Efficient Thermally Activated Delayed Fluorescence from All‐Inorganic Cesium Zirconium Halide Perovskite Nanocrystals

Abstract

Thermally activated delayed fluorescence (TADF) is generally observed in solid-state organic molecules or metalorganic complexes. However, TADF in all-inorganic colloidal nanocrystals (NCs) is rare. Herein, we report the first colloidal synthesis of an air-stable all-inorganic lead-free Cs 2 ZrCl 6 perovskite NCs. The Cs 2 ZrCl 6 NCs exhibit long-lived triplet excited state (138.2 ms), and feature high photoluminescence (PL) quantum efficiency (QY = 60.37 %) due to TADF mechanism. The emission color can be easily tuned from blue to green by synthesizing the mixed-halide Cs 2 ZrBr x Cl 6Àx (0 x 1.5) NCs. Femtosecond transient absorption and temperature dependent PL measurements are performed to clarify the emission mechanism. In addition, Bi 3+ ions are successfully doped into Cs 2 ZrCl 6 NCs, which further extends the PL properties. This work not only develops a new lead-free halide perovskite NCs for potential optoelectronic applications, but also offers unique strategies for developing new inorganic phosphors.

Experimental and Theoretical Investigation of the Structural and Opto‐electronic Properties of Fe‐Doped Lead‐Free Cs2AgBiCl6 Double Perovskite

“…Another promising approach is hetero‐valent metal substitution. In this approach, two divalent Pb 2+ ions are replaced with a pair of one trivalent B 3+ and monovalent B + cation, leading to the formation of A 2 B I B III X 6 double perovskite materials, which persist the 3D crystal structure and the charge neutrality of perovskite [19–23] . Furthermore, incorporating another new element into the double perovskite structure guides the optical and structural properties depending on chemical compositions [24] .…”

Lead‐Free Halide Double Perovskite Nanocrystals for Light‐Emitting Applications: Strategies for Boosting Efficiency and Stability

“…Subsequently, the aliovalent Bi 3+ doped Cs 2 ZrCl 6 nanocrystals were reported. [ 163 ] The Bi 3+ doped Cs 2 ZrCl 6 nanocrystals showed two additional PL excitation peak at 362 and 310 nm, while the PL excitation peak of Cs 2 ZrCl 6 nanocrystals was located at 245 nm. Hence, the Bi 3+ doped nanocrystals exhibited bright bluish emission at 449 nm under 365 UV light, while undoped Cs 2 ZrCl 6 nanocrystals only exhibited negligible PL emission, which indicated that Bi 3+ doping could adjust PL excitation peak.…”

Alkylamine screening and zinc doping of highly luminescent 2D tin-halide perovskites for LED lighting

“…7,8 Thus, lead-free halide perovskites (LFHPs) with similar optoelectronic properties with LHPs have been broadly studied. [9][10][11][12][13][14] Tin-halide perovskites have drawn most attention for substitution of lead in all optoelectronic applications field. [15][16][17] However, owing to the lack of an inert pair effect as in Pb 2+ , divalent state of Sn is easily oxidized from +2 to +4 state, causing deep defects in perovskites.…”