Fabrication and temperature-dependent photoluminescence spectra of Zn–Cu–In–S quaternary nanocrystals

A series of Zn-Cu-In-S nanocrystals （ZCIS NCs） are prepared and the optical properties of the ZCIS NCs are tuned by adjusting the reaction time. It is interesting to observe that the temperature-dependent photoluminescence （PL） spectra of the ZCIS NCs show a redshift with decreasing intensity at low temperature （50-280 K） and a blueshift at high temperature （318--403 K）. The blueshift can be explained by the thermally active phonon-assisted tunneling from the excited states of the low-energy emission band to the excited states of the high-energy emission band.

Temperature-dependent photoluminescence of size-tunable ZnAgInSe quaternary quantum dots

Colloidal ZnAgInSe（ZAISe） quantum dots（QDs） with different particle sizes were obtained by accommodating the reaction time. In the previous research, photoluminescence（PL） of ZAISe QDs only could be tuned by changing the composition. In this work the size-tunable photoluminescence was observed successfully. The red shift in the photoluminescence spectra was caused by the quantum confinement effect. The time-resolved photoluminescence indicated that the luminescence mechanisms of the ZAISe QDs were contributed by three recombination processes. Furthermore, the temperature-dependent PL spectra were investigated. We verified the regular change of temperature-dependent PL intensity, peak energy, and the emission linewidth of broadening for ZAISe QDs. According to these fitting data, the activation energy（？E） of ZAISe QDs with different nanocrystal sizes was obtained and the stability of luminescence was discussed.

Carrier Recombination of Organic-Inorganic 3D Halide Perovskite Single Crystals

Organic-inorganic 3D halide perovskite materials recently have become one of the major players of hybrid semiconductors for photovoltaic and optoelectronic applications.The diffusion length of charge carriers is one of the critical parameters for justifying photovoltaic applications of materials.In this work,we propose a realistic kinetic model in order to fully understand carrier relaxation rate of photoexcited organic perovskites with a negligible exciton formation in photoluminescence lifetime measurements.We find that the extraction of carrier relaxation rate has to be made from multiple fluence-dependent photoluminescence lifetime measurements with global fittings,instead of a traditional single fluence lifetime measurement.To demonstrate the validity of the model,two kinds of p-doped CH3NH3PbI3 single crystals were grown up by intentionally increasing defects.Global fittings of the kinetic model to the two kinds of single crystals yield doping density,trap density,and recombination constants.Our methodology provides a self-contained approach to determine diffusion lengths of organic 3D halide perovskite materials.

Vacuum Packaging Sensor Based on Time-Resolved Phosphorescence Spectroscopy

Intelligent food packaging with the multisensory analysis is promising as the next generation technology of food packaging.The oxygen content in food packaging is one of the crucial parameters affecting the food quality and shelf life.Caviar is among the most nutritious and costly food sources.Here,a photonic oxygen-sensing system,based on the time-resolved phosphorescence spectroscopy of a platinum complex,is developed for non-contact,non-intrusive,and real-time vacuum packaging quality control,and implemented for caviar packaging.The sensor is embedded in protective polyethylene layers and excited with a short-pulsed light emitting diode(LED)source.Integration of a blue pulsed light source,a fast and amplified silicon photodiode controlled by the Spartan-6 field programmable gate array(FPGA),and a long lifetime platinum complex results in a photonics-based oxygen sensor with a fast response and high sensitivity to the vacum packaging damage,which is suitable for caviar.It is revealed that applying the polyethylene layers protects the caviar from the platinum complex,leaching while not interfering with the sensor functionality.Characterizing the photonic system based on its sensitivity,repeatability,stability,and long-term operation demonstrates its capability for this application.