For next-generation high-definition displays, the newly recommendation 2020 (Rec. 2020) standard calls for the emission wavelength of green emitters to be kept at 525–535 nm with narrow emission line width below 25 nm. All-inorganic lead halide perovskite CsPbBr3 nanocrystals (NCs) with sharp emission seem as the prefect one to match the call, however, it is a great challenge to tune their emission wavelength to the target window of 525–535 nm because of the intrinsic band gap of CsPbBr3. Herein, we report a facile strategy to prepare CsPbBr3 NCs with finely tunable emissions in the narrow range of 525–535 nm by establishing a CsPbBr3–Cs4PbBr6:Na Type II structure. The doping of the Na ions is the key factor to construct the Type II structure, which induces the formation of the Cs4PbBr6:Na phase and builds CsPbBr3–Cs4PbBr6:Na Type II structure, leading to the tunable emission wavelength of CsPbBr3 NCs. The as-synthesized CsPbBr3 NCs exhibit an ideal emission at 525–535 nm with a narrow emission line width of 23 nm and a high photoluminescence quantum yield (PLQY) of 85%. As a green downconverter, an ultrapure green backlight covers 97% of the Rec. 2020 standard in the CIE 1931 color space, representing the “greenest” backlight up to now.
Colloidally quantum-confined CsPbBr 3 nanoplatelets (NPLs) exhibit narrow emission linewidths and thickness-tunable photoluminescence, making them ideal candidates for deep-blue perovskite light-emitting diodes (PeLEDs). However, the weak surface coordination of conventional long-chain ligands ( e.g ., oleylamine and oleic acid) leads to face-to-face stacking of the NPLs, resulting in undesirable emission redshifts in their PeLEDs. Herein, we report an efficient deep-blue PeLED based on colloidal CsPbBr 3 NPLs that meet the Rec.2020 color standard, enabled by an acid-assisted ligand passivation strategy. Surface chemical analysis reveals that hydrobromic acid facilitates proton-assisted stripping of the long-chain ligands, followed by the formation of stable Pb-S-P coordination bonds with thio-tributylphosphine, which exhibits a high adsorption energy (E ads = -1.13 eV). This approach significantly improves surface defect passivation, yielding a photoluminescence quantum yield of 96% and a narrow 13 nm full-width-at-half-maximum deep-blue emission. Enhanced exciton recombination and reduced defect state density are evidenced by a prolonged photoluminescence lifetime and slower absorption bleach recovery kinetics. The resulting PeLEDs achieve record-breaking performance among CsPbBr 3 NPL-based systems, with a maximum external quantum efficiency of 6.81% at 461 nm, a peak luminance of 143 cd m -2 , and the CIE color coordinates (CIE-y = 0.046) that comply with Rec.2020 standards. This work presents an effective strategy for developing efficient and stable deep-blue perovskite emitters, demonstrating significant potential for the commercialization of perovskite nanomaterials in next-generation ultra-high-definition displays.
Although tremendous efforts have been made to enhance the stability of lead halide perovskite quantum dots (PeQDs), they cannot meet the long-term requirements of photoelectric devices due to their poor reliability when attacked by multiple factors. Herein, we report ultrastable CsPbBr 3 :Sr/PbBr(OH)/molecular sieve composites with a high photoluminescence quantum yield of 75% and high overall stability when exposed to water, blue light and heat, owing to (i) the increased formation energy of CsPbBr 3 PeQDs by Sr doping and (ii) good encapsulation by PbBr(OH) and molecular sieves. These composites maintain 54% of their initial intensity after being aged at 85 °C and 150 mW cm −2 for 720 min, which is superior to commercial green CdSe-based QDs. These promising composites are then used to produce Mini-LED backlights with a high luminous efficacy of 86 lm/W and a color area of ~124% of the National Television Standards Committee or 93% of the Rec. 2020 standards by combining them with red CdSe/CdS/ZnS QDs and a blue Mini-LED chip. We believe that highly reliable PeQDs can be achieved by building well-designed composite structures, thus enabling them to be practically applied in emerging lighting and displays.
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