Search Results (32)

This work reports the results of a study on the optical, morphological, and structural properties of cesium lead bromide iodide mixed perovskite thin films (CsPbBr_3−xI_x), synthesized by sequential evaporation of precursors (CsBr, PbBr₂, PbI₂). First, the deposition conditions were optimized to obtain thin films predominantly composed of the pure CsPbBr₃ phase. Subsequently, the influence of partial substitution of Br⁻ by I⁻ on the film properties was investigated. Particular emphasis was placed on evaluating the effect of partial Pb²⁺ substitution by Zn²⁺ on the optical, morphological, electronic, and structural properties using optical transmittance, photoluminescence, scanning electron microscopy (SEM), X-ray diffraction (XRD), Urbach energy analysis, and density functional theory (DFT) calculations. Zn²⁺-doped CsPbBr_3−xI_x films were prepared by evaporating a ZnBr₂ layer onto the pre-deposited PbBr₂/PbI₂ precursor layers. It was found that Zn²⁺-doped inorganic CsPbBr_3−xI_x perovskite films exhibit enhanced crystallinity and improved surface morphology. Additionally, photoluminescence characterization confirms that non-radiative recombination decreases significantly, apparently due to a reduction in intrinsic defect density. The effect of Zn²⁺ doping on the power conversion efficiency of carbon-based planar solar cells was also evaluated. Collectively, Urbach energy, photoluminescence, and SEM analyses revealed that the optimal Zn²⁺ doping range for CsPbBr_3−xI_x perovskite films is ≤5%. Full article

Flexible X-ray detectors have emerged as a promising technology for portable medical imaging and wearable electronics, yet their manufacturing remains constrained by the competing requirements of device performance, mechanical conformability, and production scalability. Conventional solution-based deposition methods fail to yield high-quality perovskite thick films with uniform morphology, while vacuum evaporation techniques are limited by exorbitant operational costs and low throughput. Herein, we report an optimized solution-processed vacuum evaporation strategy that enables the fabrication of high-quality perovskite films (~1 μm thick) on flexible polyethylene naphthalate (PEN) substrates at a low processing temperature of 100 °C. By incorporating tailored additives into the precursor solution and precisely modulating the vapor-phase conversion kinetics, we achieved significant improvements in film density, crystallinity, and morphological uniformity. Systematic investigations were conducted to elucidate the structure–property relationships across three material systems: pure methylammonium lead iodide (MAPbI₃), halogen-doped methylammonium lead iodide-bromide (MAPb(IBr)₃), and synergistic cation-halogen engineered cesium-methylammonium lead iodide-bromide (CsMAPb(IBr)₃). The optimized flexible PIN-type X-ray detector based on CsMAPb(IBr)₃ exhibited exceptional performance metrics, including a dark current density as low as 5.2 nA cm⁻² and an X-ray sensitivity of up to 1.43 × 10⁴ μC·Gy_air⁻¹·cm⁻². Remarkably, the device retained over 95% of its initial performance after 400 bending cycles with a bending radius of 6 mm, demonstrating outstanding mechanical robustness and operational durability. This work establishes a viable, cost-effective technical route for the scalable production of high-performance flexible X-ray detectors, addressing critical challenges in the advancement of next-generation portable imaging technologies. Full article

The persistent operational instability of all-inorganic cesium lead halide (CsPbX₃) perovskite nanocrystals (NCs) has hindered their integration into white-light-emitting diodes (WLEDs). This study introduces a transformative approach by engineering a phase transition from CsPbBr₃ NCs to zirconium bromide (ZrBr₄)-stabilized hexagonal nanocomposites (HNs) through a modified hot-injection synthesis. Structural analyses revealed that the ZrBr₄-mediated phase transformation induced a structurally ordered lattice with minimized defects, significantly enhancing charge carrier confinement and radiative recombination efficiency. The resulting HNs achieved an exceptional photoluminescence quantum yield (PLQY) of 92%, prolonged emission lifetimes, and suppressed nonradiative decay, attributed to effective surface passivation. The WLEDs with HNs enabled a breakthrough luminous efficiency of 158 lm/W and a record color rendering index (CRI) of 98, outperforming conventional CsPbX₃-based devices. The WLEDs exhibited robust thermal stability, retaining over 80% of initial emission intensity at 100 °C, and demonstrated exceptional operational stability with negligible PL degradation during 50 h of continuous operation at 100 mA. Commission Internationale de l’Éclairage (CIE) coordinates of (0.35, 0.32) validated pure white-light emission with high chromatic fidelity. This work establishes ZrBr₄-mediated HNs as a paradigm-shifting material platform, addressing critical stability and efficiency challenges in perovskite optoelectronics and paving the way for next-generation, high-performance lighting solutions. Full article

