Co-doping of tellurium with bismuth enhances stability and photoluminescence quantum yield of Cs2AgInCl6 double perovskite nanocrystals

Abstract

The co-doping of double perovskites is a useful approach in terms of improving their stability and photoluminescence quantum yield. Herein, Bi³⁺ and Te⁴⁺ cations have been co-doped into Cs<inf>2</inf>AgInCl<inf>6</inf> nanocrystals. Doping with Te⁴⁺ cations promotes radiative recombination of self-trapped excitons due to increased defect formation energies of silver and indium vacancies, according to experimental and theoretical results. When used in excess, the TeO<inf>2</inf> precursor would generate residual TeO<inf>2</inf>, Te<inf>2</inf>O<inf>3</inf>Cl<inf>2</inf>, R<inf>2</inf>TeO, or all three of them, which confined undesired chlorine ions on oxygen vacancies to counteract the pull from the Cs<inf>2</inf>AgInCl<inf>6</inf> host, resulting in improved coordination with surface oleic acid ligands. As a result, 1% Bi and 8% Te co-doped Cs<inf>2</inf>AgInCl<inf>6</inf> nanocrystals reach a high photoluminescence quantum yield of 34% and show an improved stability, maintaining over 70% of their original emission intensity after storage for more than 1 month. These findings are important in the context of producing high-performance properly doped double perovskite nanocrystals for optoelectronic applications.