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The fabrication of blue perovskite light‐emitting diodes (PeLEDs) in air conditions promises to liberate the manipulation procedures from the protection of inert atmosphere in the glovebox, which will remarkably promote the commercialization proceeding of perovskite‐based optoelectronic devices in display applications. However, achieving air‐processed blue PeLEDs in the interference of moisture meets great challenges in crystallization kinetics control. Herein, it is proposed that substrate‐adsorbed moisture dominates the perovskite crystallization kinetics during the fabrication in air, and the limited moisture from nonhygroscopic substrate inhibits the nucleation of the large‐n phase and allows the growth of the small‐n phase, thus yielding blue quasi‐2D perovskite films in a wide moisture range of 10–50% relative humidity. Then, air‐processed blue PeLEDs are successfully achieved for the first time, showing a brightness of 968 cd m−2, external quantum efficiency of 2.54% at stable peak emission of 483 nm, as well as an outstanding operating stability of 546 s at a peak brightness of 45 cd m−2, which are favorably competitive with PeLEDs fabricated in the glovebox. This work provides a guideline for air‐processed blue PeLEDs fabrication, which paves the way for air‐processed PeLEDs in further application of commercialization display. [ABSTRACT FROM AUTHOR]

Interfacial loss arising from defect trapping, contact barrier, and energy level alignment in the emerged perovskite solar cells (PSCs), is one of the most important issues to address for both improved photoconversion efficiency and long‐term operational stability. The recent endeavors on the interfacial embedding of nanocrystals (NCs) in desired locations of PSCs have shown great success in terms of eliminating the interfacial loss in PSCs, while there is a lack of review to summarize the advances of NCs embedding for improved carrier dynamics and inhibited environmental degradation. Present study systematically analyzes the recent achievements on the embedding of a series of NCs including carbon dots, perovskite NCs, II‐VI semiconductor NCs, metal/alloy NCs, which are intentionally introduced in desired layers/interfaces of PSCs. The specific functionality of the NCs embedding including carrier dynamic modulation, crystallinity enhancement, defect passivation, light trapping, and stability enhancement are sorted out, according to the requirement of each layer in PSCs. Finally, the current challenges and future perspectives of NCs embedding for perovskite‐based optoelectronic devices is outlook. The present study provides a guide for developing NCs‐based additives for high‐performance PSCs is believed. [ABSTRACT FROM AUTHOR]

Metal halide perovskite microwires (MWs) have emerged as promising photoactive materials for highly efficient photodetectors (PDs). However, large‐scale MWs film fabrication is still a formidable challenge for achieving integration compatible perovskite PDs arrays, owing to precipitation and structure crushing of MWs during deposition and annealing. Herein, a strategy of fabrication of inch‐scale perovskite MWs films is presented by depositing perovskite intermediate suspension through spray‐coating, which addresses the trade‐off present between the high flatness of MWs film and its large‐scale fabrication. The single crystalline perovskite MWs weave a film with high enough flatness rendering narrow performance distribution of high efficiency on the 7 × 7 PDs arrays. The formamidinium lead iodide (FAPbI3) PDs arrays show average responsivity and detectivity of (1.60 ± 0.46) A W−1 and (1.49 ± 0.50) × 1012 Jones. The methanaminium lead iodide (MAPbI3) PDs arrays show average responsivity and detectivity of (0.065 ± 0.046) A W−1 and (2.54 ± 0.77) × 1011 Jones. The champion PDs based on FAPbI3 MWs film and MAPbI3 MWs film show detectivity of 1.26 × 1013 and 9.67 × 1011 Jones, which are much higher than that of corresponding polycrystalline films and located on the top ranking of similar devices. [ABSTRACT FROM AUTHOR]

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]

Quasi‐2D perovskite exhibits excellent luminescence properties for highly efficient perovskite light‐emitting diodes (PeLEDs). However, the lattice degradation and crystalline phase transition induced by water limit the PeLED's development for application and commercialization. It is demonstrated that the organic additives effectively reduce the defect density, while the bonding strength of these organics and perovskite becomes weak under the high electric field and the Joule heat in an operating PeLED. Thus, an alternative additive for forming strong bonding with perovskite is promising to improve the stability of perovskite film and PeLEDs simultaneously. Here, it is shown that octylammonium sulfate decoration effectively enhances the moisture durability of PEA2(CsPbBr3)4PbBr4 quasi‐2D perovskite film by generating PbSO4 on the surface. The strong bonding interaction of SO42− and Pb2+ ions leads to the reduced defect density, enhanced lattice stability, and robust photoluminescence quantum yield of perovskite film, which is confirmed by the density functional theory calculation. Moreover, the generated PbSO4 reduces the internal resistance and adjusts the band structure of perovskite film to enhance the carrier transport and injection balance. The PeLEDs based on PbSO4 decorated perovskite film exhibit enhanced operational lifetime and the maximum external quantum efficiency of 10.84%. [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]

Perovskite light-emitting diodes (PeLEDs) have promised as potential light source device for display. However, interfacial barrier generated from the mismatched band structure of charge transport layer and perovskite, which leads to the charge accumulation and low charge transport efficiency at the interface, resulting in an inferior performance of true-blue PeLEDs particularly. Herein, we show the interfacial band structure regulation realized by aqueous compatible alkali cations modification on poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate) (PEDOT:PSS), which achieves deeper highest occupied molecular orbital (HOMO) level for modified PEDOT:PSS benefiting charge transport at the interface, as well as reduces defect density of the perovskite film through improved crystallinity. Eventually, the champion device obtained on the true-blue PeLEDs based on Li cation modified PEDOT:PSS, exhibiting maximum luminance of 512.59 cd m−2, and a maximum external quantum efficiency (EQE) of 5.43% at 479 nm. Those performance values locate at the top ranking of similar devices. We modified PEDOT:PSS by different alkali cations. The HOMO level of the modified PEDOT:PSS films shift to deeper level that benefits the hole injection at the interface, thus enhances the performance of their true-blue PeLEDs with achieved maximum luminance of 512.59 cd m−2, and maximum EQE of 5.43% for the Li+ cations contained device. [Display omitted] • Interfacial band structure of PEDOT:PSS is regulated by alkali cations. • Deeper HOMO level of PEDOT:PSS benefits charge transport at the interface. • The champion true-blue PeLEDs exhibits luminance of 512.59 cd m−2 and EQE of 5.43%. [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]