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Present work demonstrate an efficient strategy of regulating the molecular conformation in PEDOT:PSS for ordered PEDOT domains and favorable band alignment, leading to the formation of true-blue PeLEDs with peak EQE up to 6.86% and maximum luminance of 854.10cd/m2 at wavelength of 478 nm. And we achieved the success of air-processed blue PeLEDs based on PFOA modified PEDOT:PSS. [Display omitted] • PFOA regulates the molecular conformation of PEDOT:PSS, improving carrier transport and alignment with the perovskite layer. • The PeLEDs with PFOA reach a peak external quantum efficiency of 6.86 % and a maximum luminance of 854.10 cd/m2 at a wavelength of 478 nm, which are the record values for the pure-bromide quasi-2D PeLEDs in the true-blue region. • The blue PeLEDs were successfully fabricated under ambient conditions (≈25 % RH and 20 °C), owing to the hydrophobic fluorine-carbon (C-F) chains of PFOA. The pure-bromide quasi-2D perovskite has shown advantages in fabrication of blue perovskite light-emitting diodes (PeLEDs) due to its relatively good color stability and capability of moisture resistance. However, the performances of efficiency and luminance of pure-bromide quasi-2D PeLEDs with true-blue (470 nm−480 nm) emission are still inferior. Here, we show a interfacial modification strategy of involving perfluorooctanoic acid (PFOA) to a hole transport layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), to improve the performances of the true-blue PeLEDs. The PFOA regulates the molecular conformation of PEDOT:PSS, forming ordered PEDOT domains that improves the carrier transport and a more favorable band alignment with the perovskite emissive layers. The achieved true-blue PeLEDs show peak EQE of 6.86 % and maximum luminance of 854.10 cd/m2 at wavelength of 478 nm, which are the record values for the pure-bromide quasi-2D PeLEDs in true-blue region. Moreover, owing to the hydrophobic fluorine-carbon (C-F) chains of PFOA, we successfully fabricate the blue PeLEDs in air condition without inert gas protection. This work paves the way for commercial applications in next-generation display technologies. [ABSTRACT FROM AUTHOR]

Taurine (3S) inhibits heat-induced Ostwald ripening by binding to perovskite. 3, 3-diphenylpropylamine (DPPA) improves hydrophobicity to suppresses moisture-induced phase disproportionation. As a result, perovskite films with 3S and DPPA maintain stability for over 200h at 70 °C and over 310 h at 20% relative humidity, achieving the most stable blue quasi-2D perovskite emitters. [Display omitted] • Studying the optical property evolution of blue perovskite under stimuli of moisture and heat. • Proposing a strategy to curb Ostwald ripening and phase disproportionation in blue perovskite. • Achieving one of the most stable blue perovskite films under stimuli of moisture and heat. Quasi-2D metal halide perovskite is rising for efficient blue light-emitting diodes due to strong quantum confinement and tunable emission, while a challenge remains in its poor stability of n -phase distribution under external stresses. Herein, the stable blue quasi-2D perovskite under heat and moisture conditions is achieved by dual ligand engineering. The Lewis base moieties − SO 3 − from taurine (3S) bind tightly with perovskite edges, inhibiting Ostwald ripening of the perovskite phase caused by the heat, and 3, 3-diphenylpropylamine (DPPA) provides a strong hydrophobicity to the perovskite film, suppressing phase disproportionation induced by the moisture. Accordingly, the blue perovskite film, modified synergistically by the 3S and DPPA dual ligands, maintains its initial photoluminescence quantum yield (PLQY) after over 200 h with 70 °C heating, and only exhibiting a redshift in PL peak wavelength less than 10 nm. Exposing under environment condition of 20 % relative humidity for 300 h, the blue perovskite film still retains its initial PL peak wavelength with PLQY exceeding 50 % of the initial value. This achievement establishes a notable strategy for enhancing both the thermal and moisture stability of blue quasi-2D perovskite. Furthermore, the light-emitting diodes based on the perovskite films display the enhanced operating stability. This work offers an efficient strategy for stabilizing blue quasi-2D perovskite and the corresponding devices for the display application. [ABSTRACT FROM AUTHOR]

A stable velocity field distribution of antisolvent flow enables the synthesis of efficient FAPbI 3 perovskite NCs with achieved ∼100 % PLQY and low defect density (∼0.2 cm−3 per NCs) without applying functional additives or further encapsulation. The NCs show incredible reproducibility and remarkable stability of maintaining over 80 % PLQY in an ultra-diluted concentration of 9.3×10-6 mg/mL. [Display omitted] Achieving highly stable and efficient perovskite nanocrystals (NCs) without applying functional additives or encapsulation, particularly sustaining the stability in ultra-dilute solution, is still a formidable challenge. Here, we show the FAPbI 3 perovskite NCs with achieved ∼100 % photoluminescence quantum yield (PLQY) and low defect density (∼0.2 cm−3 per NCs), which is obtained by controlling the velocity field distribution of antisolvent flow in ligand-assisted reprecipitation process. The NCs show incredible reproducibility with narrow deviation of PLQY and linewidth between batch by batch, as well as remarkable stability of maintaining over 80 % PLQY, either in an ultra-diluted solution (9.3 × 10-6 mg/mL), or storing in ambient condition after 90 days with concentration of 0.09 mg/mL. The results in this work demonstrate the interplay of fluid mechanics and crystallization kinetics of perovskite, which pioneers a novel and unprecedent understanding for improving the stability of perovskite NCs for efficient quantum light source. [ABSTRACT FROM AUTHOR]

Metal-halide perovskite nanocrystals (NCs) are promising semiconductor materials for the application of novel nano-optoelectronic devices and light sources, which have attracted wide attention in recent years. Many additives were applied for modulating the electronic structure, as well as improving the stability or light efficiency of the perovskite NCs, particularly the zwitterionic molecules show strong and unique interaction with perovskite lattice to passivate the defects and surface state of the perovskite NCs. Here, in this work, we synthesized the blue CsPbBr 3 perovskite NCs with the assist of zwitterionic straight-chain amino acids, and systematically studied the interaction between the perovskite and amino acids with varied molecular structure. We found that the polarization of the amino acid molecules dominates the ionized state of the two functional groups of -NH 2 and -COOH, leading to different interaction with perovskite. Eventually, the perovskite NCs with 7-aminophenic acid show stable and efficient blue light emission at peak wavelength of 475 nm with achieved light efficiency of ∼ 90%. This work demonstrated the mechanism of the interaction between series zwitterionic amino acids and perovskite experimentally, which provides a guideline for the additive selection and design. [Display omitted] [ABSTRACT FROM AUTHOR]