskites have been employed for various optoelectronic devices including solar cells and light-emitting diodes for improved stability, which need exciton transport along both the in-plane and the out-of-plane directions. However, it is not clear yet what determines the exciton transport along the in-plane direction, which is important to understand its impact toward electronic devices. Here, by employing both steady-state and transient photoluminescence mapping, it is found that in-plane exciton diffusivities in layered perovskites are sensitive to both the number of layers and organic cations. Apart from exciton-phonon coupling, the octahedral distortion is revealed to significantly affect the exciton diffusion process, determined by temperature-dependent photoluminescence, light-intensity-dependent time-resolved photoluminescence, and density function theory calculations. A simple fluorine substitution to phenethylammonium for the organic cations to tune the structural rigidity and octahedral distortion yields a record exciton diffusivity of 1.91 cm2 s-1 and a diffusion length of 405 nm along the in-plane direction. This study provides guidance to manipulate exciton diffusion by modifying organic cations in layered perovskites.
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