Uniaxial-Oriented Chiral Perovskite for Flexible Full-Stokes Polarimeter.

Full-Stokes polarization detection, with high integration and portability, offers an efficient path toward next-gen multi-information optoelectronic systems. Nevertheless, current techniques relying on optical filters create rigid and bulky configurations, limiting practicality. Here, a flexible, filter-less full-Stokes polarimeter featuring a uniaxial-oriented chiral perovskite film is first reported. It is found that, the strategic manipulation of the surfactant-mediated Marangoni effect during blade coating, is crucial for guiding an equilibrious mass transport to achieve oriented crystallization. Through this approach, the obtained uniaxial-oriented chiral perovskite films inherently possess anisotropy and chirality, and thereby with desired sensitivity to both linearly polarized light and circularly polarized light vectors. The uniaxial-oriented crystalline structure also improves photodetection, achieving a specific detectivity of 5.23 × 1013 Jones, surpassing non-oriented devices by 10×. The as-fabricated flexible polarimeters enable accurate capture of full-Stokes polarization without optical filters, exhibiting slight detection errors for the Stokes parameters: ΔS1 = 9.2%, ΔS2 = 8.6%, and ΔS3 = 6.5%, approaching the detection accuracy of optics-filter polarimeters. This proof of concept also demonstrates applications in matrix polarization imaging.

Fluoride Removal Using Nanofiltration-Ranged Polyamide Thin-Film Nanocomposite Membrane Incorporated Titanium Oxide Nanosheets.

Drinking water defluoridation has attracted significant attention in the scientific community, from which membrane technology, by exploring thin film nanocomposite (TFN) membranes, has demonstrated a great potential for treating fluoride-contaminated water. This study investigates the development of a TFN membrane by integrating titanium oxide nanosheets (TiO2 NSs) into the polyamide (PA) layer using interfacial polymerization. The characterization results suggest that successfully incorporating TiO2 NSs into the PA layer of the TFN membrane led to a surface with a high negative charge, hydrophilic properties, and a smooth surface at the nanoscale. The TFN membrane, containing 80 ppm of TiO2 NSs, demonstrated a notably high fluoride rejection rate of 98%. The Donnan-steric-pore-model-dielectric-exclusion model was employed to analyze the effect of embedding TiO2 NSs into the PA layer of TFN on membrane properties, including charge density (Xd), the pore radius (rp), and pore dielectric constant (εp). The results indicated that embedding TiO2 NSs increased Xd and decreased the εp by less than the TFC membrane without significantly affecting the rp. The resulting TFN membrane demonstrates promising potential for application in water treatment systems, providing an effective and sustainable solution for fluoride remediation in drinking water.

A DFT approach to correlate the physical characteristics of novel chalcopyrites ASbN2(A = Li, Na) for green technology.

Semiconductor chalcopyrite compounds have been a subject of research interest due to their diverse range of physical properties that have captured the attention of scientists. In this ongoing research, we have examined the physical characteristics of LiSbN2 and NaSbN2 chalcopyrites using DFT. The modified Becke-Johnson (mBJ) potential is utilized for the computation of electronic structures. The stability is attained with negative formation energies and optimization curves. A bandgap of 2.60 eV in LiSbN2 and 3.15 eV in NaSbN2 has been achieved, which is further endorsed by the density of states. An in-depth analysis of the optical properties unveils the potential utility of LiSbN2 and NaSbN2 in various photovoltaic devices, attributed to its pronounced absorption in the UV spectrum. The transport characteristics are also assessed through various transport characteristics. The large electrical conductivity and ZT values for both chalcopyrite compounds are attained. Due to their remarkable capability to convert heat into electricity, these materials display potential for use in thermoelectric devices.

Synthesis, thermoluminescence characterizations, and photon attenuation parameters of MgAl2 O4 structure doped with different ions.

