Search

Lead halide perovskite quantum dots (LHP QDs) emerge as versatile photonic sources in electroluminescence and laser devices. Their applications in optoelectronic devices are hindered by surface distortion and ligand stripping during the purification process. In addition, the device performance roll‐off suffers from the ultrafast non‐radiative Auger recombination (AR). To address these issues, herein, CsPbBr3 QDs are prepared with sizes ranging from 6.5 to 9.2 nm and the universal surface repairing strategy is proved to efficiently increase the biexciton lifetime and quantum yield up to 1.4 and 3 times, respectively. The strategy provides a PbBrx rich surface and strong binding didodecyldimethylammonium bromide (DDAB) ligands to achieve near‐unity photoluminescence efficiency, which significantly improves their stability against anti‐solvents and aging in ambient conditions. A single‐mode laser device is realized by self‐assembling the QDs into superlattice as optical microcavity, with low threshold of 9.45 µJ cm−2, quality factor of 2187 and ultrafast lifetime of 3.22 ps. The superlattice laser is demonstrated as an optical encoder with large coding bandwidth of 0.133 THz. This work proposes new insight into the non‐radiative AR process in these single‐component CsPbBr3 QDs, and will pave the way for optoelectronic devices working in intense conditions. [ABSTRACT FROM AUTHOR]

Physically unclonable functions (PUFs) have emerged as the most effective method against counterfeiting, leveraging the intrinsic randomness of objects to avoid data replication. However, despite their efficacy, the complexity and high cost of most PUF‐based counterfeiting labels hinder their practical application. Here, a high‐capacity PUF label based on vertically aligned perovskite nanowire (NW) arrays is demonstrated. The NW arrays are conveniently constructed using a low‐cost solution process using an anodized aluminum oxide template. Each pixel within the label is composed of closely packed CsPbBr3 NW arrays of different lengths, resulting in varied lasing signals. The collected signal of each pixel emerged from the lasing output of the NW arrays, generating high‐density and nonuniform multiple‐mode lasing to facilitate information encoding. A quaternary encoding mechanism is used to encode the number of laser modes per pixel. Impressively, it exhibits a mapping resolution of 1600 pixels within 400 µm2, achieving an impressive encoding capacity (1.97 × 10963) and a pixel density (4 bits µm−2) in this compact area. This work shows a promising approach for anticounterfeiting applications because of its simplicity, low cost, and high encoding capacity. [ABSTRACT FROM AUTHOR]

Optical coding is widely applied in communication and data processing fields due to its practical and powerful characteristics, such as high transmission rate and operational convenience. However, improvements in the loading information capacity of optical encoders always result in increased energy consumption. It is a challenge to realize an optical encoder that combines energy savings, high bandwidth, and miniaturization. Here, both the concept and the demonstration of a perovskite sub‐micro‐encoder with an 84% energy‐saving efficiency and a tunable bandwidth of up to 200 GHz are reported. The way to code the radiative dynamics of the light source allows for the reduction of unnecessary energy consumption from the initial stage through the control of the radiation core. Moreover, the miniature encoder generates code sequences of good coherence, stimulating the development of perovskite‐based optical microchips for ultrafast information processing. [ABSTRACT FROM AUTHOR]

Cavity‐enhanced superfluorescence (CESF) in quantum dot (QD) system is an ultrafast and intense lasing generated by combination of quantum coupling effect and optically stimulated amplification effect, which can provide a new idea for realizing high quality blue light sources and address the limitation of conventional inefficient blue light sources. Modifying halide composition is a straightforward method to achieve blue emission in perovskite QD system. However, the spectral instability introduced by photoinduced halide phase segregation and low coupling efficiency between QDs and optical cavities make it challenging to achieve stable blue CESF in such halide‐doped QD system. Herein, long‐range‐ordered, densely packed CsPbBr2Cl QD‐assembled superlattice microcavities in which the two core issues can be appropriately addressed are developed. The QD superlattice structure facilitates excitonic delocalization to decrease exciton‐phonon coupling, thus alleviating photoinduced phase segregation. By combination of theoretical analysis and temperature‐dependent photoluminescence (PL) measurements, the underlying photoinduced phase segregation mitigation mechanism in mixed halide superlattices is clarified. Based on the CsPbBr2Cl QD superlattices with regularly geometrical structures, in which the gain medium can be strongly coupled to the naturally formed microcavity, stable and ultrafast (3 ps) blue CESF with excellent optical performance (threshold ≈33 µJ cm−2, quality factor ≈1900) is realized. [ABSTRACT FROM AUTHOR]

Single perovskite alloy micro‐nano structure capable of emitting multi‐wavelength tunable lasing is desirable for its potential application in highly integrated photonic devices. However, owing to the soft and dynamic crystal lattice of perovskite and the low mobility energy of halide anion, it is still a challenge to obtain alloy micro‐nano structures with a stable bandgap gradient. Herein, based on the highly ordered superlattice consisting of well‐separated individual quantum dots and precise anion exchange strategy, a single perovskite alloy superlattice is obtained with a widely tunable bandgap. The photoluminescence (PL) spectra results indicate that the stability of the bandgap difference of the alloy superlattice sample is approximately 10 times higher than that of the previously reported perovskite single‐crystal alloy nanowires. By combination of quantitative study based on confocal PL measurements and theoretical calculations, the kinetics and atomic‐scale anion exchange mechanism are analyzed, the latter being responsible for the formation of stable bandgap gradient in the alloy superlattice. Multi‐wavelength lasing is further realized in single alloy superlattice. In addition, carrier transportation dynamics reveals the energy‐transfer process in the alloy superlattice, explaining the difficulties of realizing multicolor lasing. The work provides a new approach to solving problems in the field of stable multicolor microlasers. [ABSTRACT FROM AUTHOR]

