Inorganic Ions Assisted the Anisotropic Growth of CsPbCl3 Nanowires with Surface Passivation Effect

Colloidal Perovskite Nanocrystals for Blue-Light-Emitting Diodes and Displays

The evolution of display technology toward ultrahigh resolution, high color purity, and cost-effectiveness has generated interest in metal halide perovskites, particularly colloidal perovskite nanocrystals (PeNCs). PeNCs exhibit narrow emission spectra, high photoluminescence quantum yields, and wide color gamuts, rendering them promising candidates for next-generation displays. Despite significant advancements in perovskite light-emitting diode (PeLED) technology, challenges remain regarding the efficiencies of PeNC-based blue LEDs. Addressing these challenges, including both inherent and external instabilities of PeNCs and operational instabilities of the devices, is important as they collectively impede the broader acceptance and utilization of PeNCs. Herein, a comprehensive overview of the syntheses of dimension- and composition-controlled blue colloidal PeNCs and critical factors influencing the performances of colloidal PeNC-based blue LEDs is provided. Moreover, the advancements of colloidal PeNC-based blue LEDs and challenges associated with the application of these LEDs are explored, and the potentials of these LEDs for application in next-generation displays are emphasized. This review highlights the path forward for the future development of PeNC-based blue LEDs.

One-Step Preparation of High-Stability CsPbX3/CsPb2X5 Composite Microplates with Tunable Emission

The core-shell structure is an effective means to improve the stability and optoelectronic properties of cesium lead halide (CsPbX3 (X = Cl, Br, I)) perovskite quantum dots (QDs). However, confined by the ionic radius differences, developing a core-shell packaging strategy suitable for the entire CsPbX3 system remains a challenge. In this study, we introduce an optimized hot-injection method for the epitaxial growth of the CsPb2X5 substrate on CsPbX3 surfaces, achieved by precisely controlling the reaction time and the ratio of lead halide precursors. The synthesized CsPbX3/CsPb2X5 composite microplates exhibit an emission light spectrum that covers the entire visible range. Crystallographic analyses and density functional theory (DFT) calculations reveal a minimal lattice mismatch between the (002) plane of CsPb2X5 and the (11 ¯ 0) plane of CsPbX3, facilitating the formation of high-quality type-I heterojunctions. Furthermore, introducing Cl- and I- significantly alters the surface energy of CsPb2X5's (110) plane, leading to an evolutionary morphological shift of grains from circular to square microplates. Benefiting from the passivation of CsPb2X5, the composites exhibit enhanced optical properties and stability. Subsequently, the white light-emitting diode prepared using the CsPbX3/CsPb2X5 composite microplates has a high luminescence efficiency of 136.76 lm/W and the PL intensity decays by only 3.6% after 24 h of continuous operation.

Water-stable perovskite CsPb2Br5/CdSe quantum dot-based photoelectrochemical sensors for the sensitive determination of dopamine

A heterojunction of CdSe quantum dots in situ grown on the perovskite CsPb2Br5 (CsPb2Br5/CdSe) for water-stable photoelectrochemical (PEC) sensing was simply synthesized using the hot-injection method. Due to the inherent built-in electric field and the matching band structure between CsPb2Br5 and CdSe, the CsPb2Br5/CdSe p-n heterojunction demonstrates enhanced photoelectrochemical properties. Accelerated interfacial charge transfer and increased electron-hole pair separation enable hydrolysis-resistant CsPb2Br5/CdSe sensors to exhibit heightened sensitivity with an ultra-low detection limit (0.0124 μM) and a wide linear range (0.4-303.9 μM) in subsequent dopamine detection. Moreover, the CsPb2Br5/CdSe sensors show excellent anti-interference ability, as well as remarkable stability and reproducibility in water solvent. It is noteworthy that this work is conducted in an aqueous environment, which provides an inspiring and convenient way for photoelectric and photoelectrocatalysis applications based on water-resistant perovskites.

YCl3-Substituted CsPbI3 Perovskite Nanorods for Efficient Red-Light-Emitting Diodes

Cesium lead iodide (CsPbI₃) perovskite nanocrystals (NCs) are a promising material for red-light-emitting diodes (LEDs) due to their excellent color purity and high luminous efficiency. However, small-sized CsPbI₃ colloidal NCs, such as nanocubes, used in LEDs suffer from confinement effects, negatively impacting their photoluminescence quantum yield (PLQY) and overall efficiency. Here, we introduced YCl₃ into the CsPbI₃ perovskite, which formed anisotropic, one-dimensional (1D) nanorods. This was achieved by taking advantage of the difference in bond energies among iodide and chloride ions, which caused YCl₃ to promote the anisotropic growth of CsPbI₃ NCs. The addition of YCl₃ significantly improved the PLQY by passivating nonradiative recombination rates. The resulting YCl₃-substituted CsPbI₃ nanorods were applied to the emissive layer in LEDs, and we achieved an external quantum efficiency of ~3.16%, which is 1.86-fold higher than the pristine CsPbI₃ NCs (1.69%) based LED. Notably, the ratio of horizontal transition dipole moments (TDMs) in the anisotropic YCl₃:CsPbI₃ nanorods was found to be 75%, which is higher than the isotropically-oriented TDMs in CsPbI₃ nanocrystals (67%). This increased the TDM ratio and led to higher light outcoupling efficiency in nanorod-based LEDs. Overall, the results suggest that YCl₃-substituted CsPbI₃ nanorods could be promising for achieving high-performance perovskite LEDs.

