Solution-grown films of CsPbBr nanocrystals imbedded in Cs PbBr are incorporated as the recombination layer in light-emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr and the nanoinclusion composite are measured and analyzed, indicating second-order kinetics in extended and mainly first-order kinetics in the confined CsPbBr , respectively. Analysis of absorption strength of this all-perovskite, all-inorganic imbedded nanocrystal composite relative to pure CsPbBr indicates enhanced oscillator strength consistent with earlier published attribution of the sub-nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr in melt-grown CsBr host crystals and CsPbBr evaporated films.
Water-based liquid scintillators (WbLS) present an attractive target medium for large-scale detectors with the ability to enhance the separation of Cherenkov and scintillation signals from a single target. This work characterizes the scintillation properties of WbLS samples based on LAB/PPO liquid scintillator (LS). X-ray luminescence spectra, decay profiles, and relative light yields are measured for WbLS of varying LS concentration as well as for pure LS with a range of PPO concentrations up to 90 g/L. The scintillation properties of the WbLS are related to the precursor LAB/PPO: starting from 90 g/L PPO in LAB before synthesis, the resulting WbLS have spectroscopic properties that instead match 10 g/L PPO in LAB. This could indicate that the concentration of active PPO in the WbLS samples depends on their processing.
The optoelectronic properties of semiconductor nanoparticles (NPs) depend sensitively on their surface ligands. However, introducing certain organic ligands to the solution-synthesized CZTSe NPs unfavorably suppresses the interaction among those NPs. These organic ligands prevent the NPs from dissolving in water and create an insulating barrier for charge transportation, which is the key property for semiconductor devices. In our study, by adopting Na 2 S to displace the associated organic ligands on Cu 2 ZnSnSe 4 (CZTSe), we obtained high solubility NPs in an environmentally friendly polar solvent as well as excellent charge transport properties. Toxicity of CZTSe: Na 2 S NPs was determined to be around 10 mg/L. Because of the inorganic ligand S 2− around CZTSe NPs, thin films can be easily fabricated by solution processing out of benign solvents like water and ethanol. After annealing, a homogeneous CZTSSe absorbing layer without carbon point defects was obtained. As the S 2− effectively facilitates the electronic coupling in nanocrystal thin films, carrier mobility of the surface-engineered CZTSe enhances from 4.8 to 8.9 cm 2 /(Vs). This raises the possibility for engineering chalcogenide materials by controlling the surface properties during the fabrication process.
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