The material family halide perovskites has been critical in recent room-temperature radiation detection semiconductor research. Cesium lead bromide (CsPbBr₃) is a halide perovskite that exhibits characteristics of a semiconductor that would be suitable for applications in various fields. In this paper, we report on the correlations between material purification and crystal material properties. Crystal boules of CsPbX₃ (where X = Cl, Br, I, or mixed) were grown with the Bridgman growth method. We describe in great detail the fabrication techniques used to prepare sample surfaces for contact deposition and sample testing. Current–voltage measurements, UV–Vis and photocurrent spectroscopy, as well as photoluminescence measurements, were carried out for material characterization. Bulk resistivity values of up to 3.0 × 10⁹ Ω∙cm and surface resistivity values of 1.3 × 10¹¹ Ω/□ indicate that the material can be used for low-noise semiconductor detector applications. Preliminary radiation detectors were fabricated, and using photocurrent measurements we have estimated a value of the mobility–lifetime product for holes (μτ)_h of 2.8 × 10⁻⁵ cm²/V. The results from the sample testing can shed light on ways to improve the crystal properties for future work, not only for CsPbX₃ but also other halide perovskites. Full article

Regulating the nucleation temperature and growth rates during inverse temperature crystallization (ITC) is vital for obtaining high-quality perovskite single crystals via this technique. Precise control over these parameters enables growing crystals optimized for various optoelectronic devices. In this study, it is demonstrated that incorporating a 1-butyl-3-methylimidazolium bromide (BMIB) ionic liquid into the precursor solution of cesium lead bromide (CsPbBr₃) brings about a dual enhancement effect. This includes a reduction in nucleation temperature from 85 °C to 65 °C and a significant improvement in both optoelectronic characteristics and crystal properties. The CsPbBr₃ single crystals grown using ITC with BMIB added (method (2)) demonstrate improved chemical and physical properties (crystallinity, lattice strain, nonradioactive recombination, and trap density) compared to CsPbBr₃ single crystals produced through conventional 85 °C ITC alone (method (1)). The exceptional quality of CsPbBr₃ single crystals produced with the inclusion of BMIB allowed for the development of a highly responsive optoelectronic device, demonstrating heightened sensitivity to green light. The findings of this investigation reveal that the growth of perovskite single crystals assisted by ionic liquid exerts a substantial impact on the characteristics of the crystals. This influence proves advantageous for the development of optoelectronic devices based on single crystals. Full article

We conducted experiments utilizing the scattering effect of zinc oxide (ZnO) to enhance the photoluminescence (PL) intensity of cesium lead bromide (CsPbBr₃) perovskite quantum dots (QDs). This study involved investigating the method for creating a CsPbBr₃ and ZnO mixture and determining the optimal mixing ratio. A mixture dispersion of CsPbBr₃ and ZnO, prepared at a 1:0.015 weight ratio through shaking, was fabricated into a film using the spin coating method. The PL intensity of this film showed a relative increase of 20% compared to the original CsPbBr₃ QD film without ZnO. The scattering effect of ZnO was confirmed through ultraviolet-visible (UV-Vis) absorption and transient PL experiments, and a long-delayed exciton lifetime was observed in the optimized mixture dispersion thin film. The morphology of the fabricated film was characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). For the CsPbBr₃-ZnO mixture (1:0.0015) film, crystal domains of approximately 10 nm were observed using TEM. Through AFM analysis, an excellent film roughness of 4.6 nm was observed, further confirming the potential of perovskite QD/ZnO composite films as promising materials for enhanced photoconversion intensity. In future studies, applying this method to other perovskite materials and metal oxides for the optimization of photoconversion composite materials is expected to enable the fabrication of highly efficient perovskite QD/metal oxide composite films. Full article

Morphology plays a crucial role in defining the optical, electronic, and mechanical properties of halide perovskite microcrystals. Therefore, developing strategies that offer precise control over crystal morphology during the growth process is highly desirable. This work presents a simple scheme to simultaneously grow distinct geometries of cesium lead bromide (CsPbBr₃) microcrystals, including microrods (MR), microplates (MP), and microspheres (MS), in a single chemical vapor deposition (CVD) experiment. By strategically adjusting precursor evaporation temperatures, flux density, and the substrate temperature, we surpass previous techniques by achieving simultaneous yet selective growth of multiple CsPbBr₃ geometries at distinct positions on the same substrate. This fine growth control is attributed to the synergistic variation in fluid flow dynamics, precursor substrate distance, and temperature across the substrate, offering regions suitable for the growth of different morphologies. Pertinently, perovskite MR are grown at the top, while MP and MS are observed at the center and bottom regions of the substrate, respectively. Structural analysis reveals high crystallinity and an orthorhombic phase of the as-grown perovskite microcrystals, while persistent photonic lasing manifests their nonlinear optical characteristics, underpinning their potential application for next-generation photonic and optoelectronic devices. Full article

