The Dissociation of Exciton During the Lasing of a Single CsPbBr3 Microplate

Room-Temperature Lasing of Sn-Based Perovskite Single-Crystal Microsquare Plates (MSPs)

Lead-free Sn-based metal halide perovskites are low-cost, high-efficiency photoelectric materials with significant potential for micro/nanolasers, addressing the biological and environmental toxicity of lead. This study explores the lasing behavior of single-crystal CsSnBr3 microsquare plates (MSPs) synthesized via two-step high-temperature vapor-phase epitaxy with steady-state and time-resolved photoluminescence (PL and TRPL) spectroscopies. The lasing behavior, dominated by excitons from 193 to 313 K, shows a lasing threshold of 122.5 μJ/cm2 at room temperature, supported by an exciton binding energy of 63.67 meV and a near-unity power-law relationship (k ≈ 1) between PL intensity and pump fluence. The characteristic temperature of the lasing threshold indicates the notable thermal stability of CsSnBr3 MSPs. Moisture is identified as a significant factor causing lasing failure in Sn-based perovskite MSPs. High crystal quality is essential for achieving lasing in micro/nanostructures based on Sn-based perovskites. These findings highlight the potential of high-temperature vapor epitaxial growth for Sn-based perovskite micro/nanolasers, paving the way for environmentally and biologically friendly optoelectronic devices.

Photon Reabsorption and Surface Plasmon Modulating Exciton-to-Dopant Energy Transfer Dynamics in Mn:CsPb(BrCl)3 Quantum Dots

Exciton-to-dopant energy transfer (ET) dynamics of Mn:CsPbX3 quantum dots (QDs), which is dominated by diverse physical factors, requires more comprehensive understanding. Here, the concentration-dependent photon reabsorption effect on ET dynamics has been meticulously analyzed in colloidal Mn:CsPb(BrCl)3 QDs. The results indicate that the photons emitted by the smaller QDs are absorbed by the larger QDs, effectively providing additional excitation light to the latter. The reabsorbed photons play a crucial role in significantly enhancing the ET process in the larger QDs. Additionally, the Mn:CsPb(BrCl)3 QDs/Poly(methyl methacrylate)/Ag/SiO2 multilayer films were fabricated to study the influence of the surface plasmon (SP) on ET dynamics. The results reveal that resonant energy transfer between excitons and SP via dipole interactions can regulate the ET process and Mn2+ emission intensity by controlling the distance between the SP and excitons. These findings provide insights into Mn:CsPbX3 QD ET dynamics and potential methods for controlling their luminescence performance in practical applications.

Unraveling the Luminescence Quenching Mechanism in Strong and Weak Quantum-Confined CsPbBr3 Triggered by Triarylamine-Based Hole Transport Layers

Luminescence quenching by hole transport layers (HTLs) is one of the major issues in developing efficient perovskite light-emitting diodes (PeLEDs), which is particularly prominent in blue-emitting devices. While a variety of material systems have been used as interfacial layers, the origin of such quenching and the type of interactions between perovskites and HTLs are still ambiguous. Here, we present a systematic investigation of the luminescence quenching of CsPbBr3 by a commonly employed hole transport polymer, poly[(9,9-dioctylfluorenyl-2,7diyl)-co-(4,4'-(N-(4-sec-butylphenyl) diphenylamine)] (TFB), in LEDs. Strong and weak quantum-confined CsPbBr3 (nanoplatelets (NPLs)/nanocrystals (NCs)) are rationally selected to study the quenching mechanism by considering the differences in their morphology, energy level alignments, and quantum confinement. The steady-state and time-resolved Stern-Volmer plots unravel the dominance of dynamic and static quenching at lower and higher concentrations of TFB, respectively, with a maximum quenching efficiency of 98%. The quenching rate in NCs is faster than that in NPLs owing to their longer PL lifetimes and weak quantum confinement. The ultrafast transient absorption results support these dynamics and rule out the involvement of Forster or Dexter energy transfer. Finally, the 1D 1H and 2D nuclear overhauser effect spectroscopy nuclear magnetic resonance (NOESY NMR) study confirms the exchange of native ligands at the NCs surface with TFB, leading to dark CsPbBr3-TFB ensemble formation accountable for luminescence quenching. This highlights the critical role of the triarylamine functional group on TFB (also the backbone of many HTLs) in the quenching process. These results shed light on the underlying reasons for the luminescence quenching in PeLEDs and will help to rationally choose the interfacial layers for developing efficient LEDs.