All-inorganic 3D lead-free double perovskites (DPs) with broadband self-trapped exciton (STE) emission have shown great promise as alternatives to lead halide perovskites in various optoelectronic applications such as light-emitting diodes (LEDs) and photodetectors. Fundamental understanding the effect of doping on the optical properties of DPs especially the STE dynamics is of vital importance for their performance optimization and applications.
This unique strategy based on Cu+ doping boosts the STE emission in the alloyed Cs2(Ag/Na)InCl6 DPs. The researchers used a small amount (1.0 mol%) of Cu+ doping to realize the boosted STE emission in the crystals, with photoluminescence (PL) quantum yield increasing from 19.0% to 62.6% and excitation band shifting from 310 nm to 365 nm.
They comprehensively surveyed the effect of Cu+ doping on the electronic structure and optical properties of Cs2(Ag/Na)InCl6 and the STE dynamics. The as-synthesized Cs2(Ag/Na)InCl6: Cu+ crystals exhibit significantly enhanced PL stemming from the increased radiative recombination rate of STEs as well as the improved STE density.
By means of temperature-dependent PL and ultrafast femtosecond transient absorption spectroscopies, the researchers unraveled that the remarkable PL enhancement was ascribed to the increased density and radiative recombination rate of STEs, as a result of symmetry breakdown of the STE wavefunction at the octahedral Ag+ site induced by Cu+ doping.
Besides, the researchers demonstrated the excellent air, structural and thermal stability of these Cu+-doped Cs2(Ag/Na)InCl6 crystals, and revealed their great potentials as efficient yellow-emitting phosphors for application in near-ultraviolet (NUV)-converted white LEDs.
This study provides deep insights into the STE dynamics in Cu+-doped Cs2(Ag/Na)InCl6, thereby laying a foundation for future design of new lead-free DPs with efficient STE emission.
