The vacancy-ordered quadruple perovskite Cs₄CdBi₂Cl₁₂, as a newly-emerging lead-free perovskite system, has attracted great research interest due to its excellent stability and direct band gap. However, the poor luminescence performance limits its application in light-emitting diodes (LEDs) and other fields. Herein, for the first time, an Ag⁺ ion doping strategy was proposed to greatly improve the emission performance of Cs₄CdBi₂Cl₁₂ synthesized by hydrothermal method. Density functional theory calculations combined with experimental results evidence that the weak orange emission from Cs₄CdBi₂Cl₁₂ is attributed to the phonon scattering and energy level crossing due to the large lattice distortion under excited states. Fortunately, Ag⁺ ion doping breaks the intrinsic crystal field environment of Cs₄CdBi₂Cl₁₂, suppresses the crossover between ground and excited states, and reduces the energy loss in the form of nonradiative recombination. At a critical doping amount of 0.8%, the emission intensity of Cs₄CdBi₂Cl₁₂:Ag⁺ reaches the maximum, about eight times that of the pristine sample. Moreover, the doped Cs₄CdBi₂Cl₁₂ still maintains excellent stability against heat, ultraviolet irradiation, and environmental oxygen/moisture. The above advantages make it possible for this material to be used as solid-state phosphors for white LEDs applications, and the Commission International de I’Eclairage color coordinates of (0.31, 0.34) and high color rendering index of 90.6 were achieved. More importantly, the white LED demonstrates remarkable operation stability in air ambient, showing almost no emission decay after a long working time for 48 h. We believe that this study puts forward an effective ion-doping strategy for emission enhancement of vacancy-ordered quadruple perovskite Cs₄CdBi₂Cl₁₂, highlighting its great potential as efficient emitter compatible for practical applications.

SrZrS₃ is a promising chalcogenide perovskite with unique advantages including high abundance of consisting elements, high chemical stability, strong light absorption above its direct band gap, and excellent carrier transport ability. While unfortunately, due to the lack of breakthroughs in its thin film synthesis technique, its optoelectronic properties are not fully investigated, not to mention the device applications. In this work, large-area and uniform SrZrS₃ thin film (5 cm × 5 cm) was prepared by facile sputtering method, followed by a post-annealing treatment at a high temperature of 1000 °C for 2–12 h under CS₂ atmosphere. All SrZrS₃ samples prepared adopt distorted orthorhombic structure with pnma space group and have high crystallinity. In addition, the band gap of SrZrS₃ thin film is measured to be 2.29 eV, higher than that of the powder form (2.06 eV). Importantly, the light absorption coefficient of SrZrS₃ thin film reaches over 10⁵ cm⁻¹, and the carrier mobility is as high as 106 cm²/(V∙s). The above advantages allow us to use the SrZrS₃ thin film as photoactive layer for photodetector applications. Finally, a symmetrically structured photoconductive detector was fabricated, performing a high responsivity of 8 A/W (405 nm light excitation). These inspiring results promise the glorious application potential of SrZrS₃ thin film in photodetectors, solar cells, and other optoelectronic devices.

Luminescent nanothermometry can precisely and remotely measure the internal temperature of objects at nanoscale precision, which, therefore, has been placed at the forefront of scientific attention. In particular, due to the high photochemical stability, low toxicity, rich working mechanisms, and superior thermometric performance, lanthanide-based ratiometric luminesencent thermometers are finding prevalent uses in integrated electronics and optoelectronics, property analysis of in-situ tracking, biomedical diagnosis and therapy, and wearable e-health monitoring. Despite recent progresses, it remains debate in terms of the underlying temperature-sensing mechanisms, the quantitative characterization of performance, and the reliability of temperature readouts. In this review, we show the origin of thermal response luminescence, rationalize the ratiometric scheme or thermometric mechanisms, delve into the problems in the characterization of thermometric performance, discuss the universal rules for the quantitative comparison, and showcase the cutting-edge design and emerging applications of lanthanide-based ratiometric thermometers. Finally, we cast a look at the challenges and emerging opportunities for further advances in this field.

Multi-photon-pumped lasing based on metal-halide perovskites is promising for nonlinear optics and practical frequency- upconversion devices in integrated photonic systems. However, at present almost all the multi-photon-pumped lasing emissions from perovskite microcavities were limited for two-photon excitation, and also suffered from a compromise in room temperature or low temperature operation conditions. In this study, based on the vapor-phase epitaxial CsPbBr₃ microplatelets with high crystallinity, self-formed high-quality microcavities, and great thermal stability, low-threshold and high-quality factor whispering gallery mode lasing was realized under single-, two-, and three-photon excitation, and the lasing action is very stable under continuous pulsed laser irradiation (~ 3.6 × 10⁷ laser shots). More importantly, the three-photon-pumped lasing can be efficiently sustained at a high temperature of ~ 400 K, and the characteristic temperature was determined to be as high as ~ 152.6 K, indicating the highly temperature-insensitive gain threshold. Note that this is the first report on high-temperature three-photon-pumped lasing on perovskite microcavities. Moreover, an aggressive thermal cycling test (two cycles, 290−400−290 K) was further performed to indicate the stability and repeatability of the multi-photon-pumped lasing characteristics. It can be anticipated that the results obtained represent a significant step toward the temperature-insensitive frequency-upconversion lasing, inspiring the exploitation of advantageous perovskites for novel applications.