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The perovskite crystals formed by methylammonium lead iodide (MAPbI3) have garnered growing interest owing to their exceptional photovoltaic capabilities, economical production process, and ability to be processed in solution. A multitude of techniques have been devised to produce dense and uniform perovskite thin coatings, which are critical for the proper functioning of electronic devices. In order to promote the development of CH3NH3PbI3 perovskite thin films that are uniform, dense, and exceptionally smooth, we present an additive-assisted method utilizing Copper zinc tin sulfide Cu2ZnSnS4 (CZTS) nanoparticles. The surface, optical, morphological, and structural properties were subsequently determined. The mechanisms by which the additive improves the quality of the material during the formation of CH3NH3PbI3 perovskite films are elucidated in this study. These processes are postulated to characterize the crystallization of the films. Using this beneficial technique, a high-quality CH3NH3PbI3 film with a grain size significantly larger than 1.6 μm was effectively manufactured. Additionally, the doping process resulted in enhancements in both absorption and photoluminescence intensity. The addition of CZTS NPs elevated the crystal structures and morphologies of the CH3NH3PbI3 layer to a degree that was comparatively favorable. This was evidenced by the crystallite size of 83 nm and an optical bandgap (Eg) of 1.63 eV, both of which attest to the enhanced quality of the film. With the structure of glass/FTO/TiO2/CH3NH3PbI3:CZTS NPs/spiro-oMeTAD/Au ,the power conversion efficiency (PCE) of the best cell was 15.13% with a fill factor of 66.07%. The results of this study indicate that doping CH3NH3PbI3 solar cells with CZTS NPs is a dependable method for enhancing photovoltaic performance and promoting crystal growth. [ABSTRACT FROM AUTHOR]

The switch to sustainable power generation sources has gained substantial spotlight due to the essential need to decrease fossil fuels dependence, and alleviate climate change issues. This research aims to explore the first principle calculations for geometrical structure, enthalpy of formation, electronic structure behavior, optical spectra, and photocatalytic performance of the clean new Iodine-based triple perovskite compounds A3B2I9 (A = Rb or Cs, and B = Sb or Bi) using FP-LAPW method based on the density functional theory implemented in Wien2K software. The outcomes prove that these triple perovskite compounds can be formed spontaneously under standard conditions, because they are thermodynamically stable. Moreover, the electronic band structure shows an indirect semiconductor behavior of all studied compounds. Further, the optical spectra highlights that all studied compounds have high visible light absorption due to their suitable forbidden band values [1.8 eV–2.369 eV] which facilitate efficient electron–hole pairs generation maximizing the conversion of light into electrical energy. In addition, all studied compounds are satisfied the limits necessary to split water and then to produce hydrogen. Consequently, these compounds are most likely to be used as Lead-free perovskites in various optoelectronic applications, especially solar cells and hydrogen production from water splitting. [ABSTRACT FROM AUTHOR]

In this study, we investigated the optoelectronic properties of cubic (Pm3m) and orthorhombic (Pnma) CsPbX3 (X = I, Br, and Cl). We utilized the full potential linear augmented plane wave method, which is implemented in the WIEN2k code, to facilitate the investigation. Different exchange potentials were used to analyze the optoelectronic behavior using the available density functional theory methods. Our findings revealed that CsPbX3 perovskites display direct band gaps at the R and Г points for cubic (Pm3m) and orthorhombic (Pnma) structures, respectively. Among the exchange potentials, the mBJ-GGA method provided the most accurate results. These outcomes concurred with the experimental results. In both Pm3m and Pnma structures, interesting changes were observed when iodide (I) was replaced with bromine (Br) and then chlorine (Cl). The direct band gap at the R and Г points shifted to higher energy levels. Similarly, when I was replaced with Br and Cl, there was a noticeable decrease in the absorption coefficient, dielectric constants, refractive index, and reflectivity, in addition to a band gap shift to higher energy levels. [ABSTRACT FROM AUTHOR]

