Exploration of Nontoxic Cs₃CeBr₆ for Violet Light-Emitting Diodes

Abstract

Violet light-emitting diodes (LEDs) are widely utilized for solid-state lighting, bacteria sterilization, and so on. Herein, the nontoxic and earth-abundant Ce 3+ ion with intrinsic strong violet emission is introduced to substitute Pb 2+ in CsPbBr 3 perovskite for electrically driven PeLEDs. Cs 3 CeBr 6 possesses a zero-dimensional photoactive site with a high photoluminescence quantum yield of ≈90% for both crystals and films. The excited-state lifetime of ≈28 ns enabled by the spin-and parity-allowed Ce-5d → Ce-4f transition is considerably faster than other lanthanide-based luminescent centers. The violet LEDs based on thermally evaporated Cs 3 CeBr 6 films display color-stable spectra with a maximum EQE of 0.46%, representing the first Cs 3 CeBr 6 LED and one of the most efficient violet PeLEDs. Moreover, a white LED with standard color coordinates of (0.339, 0.343) is constructed by combining Cs 3 CeBr 6 -based violet PeLEDs with yellow phosphor downconverters. Our work will motivate further exploration of diverse lanthanide-based perovskites for LEDs and other optoelectronics.

Environment‐Friendly Perovskite Light‐Emitting Diodes: Progress and Perspective

“…As has been proved by the commercial OLEDs industry, this method can accurately control the depositing rates and compositions of the films and the whole PeLED fabrication process is low-cost, solvent-free and convenient for large-scale mass production. [58,59] In 2018, Yuan et al designed experiment to prepare uniform CsSnX 3 film, which sequentially deposited SnBr 2 (50 nm) and CsBr (45 nm) in a vacuum chamber and then annealed at 100 °C for 60 min in a nitrogen-filled glovebox to form final perovskite film. [60] To promote complete reaction of the precursors, vacuum dual-source thermal deposition method was used, which simultaneously deposits two kinds of materials at fixed evaporation ratio.…”

“…[60] To promote complete reaction of the precursors, vacuum dual-source thermal deposition method was used, which simultaneously deposits two kinds of materials at fixed evaporation ratio. [59,[61][62][63][64][65] For example, Figure 1d illustrates the schematic of vacuum dual-source thermal deposition for CsEuBr 3 film, which simultaneously deposited two Note that the whole spin-coating time is defined as 60 s. Reproduced with permission. [49] Copyright 2020, American Chemical Society.…”

“…The final device obtained an EQE of 0.46%, as shown Figure 6h. [59] Although many lead-free PeLEDs with different B-site elements have been fabricated (Table 2), in some extent of which shows potential to realize environment-friendly PeLEDs, there still exist many obstacles to obtain devices suitable for commercial use. In general, the typical device structure of environmentfriendly PeLEDs is Glass/ITO/HTL/Perovskite/ETL/Cathode, while there are also some reports of inverted device structure utilized, which is Glass/ITO/ETL/Perovskite/HTL/Anode.…”

“…[ 60 ] To promote complete reaction of the precursors, vacuum dual‐source thermal deposition method was used, which simultaneously deposits two kinds of materials at fixed evaporation ratio. [ 59,61–65 ] For example, Figure 1d illustrates the schematic of vacuum dual‐source thermal deposition for CsEuBr 3 film, which simultaneously deposited two precursors of CsBr and EuBr 2 . The final film showed a high PLQY of 69%, short excited‐state lifetime of 151 ns, and excellent exciton diffusion diffusivity of 0.022 cm 2 s −1 .…”

Inorganic Lanthanide Compounds with f–d Transition: From Materials to Electroluminescence Devices

“…The Ce 3+ -based perovskite derivative, Cs 3 CeBr 6 , possesses an orthorhombic symmetry space group Pbcm (Figure 4e) with the photoluminescence quantum yield as high as 92.3%. 70 Similar to CsEuBr 3 , the CBM is mainly contributed by the Ce 5d orbital, while the VBM is primarily composed of the Ce 4f orbital. 71 In addition, the fluorescence lifetime of Cs 3 CeBr 6 is about 28.7 ns (Figure 4f and Table 3), which is close to that of perovskite and organic fluorescent light-emitting materials.…”