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Abstract This study presents an eco-friendly mechanochemical synthesis of cesium lead bromide (CsPbBr₃), eliminating the need of organic solvents and high temperatures. The synthesized CsPbBr₃powder is used to fabricate poly(methyl methacrylate) (PMMA)-CsPbBr₃films and CsPbBr₃nanocrystals (NCs). The photoluminescence (PL) peaks of the emission light are centered at 541 nm, 538 nm, and 514 nm for the CsPbBr₃powder, PMMA-CsPbBr₃films, and CsPbBr₃NCs, respectively, correlating with crystal sizes of 0.96, 0.56, and 0.12μm, respectively. The PL lifetime analysis reveals decay times ( ${\tau }_1,{\tau }_2$) of (4.18, 20.08), (5.7, 46.99), and (5.81, 23.14) in the units (ns, ns) for the CsPbBr₃powder, PMMA-CsPbBr₃films, and CsPbBr₃NCs, respectively. The PL quantum yield of the CsPbBr₃NCs in toluene is 61.3%. Thermal activation energies for thermal quenching are 217.48 meV (films) and 178.15 meV (powder), indicating improved thermal stability with the PMMA encapsulation. The analysis of the PL intensity decay from water diffusion in the PMMA-CsPbBr₃films yields 1.70 × 10⁻¹²m²s⁻¹for the diffusion coefficient of water, comparable to that for water diffusion in pure PMMA. This work demonstrates a scalable, sustainable strategy for CsPbBr₃synthesis and stability enhancement for optoelectronic applications. 

Lead toxicity has hindered the wide applications of lead halide perovskites in optoelectronics and bioimaging. A significant amount of effort has been made to synthesize lead-free halide perovskites as alternatives to lead halide perovskites. In this work, we demonstrate the feasibility of synthesizing CsSnI3-based powders mechanochemically with dual light emissions under ambient conditions from CsI and SnI2 powders. The formed CsSnI3-based powders are divided into CsSnI3-dominated powders and CsSnI3-contained powders. Under the excitation of ultraviolet light of 365 nm in wavelength, the CsSnI3-dominated powders emit green light with a wavelength centered at 540 nm, and the CsSnI3-contained powders emit orange light with a wavelength centered at 608 nm. Both the CsSnI3-dominated and CsSnI3-contained powders exhibit infrared emission with the peak emission wavelengths centered at 916 nm and 925 nm, respectively, under a laser of 785 nm in wavelength. From the absorbance spectra, we obtain bandgaps of 2.32 eV and 2.08 eV for the CsSnI3-dominated and CsSnI3-contained powders, respectively. The CsSnI3-contained powders exhibit the characteristics of thermal quenching and photoelectrical response under white light. 

Abstract The phase stability of mixed halide perovskites plays a vital role in the performance and reliability of perovskite-based devices and systems. In this work, we incorporate the contribution of the strain energy due to the size mismatch of halideions in Gibbs free energy for the analysis of the phase stability of mixed halide perovskites. Analytical expressions of the chemical potentials of halide ions in mixed halide perovskites are derived and used to determine the critical atomic fractions of halide ions for the presence of spinodal decomposition (phase instability). The numerical analysis of CH₃NH₃PbI_xBr_3-xmixed halide perovskite reveals the important role of the mismatch strain from halide ions in controlling the phase instability of mixed halide perovskite, i.e., increasing the mismatch strain widens the range ofxfor the phase separation of mixed halide perovskites. To mitigate the phase instability associated with the strain energy from intrinsic size mismatch and/or light-induced expansion, strain and/or field engineering, such as high pressure, can be likely applied to introduce strain and/or field gradient to counterbalance the strain gradient by the mismatch strain and/or light-induced expansion.