The classical light interactions of nanosilicon, which is a dielectric material, are exceedingly weak for radius r ≪ λ (wavelength), scaling as r6. It exhibits geometrical anisotropy-based depolarization, which is the basis for the very weak response in isotropic structures (nanosphere). Recently, surface enhanced Raman scattering (SERS) in DNA decorated with ultrasmall Si nanoparticles has been demonstrated, affording an effective alternative to plasmon–metal particles. In this paper, we execute fundamental quantum atomistic computation of 1 nm hydrogenated Si particles, with different surface reconstruction and termination, including Si–H, H–Si–Si–H (dimer molecules), or oxygenated dimer bridges (H–Si–O–Si–H). We obtain the mechanical vibrational modes of the particles. Our results show that by changing the surface configuration one can control the symmetry and normal vibration modes, and enhance the polarizability, polarity, and light interactions (scattering, absorption, and depolarization/memory). The low frequency polarizability (Raman scattering) shifts spatially from the interior to the surface, while the infrared polarity remains on the surface, but its bandwidth narrows spectrally. The results support previous infrared absorption and light scattering and depolarization measurements, as well recent SERS, which enable Si nanoparticles to be an effective alternative to plasmonic metal particles. Molecular surface reconstruction in terms of Si dimers and bridges were suggested as the source of the novel nonlinear and anisotropic luminescence and photonic properties of Si nanoparticles. Such control affords potential for optimizing the design and operation of a wide range of opto-electronic advanced scattering and luminescence devices. [ABSTRACT FROM AUTHOR]

Perovskite-type lead halides exhibit promising performances in optoelectronic applications, for which lasers are one of the most promising applications. Although the bulk structure has some advantages, perovskite has additional advantages at the nanoscale owing to its high crystallinity given by a lower trap density. Although the nanoscale can produce efficient light emission, its comparatively poor chemical and colloidal stability limits further development of devices based on this material. Nevertheless, bulk perovskites are promising as optical amplifiers. There has been some developmental progress in the study of optical response and amplified spontaneous emission (ASE) as a benchmark for perovskite bulk phase laser applications. Therefore, to achieve high photoluminescence quantum yields (PLQYs) and large optical gains, material development is essential. One of the aspects in which these goals can be achieved is the incorporation of a bulk structure of high-quality crystallization films based on inorganic perovskite, such as cesium lead halide (CsPb(Br/Cl)3), in polymethyl methacrylate (PMMA) polymer and encapsulation with the optimal thickness of the polymer to achieve complete surface coverage, prevent degradation, surface states, and surface defects, and suppress emission at depth. Sequential evaporation of the perovskite precursors using a single-source thermal evaporation technique (TET) effectively deposited two layers. The PL and ASEs of the bare and modified films with a thickness of 400 nm PMMA were demonstrated. The encapsulation layer maintained the quantum yield of the perovskite layer in the air for more than two years while providing added optical gain compared to the bare film. Under a picosecond pulse laser, the PL wavelength of single excitons and ASE wavelength associated with the stimulated decay of bi-excitons were achieved. The two ASE bands were highly correlated and competed with each other; they were classified as exciton and bi-exciton recombination, respectively. According to the ASE results, bi-exciton emission could be observed in an ultrastable CsPb(Br/Cl)3 film modified by PMMA with a very low excitation energy density of 110 µJ/cm2. Compared with the bare film, the ASE threshold was lowered by approximately 5%. A bi-exciton has a binding energy (26.78 meV) smaller than the binding energy of the exciton (70.20 meV). [ABSTRACT FROM AUTHOR]

The growth of nanocrystals (NCs) from metal oxide-based substrates with exposed high-energy facets is of particular importance for many important applications, such as solar cells as photoanodes due to the high reactivity of these facets. The hydrothermal method remains a current trend for the synthesis of metal oxide nanostructures in general and titanium dioxide (TiO2) in particular since the calcination of the resulting powder after the completion of the hydrothermal method no longer requires a high temperature. This work aims to use a rapid hydrothermal method to synthesize numerous TiO2-NCs, namely, TiO2 nanosheets (TiO2-NSs), TiO2 nanorods (TiO2-NRs), and nanoparticles (TiO2-NPs). In these ideas, a simple non-aqueous one-pot solvothermal method was employed to prepare TiO2-NSs using tetrabutyl titanate Ti(OBu)4 as a precursor and hydrofluoric acid (HF) as a morphology control agent. Ti(OBu)4 alone was subjected to alcoholysis in ethanol, yielding only pure nanoparticles (TiO2-NPs). Subsequently, in this work, the hazardous chemical HF was replaced by sodium fluoride (NaF) as a means of controlling morphology to produce TiO2-NRs. The latter method was required for the growth of high purity brookite TiO2 NRs structure, the most difficult TiO2 polymorph to synthesize. The fabricated components are then morphologically evaluated using equipment, such as transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), electron diffraction (SAED), and X-ray diffraction (XRD). In the results, the TEM image of the developed NCs shows the presence of TiO2-NSs with an average side length of about 20–30 nm and a thickness of 5–7 nm. In addition, the image TEM shows TiO2-NRs with diameters between 10 and 20 nm and lengths between 80 and 100 nm, together with crystals of smaller size. The phase of the crystals is good, confirmed by XRD. The anatase structure, typical of TiO2-NS and TiO2-NPs, and the high-purity brookite-TiO2-NRs structure, were evident in the produced nanocrystals, according to XRD. SAED patterns confirm that the synthesis of high quality single crystalline TiO2-NSs and TiO2-NRs with the exposed {001} facets are the exposed facets, which have the upper and lower dominant facets, high reactivity, high surface energy, and high surface area. TiO2-NSs and TiO2-NRs could be grown, corresponding to about 80% and 85% of the {001} outer surface area in the nanocrystal, respectively. [ABSTRACT FROM AUTHOR]

