Synthesis And Optoelectronic Properties Of Lead-free Halide Perovskites Cs₂AgInCl₆

Cs2AgInCl6 emerges as an eminent member of lead free double perovskite family A2(B?B?)X6 which is promising candidate for stable and environmental friendly alternatives to lead halide perovskites.The parity forbidden transition(PFT)of Cs2AgInCl6 with direct bandgap depresses its potential app lications.The structure distortion is one way of broken reverse symmetry.In this work,a series of Cs2AgIn(1-x)BixCl6(x?0.5)samples are prepared.The refiements of XRD patterns for samples display the strong structure distortion with the enlarged octahedron of In(Bi)Cl6 and the contracted AgCk with increasing Bi concentration.The broken PFT due to Jahn-Teller effect results in the maximum emission for Cs2AgIn0.70Bi0.30Cl6.Combining XRD patterns,excitation,emission and absorption spectra with photoluminescence lifetime,emission mechanism is mainly contributed by surface defect and self-trapped exciton(STE).The results demonstrate that control of structural distortions can be robust tool to boost photoluminescence in halide double perovskites.The constant emission in different environmental conditions like high temperature,exposure in UV light and in air as long as one month,and LED performance extend the scope of applications.Low temperature was also applied as a distortion tool.Comparison of PL and XRD data established the fact that high QY is associated with structural distortions of AgCl6 and InCl6 octahedral.Large Huang-Rhys factor and power dependent analysis provide evidence that the emission is mainly contributed by STE.High pressure studies highlighted the role of structural distortions in emission mechanism.For Cs2AgInCl6 and doped samples with 0.15 and 0.25 Bi concentration,PL luminescence enhanced with high pressure.But for 0.5 Bi concentration PL decreased with high pressure.So pressure confirmed the relationship of structural distortions with emissionn.Along with LED application Cs2AglnCl6 was also investigated for as a scintillator.As light yield in x-ray scintillators is directly related to band gap so our bandgap engineering Cs2AgIn(1-x)BixCl6(0?x?50)made it more suitable for high light yields.The wide versatility of Cs2AgIn(1-x)BixCl6(0?x?50)by Bi substitution make it possible for scintillation applications:such as,Cs2AgIn(1-x)BixCl6(0?x?50)emission is dependent on Bi concentration and it is highly sensitive.Cs2AgInCl6 emissive properties additionally improved by engineering of perovskite structure and dimensionality.This new lead free halide perovskite for scintillation properties sensitive for x-ray power.Overall,our studies showed that Cs2AgIn(1-x)BixCl6(0?x ?50)double perovskite single crystals are favorable for X-ray scintillation because of nontoxicity,exceptional sensitivity as well as outstanding stability.