准二维Ruddlesden?Popper（R?P）卤化物钙钛矿具有优越的光电特性，在太阳能电池、发光二极管、激光器等光电器件中受到广泛关注，但严重影响载流子的弛豫和传输特性的激子?声子之间的相互作用还未得到充分揭示。与广泛研究的三维钙钛矿结构相比，准二维钙钛矿存在天然形成的量子阱结构，具有更大的激子结合能，激子效应更加明显，但对其激子?声子相互作用的研究仍然较少。因此，我们通过溶液法制备了准二维R?P型钙钛矿（PEA）₂Cs_n-1Pb_nBr_3n+1薄膜，其增益系数高达~1 090.62 cm^-1，获得了低阈值（~12.48 μJ/cm²）的放大自发辐射。基于此，我们通过变温荧光光谱（77~300 K）和瞬态吸收光谱技术研究了（PEA）₂Cs_n-1Pb_nBr_3n+1薄膜随温度变化的发光特性，以阐述其内部的激子?声子相互作用对其发光性能的影响。发现在低温域内（77~120 K），由激子?声子相互作用引起的带隙变化相对较弱，晶格热膨胀占主导地位；随着温度升高，激子?声子相互作用对带隙变化产生较大影响。另一方面，激子?声子相互作用会促使发光光谱线宽加宽，但我们在77~120 K的温度范围内观察到了反常线宽变窄现象，这归因于由局域化效应引起的多量子阱中的能量转移机制；直到120 K之后，激子?声子相互作用引起的谱线加宽才足以逆转这一趋势。本文对准二维钙钛矿的激子?声子相互作用的研究对于提高准二维钙钛矿光学性能及其发光应用具有指导价值。

In recent years, all-inorganic halide perovskite quantum dots (QDs) have drawn attention as promising candidates for photodetectors, light-emitting diodes, and lasing applications. However, the sensitivity and instability of perovskite to moisture and heat seriously restrict their practical application to optoelectronic devices. Recently, a facile ligand-engineering strategy to suppress aggregation by replacing traditional long ligands oleylamine (OAm) during the hot injection process has been reported. Here, we further explore its thermal stability and the evolution of photoluminescence quantum yield (PLQY) under ambient environment. The modified CsPbBr3 QDs film can maintain 33% of initial PL intensity, but only 17% is retained in the case of unmodified QDs after 10 h continuous heating. Further, the obtained QDs with higher initial PLQY (91.8%) can maintain PLQY to 39.9% after being continuously exposed in air for 100 days, while the PLQY of original QDs is reduced to 5.5%. Furthermore, after adhering CsPbBr3 QDs on the surface of a micro SiO2 sphere, we successfully achieve the highly-efficient upconversion random laser. In comparison with the unmodified CsPbBr3 QDs, the laser from the modified CsPbBr3 QDs presents a decreased threshold of 79.81μJ/cm2 and higher quality factor (Q) of 1312. This work may not only provide a facile strategy to synthesize CsPbBr3 QDs with excellent photochemical properties but also a bright prospect for high-performance random lasers.

In the past decade, lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode, solar cell, photodetector, and laser, due to their low-cost synthesis method, tunable bandgap, high quantum yield, large absorption, gain coefficient, and low trap-state densities. In this review, we present a comprehensive discussion of lead halide perovskite applications, with an emphasis on recent advances in synthetic strategies, morphology control, and lasing performance. In particular, the synthetic strategies of solution and vapor progress and the morphology control of perovskite nanocrystals are reviewed. Furthermore, we systematically discuss the latest development of perovskite laser with various fundamental performances, which are highly dependent on the dimension and size of nanocrystals. Finally, considering current challenges and perspectives on the development of lead halide perovskite nanocrystals, we provide an outlook on achieving high-quality lead perovskite lasers and expanding their practical applications.

In recent years, halide perovskite nanostructures have had great advances and have opened up a bright future for micro/nanolasers. However, upconversion lasing by two-photon excitation with mode selection and high quality factor in one device is still rarely reported. Herein, two lasing modes are demonstrated in the all-inorganic perovskite CsPb2Br5 microplates with subwavelength thickness and uniform square shape. The net optical gain is quickly established in less than 1 ps and persists more than 30 ps, revealed by ultrafast transient absorption spectroscopy. The temperature-dependent low-threshold amplified spontaneous emission confirms the net gain for stimulated emission with a high characteristic temperature of 403 K, far surpassing the all-inorganic CsPbBr3 semiconductor gain media. Remarkably, upconversion lasing based on two kinds of microcavity effects, Fabry–Pérot and whispering-gallery modes, from the microplates at room temperature is successfully achieved with a low threshold operating in multi- or single-mode, respectively. Surprisingly, the quality factor (～3551) is among the best values obtained from perovskite micro/nanoplate upconversion lasers without an external cavity. Moreover, the highly stable chromaticity with color drift only less than 0.1 nm also outbalances the all-inorganic CsPbBr3 ones. These superior performances of CsPb2Br5 microplate lasing with a facile solution synthesis procedure will offer a feasible structure to fabricate specific functionalities for high-performance frequency upconversion micro/nanoscale photonic integrated devices.