• The structural, elastic, electronic, magnetic, and optical properties of vacancy-ordered Rb 2 TcCl 6 have been thoroughly examined through the use of first-principles calculations. • The stability of Rb 2 TcCl 6 is demonstrated by the formation energy, optimization curves and phonon curves. • The spin-plarized electronic band structure and density of states (DOS) predict the semiconductor nature in both spin states. • The obtained magnetic moments for Rb 2 TcCl 6 reveal the potential of for spintronics. • An optical band gap with maximum absorption reveals that this compound is also useful for the application in optoelectronics. Due to their versatile properties, vacancy-ordered double perovskites offer a wide range of potential uses due to their versatile properties. We have thoroughly examined the physical characteristics of vacancy-ordered Rb 2 TcCl 6 in its cubic phase by employing the spin-polarized computations. The ground state energy and optimum structural parameters are obtained in order to assess the structural stability, which is further validated using the tolerance factor and formation energy values. The ductile character of Rb 2 TcCl 6 is revealed by a comprehensive evaluation of mechanical properties. Vickers hardness factor suggests that Rb 2 TcCl 6 can withstand against pressure-induced disturbance more strongly. A direct bandgap for spin-up is measured up to 2.33 eV, while for spin-dn it is 2.02 eV. According to the magnetic moments of 2.69 μ B , Rb 2 TcCl 6 is an attractive material for spintronic devices. A number of optical parameters are determined. For optoelectronic applications, Rb 2 TcCl 6 is an excellent choice due to its strong polarization in the visible and ultraviolet regions, as shown by its optical characteristics. [ABSTRACT FROM AUTHOR]

In this study, we present the effect of doping with antimony trisulfide (Sb 2 S 3) nanobare on the electrical, optical, structural, and morpholigcal properties of CH 3 NH 3 PbI 3 perovskite thin films. Doped with Sb 2 S 3 nanobare, the thin coatings demonstrated an exceptionally high degree of purity, featuring a tetragonal phase within its single-phase structure. This allowed for the creation of (110) textured CH 3 NH 3 PbI 3 films, which comprised micrometer-sized grains arranged in a vertical direction across the entire film thickness and featured high crystallinity. Additionally, the CH 3 NH 3 PbI 3 perovskites films exhibited significant optical absorption at appropriate energy levels and exhibited a high gachin rate of photons. Substance doping methods that can optimize the morphology of the perovskite active layer with large granules are exceedingly desirable in order to reduce charge carrier recombination. The synthesis of perovskite films with dimensions on the order of microns can be achieved by incorporating a regulated quantity of Sb 2 S 3 nanobare into the precursor solution. The incorporation of these textured CH 3 NH 3 PbI 3 :Sb 2 S 3 nanobare films significantly enhanced the power conversion efficiency (PCE) of the perovskite solar cells. The solar cell device configuration utilized in this investigation is as follows: glass/FTO/TiO 2 /CH 3 NH 3 PbI 3 :Sb 2 S 3 nanobars/spiro-OMeTAD/Au. By employing Sb 2 S 3 nanobars at a concentration of 9 mg/mL, we successfully attained an exceptional power conversion efficiency of 15.87 %. The resulting values for these parameters include an open-circuit voltage V OC of 1.09 V, a short-circuit current density J SC of 21.15 mA/cm2, and a fill factor FF of 68.87 %. • Sb 2 S 3 nanobars -doped CH 3 NH 3 PbI 3 perovskite-based solar cells are optimized for increased efficiency. • The effect of the Sb 2 S 3 nanobars on the structural, optical, and solar cell performance was studied. • Sb 2 S 3 nanobars affect carrier transport, surface roughness, crystallinity, and light absorption. • Optimal power conversion efficiency of 15.87 % was achieved. [ABSTRACT FROM AUTHOR]

