Research On Photoluminescence Enhancement Of Double Perovskite Cs₂AgInCl₆ Quantum Dots And Its Mechanism

Recent years,the distinctive semiconductor chracteristics and excellent photoelectric performance of lead halide perovskite quantum dots（QDs）have made a significant enhancement in optoelectronic devices.However,the toxicity and instability of lead–based perovskites are ineligible issues,which are major limitations to the commercialization.Inorder to address the toxicity and instability of lead halide perovskite,scientists obtained the metal halide double perovskite by replacing two bivalent cations in B site with a pair of monovalent and trivalent cations,providing more alternative candidates for perovskites.Cs₂AgInCl₆ is a new lead–free double perovskite with a direct band gap,which has attracted great attentions due to their good stability and highly efficient luminescence.However,the parity forbidden transition limites theri photoelectric performance,the quantum yield of Cs₂AgInCl₆ double perovskite at nanocale still hold an unsatisfactory value.So,the synthesis,photoelectric characteristics and photoluminescence enhancement of Cs₂AgInCl₆ double perovskite QDs are explored and researched in this work.Firstly,Cs₂AgInCl₆ QDs are synthesized by injecting trimethyl chlorosilane（TMS–Cl）into the dissolved precursor at 180℃.The as–synthesized Cs₂AgInCl₆ QDs exhibit a weak orange emission peak at 570 nm with a photoluminescence quantum yield（PLQY）of 1.5%,which is derived from the radiative recombination of self trapped excitons（STEs）.Then,in order to break the parity forbidden transition of STE,Cs2Nax Ag1–xInCl6（x=0,0.2,0.4,0.6,0.8,and 1）QDs are obtained by alloying various amounts of Na into Cs₂AgInCl₆ QDs via the same hot injection method,resulting a peak PLQY of 13.4%in Cs₂Na_0.6Ag_0.4InCl₆QDs.At last,a serise of Mn²⁺doped Cs₂Na_xAg_1–xInCl₆ QDs are synthesized by varying the Mn amount and x value systematically,which enhances the PLQY of Cs₂Na_xAg_1–xInCl₆ QDs up to 36%as the highest value.As a result,a red photoluminescence emission peak at 625 nm is observed in Mn²⁺doped Cs₂Na_xAg_1–xInCl₆ QDs,which derives from the ⁴T₁→⁶A₁ transition of Mn²⁺that is related to the ultrafast energy transfer from STE to Mn²⁺.