In this work, different ion co-doped Mg1-x Al2 O4 nanophosphors, coded as M5Cr-5La A, M5Cr-5Cu A, M0.07Si-0.03Ce A, and M0.05Ti-0.05La A, where 5Cr-5La, 5Cr-5Cu, 0.07Si-0.03Ce, and 0.05Ti-0.05La representing the added ions (mol%), were prepared using the sol-gel method. Phase structure, transmission electron microscope (TEM) images, and element feasibility were checked using X-ray diffraction, TEM analysis, and energy dispersive X-ray (EDX) spectroscopy. Their thermoluminescence (TL) response was checked using a 5 Gy γ-test dose. The M0.05Ti-0.05La A sample was found to be best for the TL response with an ~1.1 times response compared with that of the MTS-700 commercial detector. A wide range of dose-responses for the M0.05Ti-0.05La A sample was found up to a 20 Gy γ-dose with the lowest detectable dose of ⁓23 µGy. Photon attenuation parameter results were Zeff ⁓10, which mean that the M0.05Ti-0.05La A sample could be considered as a near tissue equivalent material. Due to this study, the M0.05Ti-0.05La A sample can be considered as a promising detector for application in personal and medical dosimetric monitoring.

Broadband Near-Infrared Emission from 0D Hybrid Copper Halides.

Metal halides have attracted increasing attention owing to their outstanding optoelectronic properties and tunable emission characteristics. Among these, low-dimensional metal halides have emerged as a novel and efficient luminescent material, primarily attributed to their broad spectral emission induced by self-trapped excitons (STEs). However, achieving highly efficient deep red and near-infrared (NIR) emission in metal halides remains a challenge. In this study, we report a novel zero-dimensional (0D) copper-based metal halide [Na2(DMSO)8]Cu4Br6 as the NIR light source, which exhibits a full width at half-maximum (FWHM) of 195 nm peaking at 685 nm, an impressive quantum efficiency of 68% and a large Stokes shift of 299 nm. Through comprehensive spectral analysis and meticulous data calculations, we substantiate that the emission originates from STEs formed within the 0D structure. Furthermore, we demonstrate the potential application of [Na2(DMSO)8]Cu4Br6 as an invisible light source in night vision by combining it with a commercially available 365 nm ultraviolet (UV) chip. This work not only enriches the family of low-dimensional metal halide materials but also inspires the potential of low-dimensional metal halides in night vision applications.

Multidentate Chelation Achieves Bilateral Passivation toward Efficient and Stable Perovskite Solar Cells with Minimized Energy Losses.

Defects in the electron transport layer (ETL), perovskite, and buried interface will result in considerable nonradiative recombination. Here, a bottom-up bilateral modification strategy is proposed by incorporating arsenazo III (AA), a chromogenic agent for metal ions, to regulate SnO2 nanoparticles. AA can complex with uncoordinated Sn4+/Pb2+ in the form of multidentate chelation. Furthermore, by forming a hydrogen bond with formamidinium (FA), AA can suppress FA+ defects and regulate crystallization. Multiple chemical bonds between AA and functional layers are established, synergistically preventing the agglomeration of SnO2 nanoparticles, enhancing carrier transport dynamics, passivating bilateral defects, releasing tensile stress, and promoting the crystallization of perovskite. Ultimately, the AA-optimized power conversion efficiency (PCE) of the methylammonium-free (MA-free) devices (Rb0.02(FA0.95Cs0.05)0.98PbI2.91Br0.03Cl0.06) is boosted from 20.88% to 23.17% with a high open-circuit voltage (VOC) exceeding 1.18 V and ultralow energy losses down to 0.37 eV. In addition, the optimized devices also exhibit superior stability.

Water-Molecule-Induced Reversible Fluorescence in a One-Dimensional Mn-Based Hybrid Halide for Anticounterfeiting and Digital Encryption-Decryption.

Hybrid metal halides with reversible transformation of structure and luminescence properties have attracted significant attention in anticounterfeiting. However, their long transition time and slow response rate may hinder the rapid identification of confidential information. Here, a one-dimensional hybrid manganese-based halide, i.e., (C5H11N3)MnCl2Br2·H2O, is prepared and demonstrates the phenomenon of water-molecule-induced reversible photoluminescence transformation. Heating for <40 s induces a dynamic transfer of red-emissive (C5H11N3)MnCl2Br2·H2O to green-emissive (C5H11N3)MnCl2Br2. In addition, the green emission can gradually revert to red emission during a cooling process in a moist environment, demonstrating excellent reversibility. It is found that the water molecule acts as an external stimulus to realize the reversible transition between red and green emission, which also exhibits remarkable stability during repeated cycles. Furthermore, with the assistance of heating and cooling, a complex digital encryption-decryption and an optical "AND" logical gate are achieved, facilitating the development of anticounterfeiting information security.

