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Inorganic CsPbI3 perovskite has great potential to fabricate deep‐red light‐emitting diodes (LEDs) owing to excellent color purity, thermal stability, and carrier mobility. However, fabricating high‐quality CsPbI3 thin films for high‐performance LEDs remains challenging. While it is demonstrated that hydrogen bonds between organic ammonium cations and molecule additives can lead to high‐quality organic–inorganic hybrid perovskite films, this method cannot be applied to CsPbI3 thin films due to the absence of hydrogen bonds between Cs+ ions and additives. In this study, an amorphous complex‐seed‐crystal growth process to fabricate high‐quality γ‐CsPbI3 cuboid crystallite thin films, is reported. During the initial annealing, the metastable intermediates formed crystal nucleate seeds and transformed into amorphous complex intermediates, maintaining stability at an elevated temperature for perovskite crystallization. With prolonged annealing, the amorphous complex around the nucleate seeds gradually converts to γ‐CsPbI3 perovskite, enabling us to fabricate CsPbI3 thin films with high crystallinity and orientation. The resulting deep‐red LEDs exhibit a peak external quantum efficiency (EQE) of 16.5% and a high maximum luminance of 3158 cd m−2. Moreover, the devices show significantly suppressed efficiency roll‐off, maintaining an EQE of 14.8% even under a high current density of 500 mA cm−2. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbI3 perovskite semiconductor is attractive for deep‐red light‐emitting diodes (LEDs) because of its high photoluminescence, good thermal stability, excellent charge transport, and solution processability. However, the metastable phase of optically active CsPbI3 hinders the fabrication of efficient and bright deep‐red LEDs. Herein, a multifunctional ionic ligand regulation strategy using (2‐hydroxy‐5‐methylphenyl) triphenyl‐phosphonium iodide and 3‐(N, N‐dimethyloctylammonio) propanesulfonate is reported to regulate the optically active CsPbI3 crystallization and thus obtain high‐quality γ‐CsPbI3 thin films. The high crystallinity and preferential orientation of γ‐CsPbI3 arise from the strong bonding between the ionic ligands and ionic lead halide clusters. The obtained γ‐CsPbI3 thin films also possess suppressed defect densities, high luminescence, and high stability. Using this high‐quality thin film, an efficient and bright deep‐red LED with a peak external quantum efficiency of 13.34% and a maximum luminance of 2110 cd m−2 is successfully fabricated. The operational lifetime of the fabricated LED (time to half of the initial brightness, T50) reaches up to 40 min under a high current density of 50 mA cm−2 (corresponding to the initial brightness of 200 cd m−2). [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbI3 perovskite is a promising emitter for deep‐red light‐emitting diodes (LEDs). However, presently fabricated CsPbI3 polycrystalline films are composed of island‐like polycrystals, encountering the problems of serious interface current leakage and low‐efficiency carrier radiative recombination. Here, a CsPbI3‐xBrx quantum dots (QDs) matrix encapsulated CsPbI3 polycrystal film is reported to address the low‐efficiency issue of island‐like CsPbI3 polycrystalline film applied in deep‐red LEDs. The developed QDs matrix encapsulation strategy has two benefits. One is the filling of void space in the island‐like CsPbI3 polycrystal film to suppress the interface current leakage. The other more important benefit is utilizing the strong carrier confinement effect of QDs to strengthen the formation of excitons in the composite film and thus improve the electroluminescence efficiency. Moreover, interesting grain growth is found between CsPbI3‐xBrx QDs and CsPbI3 polycrystals, which further enhances the exciton transfer effect brought by the QDs matrix and optoelectronic properties of the fabricated composite films. Based on the obtained high‐quality QDs/polycrystal composite films, efficient and bright deep‐red LEDs are achieved with a peak external quantum efficiency of 15.24% and a maximum luminance of 3691 cd m−2. [ABSTRACT FROM AUTHOR]

The production of photocatalytic materials with strong light absorption ability and high quantum efficiency by simple means is a long-term goal of photocatalytic technology. In this work, we have synthesized Cu doped ZnO nanoparticles by a facile sol-gel method. By introducing Cu impurities, it is shown that the excitons in ZnO have been efficiently separated into free carriers, leading to optimized photocatalytic performance. The surface amorphous layers of the nanoparticles grew thicker at the introduction of Cu atoms into ZnO lattice, which boosted the photocatalytic ability due to the increase of surface oxygen vacancy concentration. This finding provides a direct evidence of quasi-particle-free carrier conversion in Cu doped ZnO, as well as a guidance for fabricating high efficiency ZnO based nano-photocatalysts. In this manuscript, a Cu/ZnO nanocomposites were prepared by sol-gel method, with the doping of trace Cu ions into ZnO crystals and excess Cu ions on the surface of ZnO. Due to the presence of Cu doping in the ZnO nanoparticle during annealing, we have proven that the migration of the positively charged point defects could thicken the surface amorphous layer, which promote the photocatalytic performance due to the extraction of positive charge towards the surface.Besides, most importantly, the introducing of Cu atoms in ZnO lattice could effectively convert the bounded exciton into free carriers, the increase the charge degrees of freedom is expected to contribute the charge separation for participating the chemical reaction. Our finding reveals the co-contribution of quasi-particle/free carrier conversion and oxygen vacancies dynamics for benefiting the charge separation, which expect to be useful for designing high performance ZnO based photocatalyst. [ABSTRACT FROM AUTHOR]