Double perovskites based on rubidium have demonstrated potential for obtaining high solar cell power conversion efficiencies. Their distinct crystal structure and electrical characteristics influence these materials’ potential as effective light absorbers. In this present manuscript, a detailed scrutiny of the physical aspects of halide perovskites Rb2TlAsI6 and Rb2TlGaI6 is presented using density functional theory framework implanted in Wien2K code using. Modified Becke Johnson potential is employed to treat the exchange–correlation effects. A computed tolerance factor, octahedral tilting, and formation energy ensure the structural and thermodynamic stability of given structures. Three independent elastic constants and mechanical properties were computed using the Thomas Charpin method. Ductile nature of Rb2TlAsI6 and brittle nature for Rb2TlGaI6 is revealed from computed mechanical attributes. The Debye temperature for Rb2TlGaI6 (171.32 K) is noted higher than Rb2TlAsI6 (144.53 K). Electronic properties revealed a direct bandgap (1.09 eV) for Rb2TlAsI6 and an indirect bandgap (1.2 eV) for Rb2TlGaI6. Optical properties indicate high polarization and absorption of incident light, which is suitable for photovoltaic applications in the visible spectrum. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structural, elastic, electronic, transport, and optical properties of lead-free double perovskites K 2 CuBiX 6 (where X can be I, Br, or Cl) have been thoroughly examined through first-principles calculations. • The electronic band structure shows an increment in the energy gap after the replacement of Iodine with Bromine and Chlorine, which is also endorced by the density of states (DOS). An optical band gap with large absorption in the visible and UV region reveal the potential of K 2 CuBiX 6 (X = I, Br, Cl) for the applications in optoelectronics. • The perovskites exhibit substantial potential for renewable energy applications, as they demonstrate significant ZT values, which suggest their availability for thermoelectric devices. Potassium-based perovskites hold significant potential to revolutionize renewable technology by enabling more cost-effective and sustainable energy devices. The DFT incorporated in the Wein2K interface is used to provide an extensive investigation of the structural, mechanical, electrical, optical, and thermoelectric behavior of double perovskites K 2 CuBiX 6 (X = I, Br, Cl). Structural stability is confirmed through optimization curves, tolerance factor and octahedral tilting. Mechanical properties support the ductile character of K 2 CuBiX 6 (X = I, Br, Cl). Electronic band structures reveal that perovskite K 2 CuBiI 6 initially possesses a bandgap of 0.6 eV. This bandgap is increased to 0.97 eV when (I) atom is replaced with (Br) atom. Furthermore, a prominent shift in the bandgap value occurs when the bromine (Br) atom is replaced with a chlorine (Cl) atom, resulting in a bandgap of 1.3 eV. The Kramer-Kronig equations are used to evaluate the optical characteristic, which shows significant absorption in the visible range for all structures, allowing them to be utilized in optoelectronics. Numerous thermoelectric characteristics are calculated using the Boltzmann semi-classical theory. The perovskites exhibit substantial potential for renewable energy applications, as they demonstrate significant ZT values, along with elevated Seebeck coefficients and electrical conductivities, which enhance their suitability for utilization in clean energy technologies. [ABSTRACT FROM AUTHOR]

Composite materials with different concentration ratios of a hybrid of zero-dimensional (0-D) Cs4PbBr6 perovskite, which acts as a donor (D), and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), which acts as an acceptor (A), were successfully prepared via a solution blending method prior to being deposited onto glass substrates by a spin-coating technique. The influence of acceptor content on the structural, optical, and energy transfer properties of the donor was investigated. The perovskite nanocrystals formed thin films without any chemical interactions within a matrix of MEH-PPV in the blend. The possibility of dipole–dipole (non-radiative) energy transfer from the 0-D Cs4PbBr6 to the MEH-PPV was proven. The energy transfer parameters such as Ro (critical distance of the energy transfer), kapp (apparent quenching constant), ∅ D A (quantum yield of D in the presence of A), τ D A (lifetime of D in the presence of A), PDA (probability of energy transfer), η (efficiency of energy transfer), RDA (energy transfer radius), kET (energy transfer rate constant), TDR (total decay rate), Ao (critical concentration of A), and Aπ (conjugation length) were calculated based on the absorption and emission measurements. [ABSTRACT FROM AUTHOR]

