Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)
Publication date: 4th October 2020
Colloidal nanoplatelets (NPLs) have become a promising class of semiconductor nanocrystals (NCs) for optoelectronic applications with their distinctly different optical characteristics [1]. They exhibit narrow emission linewidth, large absorption cross-section, giant oscillator strength, and suppressed Auger recombination. However, the first examples of core/shell NPLs synthesized by using a colloidal atomic layer deposition (c-ALD) approach suffered from the low photoluminescence quantum yields (PLQY), decreased crystallinity, and limited stability. Here, to overcome this issue, we demonstrate a high-temperature shell growth approach that enables the synthesis of NPLs with controlled shell composition [2]. Our proposed CdSe quantum wells with a graded shell, which is composed of CdS buffer interlayer and CdxZn1-xS gradient shell, exhibit highly bright emission (PLQY up to 89%) in the red spectral region (634-648 nm) with a narrow emission linewidth (down to 21 nm). With the smooth confinement potential of graded shell NPLs, hence further suppressing Auger recombination, we obtained a low threshold amplified spontaneous emission (~40 µJ/cm2) under nanosecond laser excitation. We also investigated the electroluminescent performance of graded shell NPLs in solution-processed light-emitting diodes (LEDs). Our NPL-LEDs showed a very high external quantum efficiency (EQE) value of 9.92% with high brightness up to ~46000 cd/m2 at 650 nm. These findings show that by carefully designing heterostructures of anisotropically shaped colloidal NPLs, we could obtain highly efficient NPLs with enhanced optical properties to realize their superior performance in optoelectronic applications, overcoming the limitations of the spherically shaped NCs.
M.K and Y.K. acknowledge financial support from the Swiss Federal Commission for Technology and Innovation (CTINo. 25493.3) and the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant No. 798697.
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