Synthesis of a Bi3+-Doped Cs2HfCl6 Double Perovskite with Highly Efficient Blue Light Emission at Room Temperature.

Lead-free perovskites have been widely studied due to their environmental friendliness and high stability. In this study, Bi3+-doped Cs2HfCl6 has been synthesized at room temperature. Different from the emission of the Cs2HfCl6 host (452 nm), Bi3+:Cs2HfCl6 can produce a bright blue emission at an excitation wavelength of 350 nm, which is derived from the 3P1 → 1S0 transition of Bi ions and accompanied by the properties of self-trapped excitons. Moreover, 7%Bi3+:Cs2HfCl6 shows excellent stability with the photoluminescence quantum yield reaching up to 69.08%. Meanwhile, a light-emitting diode that is close to pure white light has been fabricated by using 7%Bi3+:Cs2HfCl6, which has a high color rendering index of 92.5. These results show that Bi3+:Cs2HfCl6 would be a potential candidate in the field of inorganic luminescent materials.