Precise site occupation of Zn2+ in Rb2CuBr3 to regulate exciton recombination for violet luminescence

Abstract

With its tunable bandgap and 385 nm violet emission, Rb2CuBr3 is a promising candidate for violet light-emitting diodes (LEDs). This work provides how Zn2+ doping enhances self-trapped exciton (STE) emission by modulating excited-state dynamics covered key factors in the STE luminescence dynamics. An anti-solvent synthesis strategy is developed to achieve Rb2CuBr3:xZn2+. The lowest defect formation energy (Eform) confirmed that Zn2+ occupation for the Cu⁺ site. X-ray absorption fine structure (XAFS) evidenced that the shortened bond lengths of with stronger Zn-Br has induced the lattice contraction and narrowed the band gap to favor the violet luminescence. Low temperature-dependent photoluminescence spectra (TDPL) with the time-resolved fluorescence spectra (TRF) have illuminated the whole STE dynamics. The increased exciton binding energy (Eb) by 37% effectively has suppressed exciton thermal dissociation to form classical STE process. However, the suppression ration of the non-radiative to radiative recombination rate (knr/kr) is 56.7%. Notably, the non-radiative recombination is depressed extensively. The optimized doping at Rb2CuBr3:0.3Zn2+ results in a maximum photoluminescence quantum yield (PLQY) of 70.6% and an approximate two-fold enhancement in PL intensity. This work provides how Zn2+ doping enhances STE emission by modulating excited-state dynamics. The fabricated violet LED integrates function of efficient curing, exhibiting broad application prospects.