Zero-dimensional metal halides have emerged as a promising class of luminescent materials, attracting significant interest due to their unique electronic structures and fascinating optical characteristics. The photoluminescence (PL) properties of inorganic ternary Cs₃Er_xYb_1-xCl₆ nanocrystals (NCs) were investigated. These alloyed NCs emit dual-band near-infrared (NIR) PL, featuring a sharp NIR-II emission at 1543 nm alongside an NIR-I emission around 987 nm, which originate from the rare earth Er³⁺ and Yb³⁺ ions, respectively. Cs₃Er_0.06Yb_0.94Cl₆ NCs exhibit efficient NIR-II PL with a quantum yield of 2.7% and a lifetime of 157 µs. The enhanced NIR-II PL can be attributed to highly localized excitons, fast energy transfer from Yb³⁺ to Er³⁺ ions and passivation of nonradiative defect states in the Er-Yb alloyed NCs. Given their good penetrability of the NIR-II PL from Er³⁺ ions, a single-component NIR phosphor-converted light-emitting diode (pc-LED) fabricated using Cs₃Er_0.06Yb_0.94Cl₆ NCs demonstrates their potential for future applications in optical communication.

Bandgap engineering of semiconductor nanowires or nanoribbons (NRs) offers a promising material foundation for multifunctional integrated optoelectronic devices and circuits. Among these materials, all-inorganic halide perovskites have emerged as a leading candidate for next-generation photoelectronic applications due to their outstanding optoelectronic properties. In this work, we report the direct synthesis of high-quality bandgap gradient lead halide perovskite (CsPbCl_3−3xBr_3x and CsPbBr_3−3xI_3x (x = 0–1)) NRs using a magnetic-pulling source-moving chemical-vapor-deposition (CVD) method. Microstructural characterizations reveal that these as-grown NRs possess high-quality single crystalline structures with continuously tunable compositions. The photoluminescence emissions of these perovskite NRs can be finely tuned across the entire visible spectrum (417–702 nm). Furthermore, photodetectors based on these perovskite NRs demonstrate exceptional photoelectric performance, including a high I_ON/I_OFF ratio (10⁴), superior responsivity (37.5 A/W), and remarkable detectivity (2.81 × 10¹³ Jones). A spatially resolved imaging sensor based on these perovskite NRs is also demonstrated, indicating promising applications in photoelectronic imaging circuits. These bandgap-tunable perovskite NRs provide a versatile materials platform for future integrated devices in electronics and optoelectronics.

Colloidal semiconductor quantum dots (QDs) exhibit broadband light absorption, continuously tunable narrowband emission, and high photoluminescence quantum yields. As such, they represent promising materials for use in light-emitting diodes, solar cells, detectors, and lasers. Single-QD spectroscopy can remove the ensemble averaging to reveal the diverse optical properties and exciton dynamics of QD materials at the single-particle level. The results of relevant research can serve as guidelines for materials science community in tailoring the synthesis of QDs to develop novel applications. This paper reviews recent progress in exciton dynamics revealed by single-QD spectroscopy, focusing on the exciton and multi-exciton dynamics of single colloidal CdSe-based QDs and perovskite QDs. Finally, potential future directions for single-QD spectroscopy and exciton dynamics are briefly considered.

The two frequently observed phenomena, photoluminescence (PL) blinking and quantum-confined Stark effect (QCSE)-induced spectral diffusion, are not conducive to the applications of colloidal quantum dots (QDs). It remains elusive how these two phenomena are linked to each other. Unraveling the potential link between blinking and QCSE could facilitate the adoption of appropriate strategies that can simultaneously suppress both PL blinking and spectral diffusion. In this work, we investigated the blinking mechanism and QCSE of single CdSe/CdS/ZnS QDs in the presence of positive and negative surface charges using single-dot PL spectroscopy. We found that the negative surface charges can simultaneously suppress PL blinking and spectral diffusion of single QDs. On the other hand, the positive surface charges could change the blinking mechanisms of QDs from Auger-blinking to band-edge carrier (BC)-blinking. Two types of QCSE were observed, and a significant QCSE-induced spectral broadening of 5.25 nm was measured, which could be attributed to the hopping of surface charges between different surface-trap sites. Based on these findings, several theoretical models are proposed to explain various phenomena observed.