Research On Matrix Of Triplet Annihilation Upconversion Luminescent Material

Upconversion luminescence is a process that uses long wavelength excitation to obtain short wavelength emission.The triplet-triplet annihilation upconversion(TTA-UC)material requires low excitation power density,easy adjustment of excitation and emission wavelengths,and high quantum efficiency of upconversion luminescence.TTA-UC has potential applications in solar cells,photodynamic therapy,bioimaging,and photocatalysis.Therefore,TTA-UC has received extensive attention in recent years and has become a research hotspot.At present,most TTA-UC materials research is still based on solution matrix,and solid matrix has just emerged.Since the triplet energy transfer process of TTA-UC follows the Dexter electron transfer mechanism,it is easier to obtain high up-conversion efficiency in the solution matrix than the solid matrix.However,the solution matrix needs strict oxygen removal and tight sealing,which limits the application of TTA-UC to a certain extent,especially in the field of photovoltaic devices,photocatalysis and newly developed anticounterfeiting coatings.Solid substrates have unique advantages.However,there are still many problems in the existing research of solid matrix,and theoretical research is not sufficient.Therefore,based on the study of up-conversion properties in high-viscosity solvent matrix,this paper aims to study the relationship between the glass transition temperature(Tg)of polymer solid matrix and the up-conversion efficiency.(1)Study the effect of solvent matrix viscosity on the performance of TTA-UC:Solvent viscosity controls the diffusion process,which affects the transfer process of triplet energy.In this paper,the phthalate solvent was chosen for the first time as a representative of medium and high viscosity solvents to study the effect of different viscosity gradients on upconversion performance.Despite the increased viscosity,reducing the rate of the energy transfer process is detrimental to upconversion.However,an increase in viscosity can extend the life of the triplet and promote upconversion.The results show that increasing the acceptor concentration and ensuring the efficiency of the TTET process is 100 %,which can increase the maximum efficiency of TTA-UC in high viscosity solvents.Different from previous research reports: the viscosity of the solvent is increased,and the upconversion efficiency of the upconversion system composed of Bodipy(BDP)and Perylene is lowered.The study further improved the effect of solvent viscosity on the upconversion system.(2)TTA-UC in solid matrix:We use low-cost and easy-to-use polyvinyl chloride(PVC)as the solid matrix.The polymer preparation of the TTA upconversion system is realized by simple preparation method without deoxidation,and the glass transition temperature of PVC is effectively regulated by adding plasticizer.In this study the upconversion efficiency is up to 29.3%.In this paper,the solid-state matrix with different glass transition temperature was prepared by DOP doping PVC.The effect of matrix glass transition temperature on the upconversion efficiency was studied.Combined with free volume theory and diffusion theory,a reasonable explanation was given.As the glass transition temperature of the solid matrix decreases,the free volume of the polymer segment increases,result in diffusion rate increasing.When diffusion rate of small molecules into the polymer increases,both the oxygen permeation rate and energy transfer efficiency increase,and the upconversion efficiency is the result of competition between them.In general,as the glass transition temperature starts to decrease from above room temperature,the upconversion efficiency first increases and then slowly decreases.