Abstract In this paper, titanium dioxide (TiO 2) thin films, deposited on single crystal Si (111) substrates under different temperature conditions by Atomic Layer Deposition (ALD), have been systematically studied by X-ray diffraction, photoluminescence spectroscopy and spectroscopic ellipsometry methods. X-ray diffraction analysis showed that the prepared films have a polycrystalline brookite phase over a growth temperature range of (150–300 °C). Increasing the growth temperature resulted in systematic increase of texturing the polycrystalline grains along the (200) direction, with the film at 300 °C having the highest textur along the (200) direction. This was accompanied by improved photoluminescence of the TiO 2 films with the increasing the growth temperature. The improved crystallinity at higher temperatures was also reflected by higher refractive indices, which were deduced from spectroscopic ellipsometry measurements carried out on the grown films. Highlights • TiO 2 thin films with brookite phase successfully deposited on Si(111) using ALD. • Correlated Structural and optical properties perceived and studied. • Reduction of refractive index observed for films with ultra-small thicknesses. [ABSTRACT FROM AUTHOR]

The crystallization techniques of organic-inorganic hybrid perovskites (OIHP) are considered an effective method for light collector or light emitting applications. In this article, the optical band gap, electron-hole behavior, and energy band alignment are all key optoelectronic properties of crystalline perovskite structures studied in this study. For this reason, a perovskite solution was prepared in a single step and tetrahydrofuran (THF) was used as a solvent to dissolve both perovskite precursors. Rapid crystallization of perovskite in solution was observed, preventing the formation of homogenous perovskite thin films. Subsequently, the effect of THF solvent on the direct crystallization of MAPbI 3 perovskite without thermal annealing was investigated. Thermal annealing is considered necessary for perovskite crystal formation as it gives the molecules enough thermal energy to self-organize and form a well-ordered crystalline layer. The procedures that create perovskite crystals without thermal annealing give a novel method for room temperature film preparation (RT) and pave the way for the manufacture of low-cost, stable perovskite solar cells (PSCs). UV–vis absorption/reflectance, photoluminescence, XRD, and SEM were used to explore the effects of this approach on the optical and structural properties of MAPbI 3 perovskite thin films. • Crystallizing Growth of MAPbI 3 Perovskite Nanorod was demonstrated. • Perovskite precursor solution in THF is dried to form perovskite powder. • Fabrication of perovskite films without annealing. • Perovskite films were tested under ns laser. • The strong light emission allows the observation of ASE. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) based on TiO 2 nanoparticles and TiO 2 nanosheets with exposed {001} facets are investigated using laser-induced photovoltage and photocurrent transient decay (LIPVCD) measurements. We adopted a simplified version of LIPVCD technique, in which a single illumination light source and a laboratory oscilloscope could be conveniently used for the measurements. Although the {001} surface of TiO 2 nanosheets allowed a noticeably slower recombination with the electrolyte, this was counterpoised by a slower electron transport probably due to its planar morphology, resulting in a shorter diffusion length in TiO 2 nanosheets. The nanosheet morphology also resulted in less surface area and therefore reduced short circuit current density in the fabricated devices. Our work highlights the fact that the morphological parameters of TiO 2 nanosheets finally resulting after electrode film deposition is of no less importance than the reported efficient dye adsorption and slow electron recombination at the surface of individual nanosheets. [ABSTRACT FROM AUTHOR]

