InP Quantum Dots with a Strain-Engineered Gradient Shell for Enhanced Optical Performance and Stability

InP quantum dots have emerged as a promising ecofriendly alternative to cadmium-based QDs for next-generation display applications. However, red-emitting InP QDs synthesized via aminophosphine precursors still suffer from broad emission spectra and limited stability. In this study, we present a strain-engineered InP/ZnSe/ZnSe_xS_1-x/ZnS QD structure featuring a gradient alloyed ZnSe_xS_1-x shell that effectively mitigates lattice mismatch, reduces strain accumulation, and enhances shell uniformity. Through systematic analysis, we elucidate the strain distribution profiles across different shell architectures and the corresponding defect types induced by strain. This approach enables the controlled growth of a thick ZnS shell, improving passivation and minimizing nonradiative recombination. As a result, the optimized QDs exhibit a narrow full width at half-maximum of 45 nm, a high photoluminescence quantum yield of ≥80%, and significantly enhanced photochemical stability. This work highlights the critical role of strain management in achieving high-performance InP QDs for practical applications.