Among all the inorganic perovskites, cesium lead bromide (CsPbBr${}_3$) has gained significant interest due to its stability and remarkable optoelectronic/photoluminescence properties. Because of the influence of deposition techniques, the experimental conditions that play a key role in each need to be addressed. In this context, we present CsPbBr${}_3$ films grown by pulsed laser deposition (PLD) and discuss the impact of oxygen stemming from their growth under a reduced vacuum, i.e., as the background atmosphere, rather than from post-growth exposure. In detail, stoichiometric mechano-chemically synthesized targets were prepared for deposition by nanosecond-PLD ($\lambda$ = 248 nm, $\tau$ = 20 ns, room temperature, fluence of 1 J/cm${}^2$) to produce slightly Br-deficient CsPbBr${}_3$ films under different background pressure conditions (P${}_0$ = 10${}^{-4}$, 10${}^{-2}$ Pa). The characterization results suggest that the presence of oxygen during the deposition of CsPbBr${}_3$ can advantageously passivate bromide-vacancy states in all the film thicknesses and reduce losses from emissions. Overall, our findings shed light on the critical role of oxygen, under conditions in which we ruled out other effects related to air exposure, and provide valuable guidelines for potential applications in various optoelectronic devices. Full article

In recent years, all-inorganic cesium lead bromide (CsPbBr₃) perovskites have garnered considerable attention for their prospective applications in green photonics and optoelectronic devices. However, the development of efficient and economical methods to obtain high-quality micron-sized single-crystalline CsPbBr₃ microplatelets (MPs) has become a challenge. Here, we report the synthesis of CsPbBr₃ MPs on Si/SiO₂ substrate by optimizing the ultrafast antisolvent method (FAS). This technique is able to produce well-dispersed, uniformly sized, and morphologically regular tetragonal phase single crystals, which can give strong green emission at room temperature, with excellent stability and excitonic character. Moreover, the crystals demonstrated lasing with a whispering gallery mode with a low threshold. These results suggest that the single-crystalline CsPbBr₃ MPs synthesized by this method are of high optical quality, holding vast potential for future applications in photonic devices. Full article

Room temperature (RT) synthesis of the ternary cesium lead bromide CsPbBr₃ quantum dots with oleic acid and oleylamine ligands was developed by Zeng and coworkers in 2016. In their works, the supersaturated recrystallization (SR) was adopted as a processing method without requiring inert gas and high-temperature injection. However, the oleic acid ligand for haloplumbate is known to be relatively unstable. Hence, in this work, we employed the eco-friendly olive oil to replace the oleic acid portion for the SR process at RT. Resultantly, we found that the cube-shaped nanocrystal has a size of ~40–42 nm and an optical bandgap of ~2.3 eV independent of the surface ligands, but the photoluminescence lifetime (τ_av) and crystal packing are dependent on the ligand species, e.g., τ_av = 3.228 ns (olive oil and oleylamine; here less ordered) vs. 1.167 ns (oleic acid and oleylamine). Importantly, we explain the SR mechanism from the viewpoint of the classical LaMer model combined with the solvent engineering technique in details. Full article

For the first time, the synthesis, luminescent and structural properties of stable perovskite-type (Cs_1−xRb_x)₄PbBr₆ (R = Cs, Rb) nanocrystals are shown. In the absence of rubidium, Cs₄PbBr₆ and CsPbBr₃ perovskite crystals precipitate in the ZnO–Na₂O–B₂O₃–GeO₂ glass matrix. With ascending rubidium content, the precipitation of (Cs,Rb)₄PbBr₆ nanocrystals is replaced by the Rb₄PbBr₆ nanocrystals nucleation. Nucleated nanocrystals exhibit an intense green luminescence. With an increase of the rubidium content, the luminescence maximum shifts to the blue region, the luminescence quantum yield increases from 28 to 51%, and the average decay time increases from 2 to 8 ns. Several assumptions have been made about the nature of the green luminescence of perovskite-like Cs₄PbBr₆ and (Cs,Rb)₄PbBr₆ crystals in glasses. It is concluded that the most probable cause is the impurity inclusions of CsPbBr₃ and (Cs,Rb)PbBr₃ crystals. Full article