The metal doping strategy in all inorganic lead halide perovskites: synthesis, physicochemical properties, and optoelectronic applications

All inorganic perovskites CsPbX₃ (X = Cl, Br, I), rising stars of optical materials, have shown promising application prospects in optoelectronic and photovoltaic fields. However, some open issues still exist in these perovskites, like poor long-term stability, inevitable intrinsic defects and much nonradiative recombination, which greatly weakens their optical capability and seriously hinders their further development. The metal doping strategy, through the partial substitution of foreign ions for native ions, has gradually become an effective method for significantly enhancing the comprehensive properties of CsPbX₃. Whereas some previous studies have reported the impressive properties of metal-doped CsPbX₃, there is still a lack of a comprehensive review on the influences of metal doping on CsPbX₃. In this review, we aim to provide a systematic review of the latest achievements in metal-doped CsPbX₃, which focuses on their synthetic methods and the positive effects of metal doping on structure, optical properties, morphology control, carrier behavior and related optoelectronic and photovoltaic devices. Finally, we put forward a few opportunities and challenges about the further investigation of metal-doped perovskites, which may help researchers explore new research directions.

Copper-doping defect-lowered perovskite nanosheets for deep-blue light-emitting diodes

Mixed-halide blue perovskites CsPb(Br/Cl)₃ are considered promising candidates for developing efficient deep-blue perovskite light-emitting diodes (PeLEDs), but their low photoluminescence quantum yield (PLQY), environmental instability, and poor device performance gravely inhibit their future development. Here, we employ a heteroatomic Cu²⁺ doping strategy combined with post-treatment Br^- anion exchange to prepare high-performance deep-blue perovskites CsPb(Br/Cl)₃. The Cu²⁺ doping strategy significantly decreases the intrinsic chlorine defects, ensuring that the inferior CsPbCl₃ quantum dots are transformed into two-dimensional nanosheets with enhanced violet photoluminescence and increased exciton binding energy. Further, with the post-treatment Br^- anion exchange, the as-prepared CsPb(Br/Cl)₃ nanosheets with more radiation recombination and less ion migration present an enhanced PLQY of 94% and better humidity stability of 30 days. Based on the optimized CsPb(Br/Cl)₃, we fabricated deep-blue PeLEDs with luminescence emission at 462 nm, a maximum luminance of 761 cd m^-2, and a current density of 205 mA cm^-2. This work puts forward a feasible synthesis strategy to prepare efficient and stable mixed-halide blue perovskite CsPb(Br/Cl)₃ and related blue PeLEDs, which may promote the further application of mixed-halide perovskites in the blue light range.

Highly-stable tin-based perovskite nanocrystals produced by passivation and coating of gelatin

Lead-halide perovskite nanocrystals (NCs) are limited in commercial applications due to their high lead content. Developing lead-free perovskite NCs becomes a new choice. Among them, the tin-halide perovskite NCs exhibit the excellent photoelectric conversion efficiency, but has worse stability. Herein we describe an effective approach to the preparation of highly-stable all-inorganic tin-based perovskite NCs by using gelatin via interfacial passivation and coating, which leads to the retention of 77.46% of photoluminescence intensity even after the dispersion of the NCs in water for 3 d. The results show that gelatin form a "rich ligand" state on NC surface, such as amino-Sn, carboxylate-Sn and halogen-ammonium hydrogen-bonding interactions. The amino-Sn coordination would be replaced by carboxylate-Sn coordination when NCs are dispersed in polar-media. Meanwhile, gelatin is imparted excellent anti-mildew properties by NCs, which ensures long-lasting effect to NCs. This will promote the stability and sustainable development of the perovskite device.

Photodetector Based on Spontaneously Grown Strongly Coupled MAPbBr3/N-rGO Hybrids Showing Enhanced Performance

Recently, metal-halide perovskites have emerged as a candidate for optoelectronic applications such as photodetectors. However, the poor device performance and instability have limited their future commercialization. Herein, we report the spontaneous growth of perovskite/N-rGO hybrid structures using a facile solution method and their applications for photodetectors. In the hybrid structures, perovskites were homogeneously wrapped by N-rGO sheets through strong hydrogen bonding. The strongly coupled N-rGOs facilitate the charge carrier transportation across the perovskite crystals but also distort the surface lattice of the perovskite creating a potential barrier for charge transfer. We optimize the addition of N-rGO in the hybrid structures to balance interfacial structural distortion and the intercrystal conductivity. High-performance photodetection up to 3 × 10⁴ A/W, external quantum efficiency exceeding 10⁵%, and detectivity up to 10¹² Jones were achieved in the optimal device with the weight ratio between perovskites and N-rGO to be 8:1.5. The underlying mechanism behind the optimal N-rGO addition ratio in the hybrids has also been rationalized via time-resolved spectroscopic studies as a reference for future applications.