Great promise has been shown by all-inorganic 3D lead-free double perovskites (DPs) consisting of the broadband self-trapped exciton (STE). This can act as an alternative to lead halide perovskites in several optoelectronic applications like photodetectors and light-emitting diodes (LEDs).
A basic understanding of the effect of doping on the optical properties of DPs, particularly the STE dynamics is of utmost importance for their performance optimization and applications.
In a study reported in the journal Advanced Science, the research group headed by Professor Xueyuan Chen from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences have engineered a special strategy through Cu+ doping to obtain effective STE emission in the alloyed lead-free Cs2(Ag/Na)InCl6 DP crystals.
This special strategy based on Cu+ doping encourages the STE emission in the alloyed Cs2(Ag/Na)InCl6 DPs. A small amount (1.0 mol%) of Cu+ doping was utilized by the researchers to determine the raised STE emission in the crystals, with photoluminescence (PL) quantum yield rising from 19.0% to 62.6% and excitation band moving from 310 nm to 365 nm.
The researchers extensively surveyed the impact of Cu+ doping on the electronic structure, STE dynamics and optical properties of Cs2(Ag/Na)InCl6. The as-synthesized Cs2(Ag/Na)InCl6: Cu+ crystals show considerably improved PL stemming from the increased radiative recombination rate of STEs and the enhanced STE density.
Through ultrafast femtosecond transient absorption and temperature-dependent PL spectroscopies, the scientists disclosed that the notable PL improvement was attributed to the high density and radiative recombination rate of STEs.
This was as a result of the symmetry breakdown of the STE wavefunction at the octahedral Ag+ site induced by Cu+ doping.
In addition, the scientists illustrated the excellent air, thermal and structural stability of these Cu+-doped Cs2(Ag/Na)InCl6 crystals. Then, they unraveled their huge potential as effective yellow-emitting phosphors for application in near-ultraviolet (NUV)-converted white LEDs.
This study offers a good understanding of the STE dynamics in Cu+-doped Cs2(Ag/Na)InCl6, thereby setting a foundation for the future design of the latest lead-free DPs with effective STE emission.
Cheng, X., et al. (2022) Boosting the Self-Trapped Exciton Emission in Alloyed Cs2(Ag/Na)InCl6 Double Perovskite via Cu+ Doping. Advanced Science. doi.org/10.1002/advs.202103724