Liquid Nitrogen Passivation for Deep-Blue Perovskite Quantum Dots with Nearly Unit Quantum Yield

Abstract

Deep-blue metal halide perovskite light-emitting diodes (PeLEDs) (450−470 nm) still fall behind their green and red counterparts in terms of efficiency, luminance, and lifetime, badly suffering from excess intrinsic surface defects of metal halide perovskites. Herein, we presented a liquid nitrogen passivation (LNP) strategy to effectually restrain the defects of surface Br vacancy (V Br ) for high-quality deep-blue MAPbBr 3 quantum dots (QDs). This liquid nitrogen (LN) provides a low-temperature environment to reduce the size of MAPbBr 3 QDs for the green-to-deep-blue emission transformation and impel NH 4 Br to firmly anchor surface Br ions for V Br passivation. These irreversible deep-blue MAPbBr 3 QDs remarkably feature the high photoluminescence quantum yield of 97.64% and the strong stability of 91% remaining photoluminescence intensity against ultraviolet irradiation after 120 min, which are comparable to those of red/green counterparts. Based on these findings, we developed deep-blue PeLEDs with the electroluminescence emission of 455 nm, which is in line with the standard of the National Television Standards Committee (NTSC). Evidently, this LNP strategy may open a way to transform the emission spectra and achieve highquality deep-blue perovskite QDs, promoting the commercial development of deep-blue PeLEDs.

Suppressing Growth Strategy on Synthesizing Stable and High-Quality Blue-Emitting CsPbBr3 Quantum Dots

“…Furthermore, in the high-resolution spectrum of Pb 4f of Figure e, the curve of CsPbBr 3 NCs obtained by CM can fit two species, the signals are assigned to Pb–Br (143.0 and 138.1 eV) and Pb–oleate (142.5 and 137.7 eV) species, respectively . The Pb–oleate signals indicate the existence of the defect of V Br , , which are caused by excessive nucleation and growth rates. On the contrary, the peaks in Figure e of CsPbBr 3 QDs obtained by MM are complete Pb 4f peaks, respectively, meaning that the structure is more complete with fewer defects, which would result in fewer nonradiative recombination defects due to the slower nucleation rate.…”

Tunable Green-to-Blue Light Emitting Hybrid Perovskite Nanocrystals: Status Updates and Roadblocks

“…114 To further passivate the defects generated through halide ions and improve the properties of blue-emissive NCs, a liquid nitrogen passivation strategy was also designed. 109 This method effectively stabilized the blue-emitting MAPbBr 3 perovskite NCs, resulting in emission in the range of 470−490 nm (Figure 13b). This strategy majorly works on the correlation between size and temperature.…”

“…(b) Schematic illustration of blue-emitting perovskite QDs obtained through liquid nitrogen passivation. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…Later, ligand-assisted solid phase synthesis (LASPS) using MACl as the solid powder was proposed to improve the stability of MAPbBr 3 NCs through passivation of defects generated by bromide ions and leading to PLQY of 85% . To further passivate the defects generated through halide ions and improve the properties of blue-emissive NCs, a liquid nitrogen passivation strategy was also designed . This method effectively stabilized the blue-emitting MAPbBr 3 perovskite NCs, resulting in emission in the range of 470–490 nm (Figure b).…”

Structurally Tolerance-Factor-Tuned Metal Halide Nanocrystals for Environmentally Stable and Efficient Red Light-Emitting Diodes

“…Metal halide perovskites (MHPs), a newly emerged excellent and potential semiconductor material, yield unusually brilliant results in the field of perovskite light-emitting diodes (PeLEDs) . In particular, their unique high photoluminescence (PL) efficiency, narrow emission line width, and tunable emitting wavelength make them one of the most promising candidates for next-generation displays and illumination devices. − With sustained efforts in recent years, the stability of blue- and green-emitting perovskite NCs has shown significant improvement. − However, the black phase of MHPs (CsPbI 3 ) with the edge tolerance factor ( t ) of 0.81 will spontaneously and easily transform into a nonperovskite orthorhombic (δ) yellow phase at room temperature. − Such an undesired phase degradation process has greatly impeded the promotion of red light-emitting diode efficiency. , This exceedingly unbalanced development of the three primary colors triggered by the poor stability of red perovskite seriously hinders the further practical commercial application of PeLEDs. ,, Therefore, achieving high stability is still a huge challenge for commercial applications of red PeLEDs.…”