Tuning optoelectronic response of lateral core-alloyed crown nanoplatelets: type-II CdSe–CdSe_1−x Te _x

Abstract

We present a theoretical study showing that the exciton emission in the CdSe–CdSe1−x Te x core-alloyed crown heterostructure results from the tunable quasi-type II to pure type II behavior by adjusting the Te to Se ratio. We suggest that the direct crown exciton or interface indirect exciton or a dual emission can be tuned due to the altered conduction band offset. We also found that these different emissions are red-shifted with increasing the nanoplatelets (NPLs) monolayer (ML) thickness due to the quantum confinement effect. The double exciton emission develops caused by the band bowing effect occurring in the alloyed crown. The band bowing is originated from the difference between the bonding nature of the Se and Te orbitals with the Cd orbitals in the conduction band edge states. We also found that the band bowing is sensitive on the alloyed-crown ML thickness and the in-plane strain due to hybridization magnitude between the cation (Cd) and anion (Se, Te). Our results are in accord with the available experimental data. We propose the CdSe–CdSe1−x Te x core-alloyed crown NPLs as a promising contender for the near-infrared-emitting heterostructures preparation used for light-harvesting applications.

2D II–VI Semiconductor Nanoplatelets: From Material Synthesis to Optoelectronic Integration

“…These NPLs are called core/crown 47 or core/wings. 48 Various heterostructures, including CdSe/CdS, 47,48 inverted CdS/ CdSe, 153 CdSe/CdSSe, CdSe/CdSeTe, 58,59,154 CdSe/CdTe have been achieved. 21,155 More recently, core/crown/crown heterostructures have also been reported.…”

“…These NPLs are called core/crown or core/wings . Various heterostructures, including CdSe/CdS, , inverted CdS/CdSe, CdSe/CdSSe, CdSe/CdSeTe, ,, CdSe/CdTe have been achieved. , More recently, core/crown/crown heterostructures have also been reported . These heterostructures are developed under conditions comparable to those used for the nucleation of NPLs.…”

High External Quantum Efficiency Light-Emitting Diodes Enabled by Advanced Heterostructures of Type-II Nanoplatelets

“…25,27 In addition, a quasi-type-II structure was used in a few studies by employing an alloyed CdSe x Te 1−x crown to obtain enhanced optical properties such as improved QY and emission tunability compared to pristine CdSe/CdTe NPLs. 18,27 Cd-based NPL-LEDs offer excellent prospects for display and lighting technologies owing to their attractive properties inherent from their Cd-containing NPLs such as high external quantum efficiency (EQE), high color purity, and low power consumption, in addition to their solution processability potentially enabling low-cost fabrication and flexibility. 16,28−30 In the literature, type-I NPLs have been widely investigated for LEDs applications.…”

Synthesis of CdSe and CdSe/ZnS Quantum Dots with Tunable Crystal Structure and Photoluminescent Properties

“…Besides the ligand, surface passivation by constructing a core–shell structure is equally important to the fluorescence properties. QDs with an alloyed shell usually exhibit a wide emission peak (>100 meV) because the gradient interface between the core and the shell has a weak electron confinement [ 26 , 27 ]. Therefore, core–shells with a heterostructure are more suitable for laser application.…”