In this paper, we present a study of the structural and optical properties of organic–inorganic halide-based perovskite semiconductors with band gaps varying from NIR to visible at room temperature. Thin films of nanocrystalline CH 3 NH 3 PbI 3 with different concentrations of methylammonium iodide (MAI) have been successfully deposited onto glass substrates using single step spin-coating technique. The prepared films have been characterized by X-ray diffraction, optical absorption spectroscopy and photoluminescence measurements. X-ray diffraction scans revealed that even for stoichiometric atomic concentrations of MA:Pb:I of 1:1:3, the PbI 2 phase was also present. The PbI 2 phase showed a highly textured along the (001) direction in all the prepared films, with a crystallite size in the range of approximately 30–40 nm. The optical absorbance edge of CH 3 NH 3 PbI 3 thin films is described in terms of direct transition model proposed by Tauc in the strong absorption region. The band gap of the pure PbI 2 film was calculated to be 2.40 eV, whereas the band gap of the pervoskite film with stoichiometric ionic ratio of 1:1 PbI 2 and CH 3 NH 3 I was calculated to be 1.46 eV, while absorption coefficient is ~10 5 cm −1 . Photoluminescence measurements showed a red shift in the perovskite emission with increasing the MAI concentration, confirming the correct placement of the MA ions in the perovskite crystalline structure showing the PbI 2 octahedra. Our results confirm the existence of PbI 2 phase in the highly efficient perovskite solar cells, as demonstrated in the recent publication. [ABSTRACT FROM AUTHOR]

Photonic devices based on perovskite materials are considered promising alternatives for a wide range of these devices in the future because of their broad bandgaps and ability to contribute to light amplification. The current study investigates the possibility of improving the light amplification characteristics of CsPbBr3 perovskite quantum dot (PQD) films using the surface encapsulation technique. To further amplify emission within a perovskite layer, CsPbBr3 PQD films were sandwiched between two transparent layers of poly(methyl methacrylate) (PMMA) to create a highly flexible PMMA/PQD/PMMA waveguide film configuration. The prepared perovskite film, primed with a polymer layer coating, shows a marked improvement in both emission efficiency and amplified spontaneous emission (ASE)/laser threshold compared with bare perovskite films on glass substrates. Additionally, significantly improved photoluminescence (PL) and long decay lifetime were observed. Consequently, under pulse pumping in a picosecond duration, ASE with a reduction in ASE threshold of ~1.2 and 1.4 times the optical pumping threshold was observed for PQDs of films whose upper face was encapsulated and embedded within a cavity comprising two PMMA reflectors, respectively. Moreover, the exposure stability under laser pumping was greatly improved after adding the polymer coating to the top face of the perovskite film. Finally, this process improved the emission and PL in addition to enhancements in exposure stability. These results were ascribed in part to the passivation of defects in the perovskite top surface, accounting for the higher PL intensity, the slower PL relaxation, and for about 14 % of the ASE threshold decrease. [ABSTRACT FROM AUTHOR]

High-quality inorganic cesium lead halide perovskite CsPb(Br0.5Cl0.5)3 thin films were successfully achieved through evaporation of the precursors and deposition sequentially by a single-source thermal evaporation system. The different melting points of the precursors were enabled us to evaporate precursors one by one in one trip. The resulting films through its fabrication were smooth and pinhole-free. Furthermore, this technique enabled complete surface coverage by high-quality perovskite crystallization and more moisture stability oppositely of that produce by solution-processed. Then the perovskite films were encapsulated by evaporated a polymethyl methacrylate (PMMA) polymer as a specialized surface passivation approach with various thicknesses. The blue emission, high photoluminescence quantum yield (PLQY), stable, and low threshold of amplified spontaneous emission (ASE) properties of CsPb(Br0.5Cl0.5)3 films in the bulk structure at room temperature were achieved. The effects of the surface-passivation layer and its thickness on the optical response were examined. Detailed analysis of the dependence of ASE properties on the surface passivation layer thickness was performed, and it was determined this achieves performance optimization. The ASE characteristics of bare perovskite thin film were influenced by the incorporation of the PMMA with various thicknesses. The improvement to the surface layer of perovskite thin films compared to that of the bare perovskite thin film was attributed to the combination of thermal evaporation deposition and surface encapsulation. The best results were achieved when using a low PMMA thickness up to 100 nm and reducing the ASE threshold by ~11 μJ/cm2 when compared with free-encapsulation and by ~13 μJ/cm2 when encapsulation occurs at 200 nm or thicker. Compared to the bare CsPb(Br0.5Cl0.5)3, ASE reduced 1.1 times when the PMMA thickness was 100 nm. [ABSTRACT FROM AUTHOR]

