Recent Advances and Perspectives on Colloidal Semiconductor Nanoplatelets for Optoelectronic Applications

Abstract

The strategy of a new generation of light-harvesting systems based on two-dimensional (2D) colloidal semiconductor nanoplatelets (NPLs) is an emerging field of research owing to the strong confinement in one direction, narrow emission, large exciton binding energy, and large absorption cross-section. In this Perspective, we provide fundamental insights into the ultrafast dynamics and luminescent properties of 2D semiconductor NPLs and their heterostructures. The variation of hot carrier cooling dynamics with changing the thickness of monolayers of CdSe NPLs is evident. Slow exciton recombination of 2D NPLs is reported in the presence of electron and hole acceptor molecules, indicating efficient charge separation which eventually controls the device performance. We envision the possibility of designing 2D NPLs heterostructures in combination with metal clusters, perovskite nanocrystals, and graphene oxide for photodetector, light-emitting diodes, photocatalysis, electroluminescence, and photovoltaics applications by controlling their charge transfer dynamics. The future perspective of this research field with promising areas is discussed.

Cyan Emission in Two-Dimensional Colloidal Cs2CdCl4:Sb3+Ruddlesden–Popper Phase Nanoplatelets

“…Despite progress in the formation of bulk materials, the use of RP phases as an optoelectronic material is still hampered by the difficulty to obtain phase-pure films that exhibit a spatially homogeneous composition and crystal structure . In this regard, the use of presynthesized colloidal nanocrystals − or nanoplatelets as starting materials is a promising alternative. − Even so, few studies have addressed the formation of RP phases as colloidal nanocrystals. To the best of our knowledge, only the formation of Cs 2 PbCl 2 I 2 and Cs 2 PbCl 2 I 2 :Mn has been reported in literature. − In more detail, Cs 2 PbCl 2 I 2 exhibited a rather weak blue emission, while Mn 2+ doping resulted in an intense orange emission (PLQY of 16%).…”

Comparison between trion and exciton electronic properties in CdSe and PbS nanoplatelets

“…The outstanding optical features of semiconductor colloidal nanoplatelets (NPLs) makes them a broad target of study and application in devices. [1][2][3][4] As compared to colloidal quantum dots, the quasi-2D nature of NPLs conveys several distinct properties of interest, including precisely controllable thickness -which enables narrow emission linewidths-, large absorption cross-sections and bright luminescence resulting from the giant oscillator strength effect. [2][3][4] Several efforts have been carried out in synthesis methods to control the morphology, dimensions and composition, as well as in characterization of the subsequent optoelectronic properties.…”

“…[1][2][3][4] As compared to colloidal quantum dots, the quasi-2D nature of NPLs conveys several distinct properties of interest, including precisely controllable thickness -which enables narrow emission linewidths-, large absorption cross-sections and bright luminescence resulting from the giant oscillator strength effect. [2][3][4] Several efforts have been carried out in synthesis methods to control the morphology, dimensions and composition, as well as in characterization of the subsequent optoelectronic properties. [4][5][6][7] In parallel, theoretical models have been developed to understand the underlying electronic structure.…”

Simultaneous Ligand and Cation Exchange of Colloidal CdSe Nanoplatelets toward PbSe Nanoplatelets for Application in Photodetectors

“…Other characteristics, such as large absorption coefficients 11,12 and reduced Auger recombination rates, 13 qualify this class of materials as promising candidates for various applications in optoelectronics, sensing, and as colloidal counterparts to quantum wells for fundamental research purposes. 14,15 Currently, the portfolio of ultrathin quasi-2D NCs available via a direct synthesis is still limited to a few compounds, but using cation exchange (CE) reactions to exploit easily prepared NCs as general anion host lattices is a concept that gained traction in recent years. 16,17 Beyond the preparation of new materials, CE also allows the synthesis of high-quality III−V NCs, for which the molecular precursors usually decompose rapidly at lower temperatures, which hinders the successful application of typical hot-injection protocols.…”