Efficient Band-Edge Emission from Indirect Bandgap Semiconductor Quantum Dots upon Shell Engineering
Jingwen Zhai, Tieshuan Dong, Yamei Zhou, Jingjing Min, Yuli Yan, Christos S. Garoufalis, Sotirios Baskoutas, Dangdang Xu, Zaiping Zeng
Abstract
Environmentally friendly colloidal quantum dots (QDs) of groups III–V are in high demand for next-generation high-performance light-emitting devices for display and lighting, yet many of them (e.g., GaP) suffer from inefficient band-edge emission due to the indirect bandgap nature of their parent materials. Herein, we theoretically demonstrate that efficient band-edge emission can be activated at a critical tensile strain γ c enabled by the capping shell when forming a core/shell architecture. Before γ c is reached, the emission edge is dominated by dense low-intensity exciton states with a vanishing oscillator strength and a long radiative lifetime. After γ c is crossed, the emission edge is dominated by high-intensity bright exciton states with a large oscillator strength and a radiative lifetime that is shorter by a few orders of magnitude. This work provides a novel strategy for realizing efficient band-edge emission of indirect semiconductor QDs via shell engineering, which is potentially implemented employing the well-established colloidal QD synthesis technique.