Organic–inorganic halide organometal perovskites have demonstrated very promising performance in optoelectronic applications, but their relatively poor chemical and colloidal stability hampers the further improvement of devices based on these materials. Perovskite material engineering is crucial for achieving high photoluminescence quantum yields (PLQYs) and long stability. Herein, these goals are attained by incorporating bulk-structure CsPbBr3, which prevents colloidal degradation, into polymethyl methacrylate (PMMA) polymer in thin-disk form. This technology can potentially realize future disk lasers with no optical and structural contributions from the polymer. The polycrystalline CsPbBr3 perovskite particles were simply obtained by using a mechanical processing technique. The CsPbBr3 was then incorporated into the PMMA polymer using a solution blending method. The polymer enhanced the PLQYs by removing the surface trap states and increasing the water resistance and stability under ambient conditions. In our experimental investigation, the CsPbBr3/PMMA composites were extraordinarily stable and remained strongly luminescent after water immersion for three months and air exposure for over one year, maintaining 80% of their initial photoluminescence intensity. The CsPbBr3/PMMA thin disk produced amplified spontaneous emission for a long time in air and for more than two weeks in water. [ABSTRACT FROM AUTHOR]

The effect of halide composition on the structural, electronic, and optical properties of CsPb(Br1−xClx)3 perovskite was investigated in this study. When the chloride (Cl) content of x was increased, the unit cell volume decreased with a linear function. Theoretical X-ray diffraction analyses showed that the peak (at 2θ = 30.4°) shifts to a larger angle (at 2θ = 31.9°) when the average fraction of the incorporated Cl increased. The energy bandgap (Eg) was observed to increase with the increase in Cl concentration. For x = 0.00, 0.25, 0.33, 0.50, 0.66, 0.75, and 1.00, the Eg values calculated using the Perdew–Burke–Ernzerhof potential were between 1.53 and 1.93 eV, while those calculated using the modified Becke−Johnson generalized gradient approximation (mBJ–GGA) potential were between 2.23 and 2.90 eV. The Eg calculated using the mBJ–GGA method best matched the experimental values reported. The effective masses decreased with a concentration increase of Cl to 0.33 and then increased with a further increase in the concentration of Cl. Calculated photoabsorption coefficients show a blue shift of absorption at higher Cl content. The calculations indicate that CsPb(Br1−xClx)3 perovskite could be used in optical and optoelectronic devices by partly replacing bromide with chloride. [ABSTRACT FROM AUTHOR]

The triplet energy transfer mechanism of novel poly(9,9-di-n-octylflourenyl-2,7-diyl) (PFO)/poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/CsPbBr3 perovskite quantum dot (PQD) hybrid thin films was comprehensively investigated. The concentrations of PFO and MEH-PPV in all the specimens were fixed, while the PQD content was varied with various weight ratios and premixed by a solution blending method before it was spin-coated onto glass substrates. The triplet non-radiative Förster resonance energy transfers (FRETs) in the PFO/MEH-PPV/PQDs ternary blend, the dual FRET from PFO to both PQDs and MEH-PPV, and the secondary FRET from PQDs to MEH-PPV were observed. The values of the Förster radius (Ro) of FRET from PFO to MEH-PPV in the presence of various PQD contents (Case I) increased from 92.3 to 104.7 Å, and they decreased gradually from 68.0 to 39.5 Å for FRET from PFO to PQDs in the presence of MEH-PPV (Case II). These Ro values in both cases confirmed the dominance of FRET in ternary hybrid thin films. Upon increasing the PQD content, the distance between the donor and acceptor molecules (RDA) and the conjugation length (Aπ) in both cases gradually decreased. The small values of Ro, RDA, and Aπ with a decrease in the energy transfer lifetime (τET) due to an increase in the PQD contents in both Cases I and II confirmed the efficient FRET in the hybrid. To prevent intermolecular transfer in PFO, the concentrations of MEH-PPV (Case I) and PQDs (Case II) should be decreased to a range of 0.57–0.39 mM and increased in the range of 1.42–7.25 mM. [ABSTRACT FROM AUTHOR]

Amplified spontaneous emission (ASE) threshold in CsPbBr 3 quantum dot films is systematically reduced by introducing high quality TiO 2 compact layer grown by atomic-layer deposition. Uniform and pinhole-free TiO 2 films of thickness 10, 20 and 50 nm are used as a substrates for CsPbBr 3 quantum dot films to enhance amplified spontaneous emission performance. The reduction is attributed indirectly to the improved morphology of TiO 2 compact layer and subsequently CsPbBr 3 active layer as grown on better quality substrates. This is quantified by the reduced roughness of the obtained films to less than 5 nm with 50 nm TiO 2 substrate. Considering the used growth method for the quantum dot film, the improved substrate morphology maintains better the structure of the used quantum dots in the precursor solution. This results in better absorption and hence lower threshold of ASE. Besides that, the improved film quality results further in reducing light scattering and hence additional slight optical enhancement. The work demonstrates a potential venue to reduce the amplified spontaneous emission threshold of quantum dot films and therefore enhanced their optical performance. [ABSTRACT FROM AUTHOR]

