Gradient Alloy CdSe/CdZnS Nanorods as Polarized Room-Temperature Single-Photon Sources

Colloidal semiconductor nanorods (NRs) are promising room-temperature single-photon sources because of their solution processability, tunable optical properties, and intrinsically linearly polarized emission. However, simultaneously achieving high photoluminescence quantum yield (PLQY), strong polarization, and high-purity single-photon emission remains challenging in conventional binary-shell NRs due to the competing requirements of exciton confinement and core/shell lattice-strain management. Here, we report CdSe/CdZnS gradient alloy core/shell NRs with tunable aspect ratios to address these issues. The gradient alloy shell provides a smooth lattice transition, reducing interfacial strain while maintaining effective exciton confinement. At an aspect ratio of 3.8, the NRs achieve a near-unity PLQY, a high linear polarization (0.76), fully suppressed blinking, and excellent single-photon purity [g2(0) = 0.068]. Increasing the aspect ratio to 13 reduces the PLQY and enhances blinking, with power-law analysis revealing aspect-ratio-dependent on/off-state dynamics. These results demonstrate the potential of alloy-shell NRs as high-brightness, room-temperature single-photon emitters.