Tunable Color Temperatures and Efficient White Emission from Cs2 Ag1- x Nax In1- y Biy Cl6 Double Perovskite Nanocrystals

Abstract

Recently, Bi-doped Cs₂ Ag_0.6 Na_0.4 InCl₆ lead-free double perovskites demonstrating efficient warm-white emission have been reported. To enable the solution processing and enrich the application fields of this promising material, here a colloidal synthesis of Cs₂ Ag_{1- x} Na_x In_{1- y} Bi_y Cl₆ nanocrystals is further developed. Different from its bulk states, the emission color temperatures of the nanocrystal can be tuned from 9759.7 to 4429.2 K by Na⁺ and Bi³⁺ incorporation. Furthermore, the newly developed nanocrystals can break the wavefunction symmetry of the self-trapped excitons by partial replacement of Ag⁺ ions with Na⁺ ions and consequently allow radiative recombination. Assisted with Bi³⁺ ions doping and ligand passivation, the photoluminescence quantum yield of the Cs₂ Ag_0.17 Na_0.83 In_0.88 Bi_0.12 Cl₆ nanocrystals is further promoted to 64%, which is the highest value for lead-free perovskite nanocrystals at present. The new colloidal nanocrystals with tunable color temperature and efficient photoluminescence are expected to greatly advance the research progress of lead-free perovskites in single-emitter-based white emitting materials and devices.

Keywords: lead-free perovskites; nanocrystals; tunable color temperature; white emission.