Enhanced photoluminescence quantum efficiency and stability of water assisted CsPbBr3 perovskite nanocrystals

Broadband photodetectors from silane-passivated CsPbBr3 nanocrystals by ultrasound-mediated synthesis

Perovskite nanocrystals have excellent optical properties but suffer from environmental instability and production up-scaling which limit their commercial application. Here, we report the gram-scale ultrasound-mediated synthesis of silane passivated CsPbBr3 nanocrystals using (3-aminopropyl) triethoxysilane (APTS) as the primary surface ligand surface. The surface engineering endowed the CsPbBr3@SiOR NCs with extended environmental stability, a narrow emission bandwidth and a high photoluminescence quantum yield (PLQY > 75%). Thanks to these excellent optical properties, high-efficiency lateral and vertical photodetectors were fabricated. In particular, the layered vertical photodiode composed of ITO/Ga2O3/CsPbBr3/Au exhibited a broadband photoresponse from 350-700 nm with a responsivity peaking at 44.5.1 A W-1 and specific detectivity above 1013 Jones when illuminated at 470 nm wavelength and biased at +5 V. These results correspond to the best-in-class performance perovskite nanocrystal PD and confirm the extraordinary potential of CsPbBr3@SiOR for the development of efficient optoelectronic devices.

Surface Reconstruction of Lead-Free Perovskite Cs2Ag0.6Na0.4InCl6:Bi by Hydroxylation with Blue-Light-Excited Performance

Molecular surface reconfiguration strategies have been instrumental to performance improvements of halide perovskite photovoltaic applications in recent years. However, research into the optical properties of the lead-free double perovskite Cs₂AgInCl₆ on the complex reconstructed surface is still lacking. Here, blue-light excitation in double perovskite Cs₂Na_0.4Ag_0.6InCl₆ with Bi doping has been successfully achieved by excess KBr coating and ethanol-driven structural reconstruction. Ethanol drives the formation of hydroxylated Cs_2-yK_yAg_0.6Na_0.4In_0.8Bi_0.2Cl_6-yBr_y in the Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@xKBr interface layer. The hydroxyl group adsorbed on the interstitial sites of the double perovskite structure induces a transfer of local space electrons to the [AgCl₆] and [InCl₆] octahedral regions, enabling them to be excited with blue light (467 nm). The passivation of KBr shell reduces the non-radiative transition probability of excitons. Blue-light-excited flexible photoluminescence devices based on hydroxylated Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@16KBr are fabricated. The application of hydroxylated Cs₂Ag_0.6Na_0.4In_0.8Bi_0.2Cl₆@16KBr as down-shift layer in GaAs photovoltaic cell module can increase its power conversion efficiency by 3.34%. The surface reconstruction strategy provides a new way to optimize the performance of lead-free double perovskite.

CsPbBr3 and Cs4PbBr6 perovskite light-emitting diodes using a thermally evaporated host-dopant system

This article shows the results of fabricating a device through vacuum deposition by synthesizing a perovskite thin film in the powder form. Light emitting diodes (LEDs) were fabricated using a single-source and host-dopant system of the perovskite produced in the powder form. Both CsPbBr₃ and Cs₄PbBr₆ used in the host-dopant system were green, and the host was tris(8-quinolinolato) aluminum(III). It is confirmed that the display efficiency and optical characteristics are significantly improved by the dopant ratio. The 3%-doped CsPbBr₃ based LED shows a luminance of 9083 cd m^-2, 3.36% external quantum efficiency (EQE), and 96% photoluminescence quantum yield (PLQY) efficiency (for the undoped CsPbBr₃ LED, luminance: 844 cd m^-2/EQE: 1.93%/PLQY: 85%). The LED based on 5%-doped Cs₄PbBr₆ shows a luminance of 11 440 cd m^-2, an EQE of 6.27%, and 99% PLQY efficiency (for the undoped Cs₄PbBr₆ LED, luminance:1113 cd m^-2/EQE: 1.64%/PLQY: 93%). It is expected that the results of this research will contribute to the perovskite LED research performed by thermal evaporation in the future.

Synthesis and Applications of Halide Perovskite Nanocrystals in Optoelectronics

The perovskites used for optoelectronic devices have been more attractive during recent years due to their wide variety of advantages, such as their low cost, high photoluminescence quantum yield (PLQY), high carrier mobility, flexible bandgap tunability, and high light absorption ability. However, optoelectronic applications for traditional inorganic and organic materials present dilemmas due to their hardly tunable bandgap and instability. On the other hand, there are some more important benefits for perovskite nanocrystals, such as a size-dependent bandgap and the availability of anion exchange at room temperature. Therefore, perovskite NC-based applications are currently favored, offering a research direction beyond perovskite, and much research has focused on the stability issue and device performance. Thus, the synthesis and applications of perovskite NCs need to be thoroughly discussed for the future development of solar cells, light-emitting diodes, photodetectors, and laser research.

