Syntheses And Luminescence Mechanism Of Novel Green-to-red Conversion Phosphors

Solar spectral conversion has been considered as a way to improve the efficiency of solar energy conversion in the photosynthetic process of agricultural crops to augment their production since the early 1970s.Serving as one of the important solar spectra conversion materials,the synthesis and research of green-to-red(GTR)conversion phosphors are of great significance in human development and social economy.So far,agricultural GTR conversion phosphors whose spectral properties completely meet the needs of plants growth are quite limited,primarily Eu2+-doped chalcogenide phosphors.Hence,experts in luminescence field are always devoting themselves to seeking for new types of GTR conversion phosphors.Meanwhile,for the sake of environmental sustainable development,an important and pressing task is to develop some green synthetic technique for the known Eu2+-doped GTR conversion chalcogenide phosphors in agricultural application of solar energy field.1.Synthesis and luminescent mechanism of novel GTR conversion phosphors Ba2ZnS3:Eu2+,X-(X=Cl,Br,I)Ba2ZnS3:Eu2+ has been reported as a red phosphor with a broad emission band peaking at 650 nm under blue excitation for white-LED.In this study,halide ions are doped into Eu2+-activated Ba2ZnS3 phosphors for the first time.It is demonstrated that halogenation effect makes a great contribution to increase the green-excitation intensity of Ba2ZnS3:Eu2+,X-(X=Cl,Br,I)phosphors.As the excitation spectra exhibit,green-excitation intensity successively strengthens from Cl-,to Br-,to I-due to an increasing halogenation effect.Defect chemistry theory and crystal field theory provide insights into the key role of halide ions in enhancing green-excitation intensity.As far as we know,this is the first time to achieve GTR conversion in Eu2+-doped Ba2ZnS3 phosphor.After further modifications,this novel GTR conversion phosphor Ba2ZnS3:Eu2+,I-can be utilized for solar spectral conversion in agricultural field.2.Synthesis and light-conversion adjustment of Ba2ZnS2.82I0.18:Eu2+,Mn2+phosphorsA series of Ba2ZnS2.82I10.18:Eu2+,Mn2+ phosphors are synthesized via a carbon thermal reduction process.It's verified that improved GTR conversion efficiency is gained due to a combination of green excitation from Eu2+ and Mn2+.In addition,the light conversion efficiency of host from ultraviolet to red(UVTR)is also raised.The light-conversion efficiency of GTR or UVTR can be adjusted by altering Eu2+/Mn2+ratios.The optimized Ba1.995Zn0.985S2.82I0.18:0.5%Eu2+,1.5%Mn2+ phosphor can serve as a novel solar spectral conversion agent for agricultural application owing to the well-matched photoluminescent spectra.3.Preparation of alkaline earth sulfide phosphors by an intermediate phase transition metathesis strategy and the corresponding solar conversion compositeA novel intermediate phase transition metathesis strategy is developed to prepare(Ca,Sr)S:Eu2+ solid solution phosphors based on green chemistry.ZnS serves as vulcanizing agent without adopting any other toxic sulfur-bearing gases.The formation of CaS attributes to thermal decomposition of the intermediate state of CaZnOS which is from a combination of ZnS and CaO.The influence of Sr/Ca ratios on the compositions and luminescence properties of(Ca,Sr)S:Eu2+phosphors is also investigated.Besides,in order to overcome the disadvantage that sulfide phosphors are easy to decompose when exposed to moisture,a solar energy conversion laminated glass is fabricated from sunlight conversion resin equipped with optical properties of CaS:Eu2+phosphor,which is proved to be a promising and permanent functional solar spectrum conversion device for greenhouse and green agriculture.