Bi3+/Sb3+ co-doped Cs2HfCl6 vacancy-ordered double perovskites for multifunctional optoelectronic applications

Abstract

Non-toxic lead-free vacancy-ordered double perovskites (DPs) are attracting more and more wide interest, thanks to their environment- and eco-friendly nature with exciting applications in modern optoelectronic devices. However, most intrinsic vacancy-ordered DPs exhibit a simple luminescence mode with poor photoluminescence (PL) quantum yield (QY). Herein, we report the exploration of ns²-type ion (Bi³⁺ and Sb³⁺) co-doped vacancy-ordered DP Cs₂HfCl₆ microcrystals (MCs) by a room-temperature precipitation method. Different to single-dopant analogues, the co-doped DPs deliver dual emission bands, which are sensitive to the excitation wavelength and tunable across the full-color region. It is verified that the emission band peaked at 460 nm should have originated from the triplet self-trapped excitons (STEs) of Bi³⁺ with a lifetime of hundreds of nanoseconds, while that peaked at 590 nm should be ascribed to the microsecond-timescale STEs of Sb³⁺, respectively. Accordingly, based on these co-doped DPs, high-performance devices such as multi-color anti-counterfeiting and single-component white light emitting diodes (WLEDs) (CIE = (0.344, 0.337), CRI = 84) have been achieved. Moreover, the as-assembled optical temperature sensor exhibits relative sensitivity (S_R) and absolute sensitivity (S_A) of 1.2% K⁻¹ and 0.013 K⁻¹, respectively, representing their bright future toward multifunctional optoelectronic applications.