Moisture-Assisted near-UV Emission Enhancement of Lead-Free Cs4CuIn2Cl12 Double Perovskite Nanocrystals

Lead-based halide perovskite nanocrystals (NCs) are recognized as emerging emissive materials with superior photoluminescence (PL) properties. However, the toxicity of lead and the swift chemical decomposition under atmospheric moisture severely hinder their commercialization process. Herein, we report the first colloidal synthesis of lead-free Cs₄CuIn₂Cl₁₂ layered double perovskite NCs via a facile moisture-assisted hot-injection method stemming from relatively nontoxic precursors. Although moisture is typically detrimental to NC synthesis, we demonstrate that the presence of water molecules in Cs₄CuIn₂Cl₁₂ synthesis enhances the PL quantum yield (mainly in the near-UV range), induces a morphological transformation from 3D nanocubes to 2D nanoplatelets, and converts the dark transitions to radiative transitions for the observed self-trapped exciton relaxation. This work paves the way for further studies on the moisture-assisted synthesis of novel lead-free halide perovskite NCs for a wide range of applications.

Reveal the Humidity Effect on the Phase Pure CsPbBr3 Single Crystals Formation at Room Temperature and Its Application for Ultrahigh Sensitive X-Ray Detector

Generally, growing phase pure CsPbBr₃ single crystals is challenging, and CsPb₂ Br₅ or Cs₄ PbBr₆ by-products are usually formed due to the different solubilities of CsBr and PbBr₂ in the single solvent. Herein, the growth of high-quality phase pure CsPbBr₃ perovskite single crystals at room temperature by a humidity controlled solvent evaporation method is reported first. Meanwhile, the room temperature phase transition process from three dimensional (3D) cubic CsPbBr₃ to two dimensional (2D) layered tetragonal CsPb₂ Br₅ and the detailed mechanism induced by humidity are revealed. Moreover, compared with the organic-inorganic perovskite, the prepared CsPbBr₃ single crystals are much more stable under high humidity, which satisfies the long-term working conditions of X-ray detectors. The X-ray detectors based on CsPbBr₃ single crystals show a high sensitivity and a low detection limit of 1.89 μGy_air s^-1 , all of which meet the needs of medical diagnosis.

Ligand and adjuvant dual-assisted synthesis of highly luminescent and stable Cs4PbBr6 nanoparticles used in LEDs

We developed a new ligand and adjuvant dual-assisted room temperature colloidal method for the synthesis of highly luminescent and stable Cs₄PbBr₆ nanoparticles, in which acetone, oleamine (OM) and oleic acid (OA) were used as precursors, while water and dimethyl sulfoxide (DMSO) were used as adjuvants. In this process, we explored the influencing factors of process parameters (such as the amount of water, the standing time of precursors, and the molar ratio of raw materials), and found that Cs₄PbBr₆ synthesized by water + DMSO can not only change the morphology and promote crystallization but also improve the lattice strain, reduce the lattice defects and optimize the passivation effect, so as to improve the luminescence properties. Simultaneously, we also found that the pc-LED made of Cs₄PbBr₆ can still emit bright green light after 4344 h of operation, showing excellent stability and making it promising for solid-state lighting application. This method also provides an important reference value for solving the hydrolysis property of perovskites.

We developed a new room temperature colloidal method for the synthesis of highly luminescent and stable Cs₄PbBr₆ nanoparticles, in which acetone, oleamine and oleic acid were used as precursors, while water and dimethyl sulfoxide were used as adjuvants.

Investigating the property of water driven lead-free stable inorganic halide double perovskites

Lead free halide double perovskite materials, A₂BB́X₆ (where A, B and B́ are cations and X is a halide anion) have achieved considerable attention in the field of optoelectronic devices due to their high thermal along with the moisture stability and less toxicity as lead halide perovskites suffer from the stability and toxicity issues which inhibit them to be commercialized. Therefore, synthesis of low cost and stable perovskite materials are the main focus of perovskite family nowadays. Herein, we have reported lead free Cs₂AgBiCl₆ and Cs₂AgBiBr₆ double perovskite microcrystals in both organic and a mixture of the aqueous-organic medium. Our studies are not only eradicating the toxicity of lead but also explored towards the stability of perovskite materials in the aqueous medium. Morphology is investigated using SEM and TEM imaging along with the enhancement in emission peak by increasing the content of water.