4.8 Article

Giant enhancement of photoluminescence quantum yield in 2D perovskite thin microplates by graphene encapsulation

Journal

NANO RESEARCH
Volume 14, Issue 6, Pages 1980-1984

Publisher

TSINGHUA UNIV PRESS
DOI: 10.1007/s12274-020-2971-x

Keywords

two-dimensional perovskite; photoluminescence; quantum yield; quantum confinement; surface depletion field

Funding

  1. National Basic Research Program of China [2018YFA0704403]
  2. National Natural Science Foundation of China [61674060]
  3. Innovation Fund of WNLO
  4. Testing Center of Huazhong University of Science and Technology

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The optoelectronic performances of layered materials are highly dependent on sample thickness, especially when the size is reduced to nanometer scale where surface effects become significant. In this study, it was found that the photoluminescence quantum yield of 2D perovskite microplates can be greatly enhanced when encapsulated by graphene, providing a cost-effective approach to improve luminescence efficiency.
The optoelectronic performances of the layered materials are strongly dependent on the thickness of the samples due to the surface effect. As the size of the samples decreases to few nanometers, the surface depletion field and surface defect density are prominent arising from the large surface to volume ratio. For instance, thin two-dimensional (2D) organic-inorganic hybrid perovskite microplates usually exhibit a rather low photoluminescence quantum yield (PLQY), owning to the strong surface effect. Here, we report that the PLQY can be enhanced as large as 28 times in (iso-BA)(2)Pbl(4)(BA = C4H9NH3) 2D perovskite thin microplates encapsulated by graphene, resulting in that the PLQY is more than 18% for the microplate with a thickness of 6.7 nm at 78 K. As the thickness of the 2D perovskite microplate increases, the enhancement is gradually reduced and finally vanishes. This observation is in striking contrast to that in monolayer transition metal dichalcogenides (TMDs), when the PLQY is quenched by covering a layer of graphene due to the efficient charge transfer. The enhancement of PLQY in 2D perovskites can be mainly ascribed to the reduced quantum confined Stark effect (QCSE) due to the reduced surface depletion field after covering graphene flake, resulting in the enhanced radiative recombination efficiency. Our findings provide a cost-effective approach to enhance the luminescence, which may pave the way toward high performance light emitting devices based on 2D perovskites.

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