Solution-processed two-dimensional nanoplatelets (NPLs)
allowing
lateral growth of a shell (crown) by not affecting the pure confinement
in the vertical direction provide unprecedented opportunities for
designing heterostructures for light-emitting and -harvesting applications.
Here, we present a pathway for designing and synthesizing colloidal
type-II core/(multi-)crown hetero-NPLs and investigate their optical
properties. Stoke’s shifted broad photoluminescence (PL) emission
and long PL lifetime (∼few 100 ns) together with our wavefunction
calculations confirm the type-II electronic structure in the synthesized
CdS/CdSe1–xTexcore/crown hetero-NPLs. In addition, we experimentally obtained
the band-offsets between CdS, CdTe, and CdSe in these NPLs. These
results helped us designing hetero-NPLs with near-unity PL quantum
yield in the CdSe/CdSe1–xTex/CdSe/CdS core/multicrown architecture. These
core/multicrown hetero-NPLs have two type-II interfaces unlike traditional
type-II NPLs having only one and possess a CdS ending layer for passivation
and efficient suppression of stacking required for optoelectronic
applications. The light-emitting diode (LED) obtained using multicrown
hetero-NPLs exhibits a maximum luminance of 36,612 cd/m2and external quantum efficiency of 9.3%, which outcompetes the previous
best results from type-II NPL-based LEDs. These findings may enable
designs of future advanced heterostructures of NPLs which are anticipated
to show desirable results, especially for LED and lasing platforms.