In this study, methyl ammonium lead Iodide perovskite (CH 3 NH 3 PbI 3 ≡MAPbI 3) was deposited as a thin planar film on a glass substrate at room temperature using one-step and two-step methods. The effect of each method of preparation on the structural, morphological, and optical properties was investigated. The results show that the average size of the MAPbI 3 crystallites are ~57.3 nm and 25.8 nm for the one and two-step methods, respectively. The pore-filling of the perovskite film is incomplete when using the one-step process but completely filled when two-step method was used. Therefore, both one-step and two-step methods lead to perovskite islands and void-free perovskite layers, respectively. Scanning emission microscopy images show that the quality of the film produced by two-step is much better than that formed via one-step. Moreover, the perovskite film prepared via one-step method tends to produce a higher pinhole density than two-step, and thus lower coverage that leads to a low absorption and a low absorption coefficient. Parameters such as optical absorption coefficient, refractive index, extinction coefficient, dielectric constant, and optical conductivity were also estimated. The intensities of both photoluminescence and amplified spontaneous emission spectra of MAPbI 3 sample prepared via one-step method were found to be lower than those prepared via two-step. • High quality MAPbI 3 perovskite films were prepared by one and two step methods. • The preparation method has significant effect on the optical properties. • Two-step spin-coating method results in a better morphology and interface. • Two-step prepared films exhibited better absorbance. • Thus, the two-step method is more promising for photovoltaic devices. [ABSTRACT FROM AUTHOR]

The structural, electronic, and optical features of CsPb(I 1-x Br x) 3 (x = 0, 0.25, 0.50, 0.75, and 1.0) compounds were evaluated using first-principles calculations based on the full-potential linear augmented plane wave (FP-LAPW). The ground-state properties were examined, with a focus on the structural, electronic, and optical properties of the compounds. The structural features were computed using the PBE-GGA potential, revealing that both the lattice constant and bulk modulus varied nonlinearly with respect to the bromide concentration. Theoretical X-ray diffraction analyses revealed peak shifts to larger angles when the average fraction of bromide incorporated increased, indicating shrinkage in the lattice. While the E g values were calculated using the PBE-GGA potential and resulted the 1.45, 1.43, 1.53, 1.50, and 1.77 eV values, the mBJ-GGA potential values resulted the 1.90, 1.81, 2.11, 2.12, and 2.50 eV for CsPbI 3 , CsPbI 2.75 Br 0.25 , CsPbI 1.5 Br 1.5 , CsPbI 0.25 Br 2.75 , and CsPbBr 3 respectively. In addition to that, the E g values of CsPbI 1.5 Br 1.5 which were calculated using other potentials: LDA and PBEsol potentials have resulted the 1.43 and 1.49 eV values, respectively. The E g of CsPb(I 1-x Br x) 3 obtained using mBJ-GGA potential has relatively matched with previously reported experimental values. The calculated effective masses are highly correlated with the energies of E g, the valence-band maximum (VBM), and conduction-band minimum (CBM). We observed that there was an increase, with small bowing parameters (b), in E g value as the Br concentration increases in the CsPb(I 1-x Br x) 3 compounds. The semiconductor characteristic was prominent in the observed band profiles when PBE-GGA and mBJ-GGA potentials were applied. Additionally, the optical properties were examined in details. The calculations indicate that the CsPb(I 1-x Br x) 3 compounds are promising candidates for optoelectronics. Image 1 • The structural, electrical and optical properties of CsPb(I 1-x Br x) 3 were investigated using the PBE-GGA and mBJ-GGA. • An increase in the band gap energy (Eg) values of 0.32 eV (PBE-GGA) and 0.60 eV (mBJ-GGA) when substituting I with Br. • The calculated band gap (Eg) values using the mBJ-GGA were better matched with the experimental values. • The effective masses of electron and hole were calculated using PBE-GGA and mBJ-GGA potentials. • All the optical properties of CsPb(I1-xBrx)3 were investigated using PBE-GGA and mBJ-GGA potentials in details. [ABSTRACT FROM AUTHOR]