Energy-Level Structure and Band Alignment in InP/ZnSe Core/Shell Quantum Dots.

Dobromił Respekta,Pieter Schiettecatte, Luca Giordano, Norick De Vlamynck,Pieter Geiregat, Juan Ignacio Climente,Zeger Hens

ACS nano（2025）

Departament de Química Física i Analítica

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Abstract

Quantum dots (QDs) feature a sequence of discrete electron and hole energy levels that are often characterized by the envelope symmetry of the electron orbitals. Furthermore, these orbitals exhibit a specific localization in the case of core/shell QDs, extended across the entire QD or restricted to either the core or the shell, depending on the band alignment. Here, we investigate the energy-level alignment in InP/ZnSe core/shell QDs. In agreement with predictions based on k·p calculations, we show that optical transitions in these QDs follow well-defined, mutually exclusive selection rules in 1-photon and 2-photon absorption that can be related to the envelope symmetry of the orbitals involved. In addition, we argue based on a combination of the transient absorption spectrum and the k·p calculations that the lower energy transitions in InP/ZnSe QDs excite electrons from different valence band (VB) levels to the lowest conduction band level. We use this insight to align the InP- and ZnSe-based energy levels and conclude that the VB offset exceeds the natural band offset between InP and ZnSe. Applying this procedure to QDs with decreasing InP core sizes shows a progressive reduction of the offset between the core and shell VB levels. The enhanced tailing of the hole wave function into the ZnSe shell for smaller InP cores can affect the stability of such QDs.

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【要点】：研究InP/ZnSe核壳量子点的能级结构和能带对齐情况，发现其遵循特定的选择定则，并与轨道包络对称性相关，同时提出价带偏移量超过InP与ZnSe自然能带偏移的观点。

【方法】：结合k·p计算和瞬态吸收光谱分析量子点的能级排列。

【实验】：通过分析不同InP核心尺寸的量子点，发现随着InP核心尺寸的减小，核与壳价带能级偏移量逐渐减小，影响量子点的稳定性。数据集名称在文中未明确提及。