The realization of colloidal alloy quantum dots (QDs) with narrow spectral linewidths requires minimization of the contributions of inhomogeneous and homogeneous broadening to the ensemble spectrum. Recently, there has been remarkable progress in eliminating the inhomogeneous contribution by controlling the size distribution of the QDs. However, considerable challenges remain in suppressing the homogeneous broadening, in terms of both intrinsic principles and rational synthetic routes. We find that ground-state exciton fine structure splitting and exciton—phonon coupling play a pivotal role in the homogeneous broadening mechanism. Here we demonstrate that the elimination of the lattice mismatch strain by using a coherent strain structure can decrease the light-heavy hole splitting, thus suppressing the asymmetric broadening of the emission on the high energy side. Besides, the improvement of the uniformity of the alloy by using a stepwise ion exchange strategy can weaken the exciton—longitudinal optical (LO)-phonon interactions, further minimizing the homogeneous broadening. As a result, the final alloy QD products exhibit a widely tunable blue emission wavelength (445–470 nm) with the narrowest ensemble photoluminescence full width at half maximum (FWHM) of 10.1–13.5 nm (or 58.4–75.3 meV). Our study provides a potential strategy for other semiconductor nanocrystals with ultranarrow spectral linewidths.

实现具有窄谱线宽的胶体合金量子点 (QD) 需要最小化不均匀和均匀展宽对整体光谱的贡献。最近，通过控制量子点的尺寸分布，在消除不均匀贡献方面取得了显着进展。然而，就内在原理和合理合成路线而言，在抑制均匀展宽方面仍存在相当大的挑战。我们发现基态激子精细结构分裂和激子-声子耦合在均匀展宽机制中起关键作用。在这里，我们证明了通过使用相干应变结构消除晶格失配应变可以减少轻重空穴分裂，从而抑制高能侧发射的不对称展宽。此外，通过使用逐步离子交换策略提高合金的均匀性可以削弱激子-纵向光学（LO）-声子相互作用，进一步最小化均匀展宽。因此，最终合金 QD 产品表现出可广泛调谐的蓝色发射波长（445-470 nm），最窄的半峰全宽（FWHM）为 10.1-13.5 nm（或 58.4-75.3 meV）。我们的研究为其他具有超窄光谱线宽的半导体纳米晶体提供了一种潜在的策略。进一步最小化均匀展宽。因此，最终合金 QD 产品表现出可广泛调谐的蓝色发射波长（445-470 nm），最窄的半峰全宽（FWHM）为 10.1-13.5 nm（或 58.4-75.3 meV）。我们的研究为其他具有超窄光谱线宽的半导体纳米晶体提供了一种潜在的策略。进一步最小化均匀展宽。因此，最终合金 QD 产品表现出可广泛调谐的蓝色发射波长（445-470 nm），最窄的半峰全宽（FWHM）为 10.1-13.5 nm（或 58.4-75.3 meV）。我们的研究为其他具有超窄光谱线宽的半导体纳米晶体提供了一种潜在的策略。