Halide perovskite light-emitting diodes (PeLEDs) have attracted great attention because of their superior optical properties, such as extremely high photoluminescence (quantum yield up to nearly 100%) of active layers with tunable wavelengths over the entire visible spectral range. With a suitable modification of halide perovskites, carrier transport materials, and their interfaces, external quantum efficiencies exceeding 10%, 25%, and 20% have been achieved for blue-colored (465 nm), green-colored (512 nm), and red-colored (640 nm) LEDs, respectively. Many strategies for pursuing high performances of devices have been successfully demonstrated, among which ligand engineering has always played an important role in the active layer. Herein, we present a perspective to illustrate the effects and roles of the ligands in cesium lead bromide light-emitting diodes. This perspective is mainly classified into three parts: (1) ligands for CsPbBr₃ LEDs could improve radiative recombination of perovskites and contribute to better efficiency of LEDs; (2) ligands could confine CsPbBr₃ growth for blue emission of LEDs; (3) stabilities of materials and devices become better with ligand engineering. Finally, the summary and perspective on PeLEDs are highlighted and possible solutions are provided. Full article

Inorganic halide perovskites of the type AMX₃, where A is an inorganic cation, M is a metal cation, and X is a halide anion, have attracted attention for optoelectronics applications due to their better optical and electronic properties, and stability, under a moist and elevated temperature environment. In this contribution, the electronic, optical, thermoelectric, and elastic properties of cesium lead bromide, CsPbBr₃, and Rb-doped CsPbBr₃, were evaluated using the density functional theory (DFT). The generalized gradient approximation (GGA) in the scheme of Perdew, Burke, and Ernzerhof (PBE) was employed for the exchange–correlation potential. The calculated value of the lattice parameter is in agreement with the available experimental and theoretical results. According to the electronic property results, as the doping content increases, so does the energy bandgap, which decreases after doping 0.75. These compounds undergo a direct band gap and present an energies gap values of about 1.70 eV (x = 0), 3.76 eV (x = 0.75), and 1.71 eV (x = 1). The optical properties, such as the real and imaginary parts of the dielectric function, the absorption coefficient, optical conductivity, refractive index, and extinction coefficient, were studied. The thermoelectric results show that after raising the temperature to 800 K, the thermal and electrical conductivities of the compound RbxCs_1−xPbBr₃ increases (x = 0, 0.25, 0.50 and 1). Rb_0.75Cs_0.25PbBr₃ (x = 0.75), which has a large band gap, can work well for applications in the ultraviolet region of the spectrum, such as UV detectors, are potential candidates for solar cells; whereas, CsPbBr₃ (x = 0) and RbPbBr₃ (x = 1), have a narrow and direct band gap and outstanding absorption power in the visible ultraviolet energy range. Full article

In this work, acetone gas sensors were fabricated using pre-annealing metal oxide zinc oxide (pa-ZnO)-doped perovskite cesium lead bromide (CsPbBr₃). The ZnO nanopowder, before it was doped into CsPbBr₃ solution, was first put into a furnace to anneal at different temperatures, and formed the pa-ZnO. The properties of pa-ZnO were different from ZnO. The optimized doping conditions were 2 mg of pa-ZnO nanopowder and pre-annealing at 300 °C. Under these conditions, the highest sensitivity (gas signal current-to-air background current ratio) of the ZnO-doped CsPbBr₃ perovskite acetone sensor was 1726. In addition, for the limit test, 100 ppm was the limit of detection of the ZnO-doped CsPbBr₃ perovskite acetone sensor and the sensitivity was 101. Full article

It is becoming increasingly important to develop innovative self-powered, low-cost, and flexible sensors with the potential for structural health monitoring (SHM) applications. The mechanoluminescence (ML)-perovskite sensor is a potential candidate that combines the light-emitting principles of mechanoluminescence with the light-absorbing properties of perovskite materials. Continuous in-situ SHM with embedded sensors necessitates long-term stability. A highly stable cesium lead bromide photodetector with a carbon-based electrode and a zinc sulfide (ZnS): copper (Cu) ML layer was described in this article. The addition of a magnesium iodide (MgI₂) interfacial modifier layer between the electron transport layer (ETL) and the Perovskite interface improved the sensor’s performance. Devices with the modified structure outperformed devices without the addition of MgI₂ in terms of response time and impact-sensing applications. Full article