Figuring out the inner mechanism of lattice distortion and unstable factors of inorganic perovskite nanocrystals in solvents is essential for fundamental studies and applications in photonic devices. Traditional research results simply ascribed the unstable factor to solvent polarity, which in fact are insufficient and inaccurate to explain some phenomena. Here, we propose a molecular level mechanism that the crucial cause for the instability of perovskite nanocrystals in solutions is the competition between complex bond energies in colloidal nanocrystals system. In combination with molecular dynamics simulations and first principle calculations, the kinetic process of lattice distortion and self‐assembly of perovskite nanocrystals is revealed in solutions. By tailoring the relative magnitude of the hydrogen bond energy between ligand ammonium ion and halogen, the van der Waals force between the ligands of adjacent nanocrystals and the bond energy between lead atom and halogen, nanocrystal arrays and single‐crystalline nanowires based on all‐inorganic perovskite nanocrystals can be freely obtained. Moreover, the polarization properties of the obtained nanowires are studied, which are related to their formation process. [ABSTRACT FROM AUTHOR]

Perovskites—energy‐conversion materials with light‐absorbing and electronic transport properties—have shown excellent features for developing photovoltaic devices and novel light sources. It is an open challenge to extend the application of perovskites, such as to the field of ultrafast information coding. This work demonstrates a terahertz coding of optical polarization degree based on a metal halide perovskite nanostructure. Sub‐micrometer spheres of all‐inorganic CsPbBr3 perovskite are fabricated with high quality and stability. By employing this perovskite nanostructure, the ultrafast coding of degree of linear polarization (DLP) is achieved with a tunable bandwidth of up to 0.1 THz. Moreover, the DLP coding can be combined with the coding of another parameter, i.e., the shape of the lasing pulse, which improves the high‐bandwidth encoder from binary to ternary. The all‐photonic miniature encoder generates multiple‐parameter THz code sequences, stimulating the development of perovskite‐based microdevices for ultrafast information processing. [ABSTRACT FROM AUTHOR]

Perovskites—compounds with the CaTiO3-type crystal structure—show outstanding performance in photovoltaics and multiparameter optical emitters due to their large oscillator strength, strong solar absorption, and excellent charge-transport properties. However, the ability to realize and control many-body quantum states in perovskites, which would extend their application from classical optoelectronic materials to ultrafast quantum operation, remains an open research topic. Here, we generate a cooperative quantum state of excitons in a quantum dot ensemble based on a lead halide perovskite, and we control the ultrafast radiation of excitonic quantum ensembles by introducing optical microcavites. The stimulated radiation of excitonic quantum ensemble in a superlattice microcavity is demonstrated to not be limited by the classical population-inversion condition, leading to a picosecond radiative duration time to dissipate all of the in-phase dipoles. Such a perovskite-assembly superlattice microcavity with a tunable radiation rate promises potential applications in ultrafast, photoelectric-compatible quantum processors. The realization and control many-body quantum states in perovskites would extend their application to ultrafast quantum operation. Here, the authors generate a cooperative quantum state of excitons in a lead halide perovskite quantum dot ensemble and control the ultrafast radiation through optical microcavites. [ABSTRACT FROM AUTHOR]

Rubidium lead halides (RbPbX3), an important class of all‐inorganic metal halide perovskites, are attracting increasing attention for photovoltaic applications. However, limited by its lower Goldschmidt tolerance factor t≈0.78, all‐inorganic RbPbBr3 has not been reported. Now, the crystal structure, X‐ray diffraction (XRD) pattern, and band structure of perovskite‐phase RbPbBr3 has now been investigated. Perovskite‐phase RbPbBr3 is unstable at room temperature and transforms to photoluminescence (PL)‐inactive non‐perovskite. The structural evolution and mechanism of the perovskite–non‐perovskite phase transition were clarified in RbPbBr3. Experimentally, perovskite‐phase RbPbBr3 was realized through a dual‐source chemical vapor deposition and annealing process. These perovskite‐phase microspheres showed strong PL emission at about 464 nm. This new perovskite can serve as a gain medium and microcavity to achieve broadband (475–540 nm) single‐mode lasing with a high Q of about 2100. [ABSTRACT FROM AUTHOR]

We present the nonlinear optical properties of CsPb(Br/I)3 perovskite quantum dots (QDs) with high crystallinity. The perovskite QDs show better two-photon absorption response than the traditional metal chalcogenide QDs. And, the photoluminescence peak of the halogen vacancies in perovskite nanocrystals was experimentally observed for the first time. [ABSTRACT FROM AUTHOR]

The exploration of cooperative states in many‐body systems is a key research area. It focuses on superfluorescence (SF), a phenomenon linked with radiative dipole coupling, and its intersection with classical lasing effects. This produces a unique lasing‐field‐hybrid cooperative dipole (LCD) state through optical cavity‐enhanced superfluorescence (CESF). A coherent energy transfer is demonstrated between two such states within a perovskite quantum dot (QD) superlattice. This results in competitive luminescence timing dynamics. The findings reveal that stimulated energy transfer occurs when two cooperative cavity‐exciton states coexist, controllable via a dual‐pulse pump technique. This understanding is vital for advancing quantum phenomena knowledge and enhancing optoelectronic devices. [ABSTRACT FROM AUTHOR]