Electronic Structure and Optical Properties of Inorganic Pm3m and Pnma CsPbX3 (X = Cl, Br, I) Perovskite: A Theoretical Understanding from Density Functional Theory Calculations.

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.

Additive Conformational Engineering To Improve the PbI2 Framework for Efficient and Stable Perovskite Solar Cells.

The PbI2 framework is critical for two-step fabricated perovskite solar cells. This study investigates the effects of introducing two functional urea-based molecules, biuret (BU) and dithiobiuret (DTBU), into the PbI2 precursor solution on the absorber layer and overall device performance. BU, which contains C═O, enhanced device performance and stability, whereas DTBU, which contains C═S, had negative effects. Research analysis revealed the differences in the spatial structures of the two urea-based molecules. The introduction of symmetrical BU molecules facilitated the crystallization of PbI2, whereas the introduction of DTBU with a twisted molecular structure led to inferior crystallization performance of PbI2. The perovskite thin film, obtained by introducing BU into the PbI2 precursor solution, demonstrated superior performance, characterized by a decreased defect density and an extended carrier lifetime. The device performance and stability were enhanced, resulting in higher open-circuit voltage and fill factor. The highest achieved power conversion efficiency was 23.50%. After 1300 h of storage under unpackaged conditions at 30-40% humidity, the devices maintained 93% of their initial efficiency. Conversely, the devices prepared with DTBU doping exhibited inferior performance and stability, displaying power conversion efficiency below 10% and faster degradation under the same humidity conditions.

Surface Passivation for Promotes Bi-Excitonic Amplified Spontaneous Emission in CsPb(Br/Cl)3 Perovskite at Room Temperature.

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).

Successful Growth of TiO2 Nanocrystals with {001} Facets for Solar Cells.

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.

Conjugated Polymers-Based Ternary Hybrid toward Unique Photophysical Properties.

The improvement of optical and optoelectronic properties of the individual poly [2-methoxy-5- (2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene]-End capped with Dimethyl phenyl (OC1C10-PPV-DMP), and poly (9,9'-di- n -octylfluorenyl-2,7-diyl) (F8) was revealed by blending them in ternary hybrid with optimal ratio (F8/2 wt.% MEH-PPV/2 wt.% OC1C10-PPV-DMP). All individual and optimal ternary solutions were prepared via the solution-blending method followed by depositing them onto glass and ITO substrates using spin-coating technique. The semi-crystalline phase of the ternary hybrid and the strong mixing between the conjugated polymers were evidenced by observing the X-ray diffraction patterns that related to F8 into the hybrid diffractogram. The optical and optoelectronic properties of all prepared thin films were investigated in terms of absorption and emission spectra, Commission International d'Eclairage (CIE) coordinates, and current-voltage (I-V) characterizations. Emission peaks at the entire range of visible spectrum can be revealed from the ternary hybrid of the three individual conjugated polymers, producing white emission as evidenced from the emission spectrum and CIE coordinates of the hybrid. Among all fabricated organic light-emitting diodes (OLEDs) devices, the ternary hybrid-based-OLED revealed the best performance in terms of current and turn-on voltage.

Amplified Spontaneous Emission from Thermally Evaporated High-Quality Thin Films of CsPb(Br1-xYx)3 (Y = I, Cl) Perovskites.

As a wavelength-tunable lasing material, perovskites are now generating a lot of scientific attention. Conventional solution-processed CsPbX3 perovskite films sometimes suffer unavoidable pinhole defects and poor surface morphology, severely limiting their performance on amplified spontaneous emission (ASE) and lasing application. Herein, a thermal evaporation approach is explored in our work to achieve a uniform and high-coverage CsPb(Br1-xYx)3 (Y = I, Cl) perovskites polycrystalline thin film. The ASE of these films was studied using a picosecond laser system. The ASE profile increases rapidly over the narrow peak in relation to the laser pump intensity, confirming the development of stimulated emission. ASE began when the energy density threshold was reached and ranged between 25 and 170 µJ/cm2 per pulse for perovskite materials when replacing I with Br and then Cl. This work emphasizes the notable optical properties of high-quality perovskite thin films, leading to possible accessible uses in optoelectronic applications.

Density Functional Theory Analysis of Structural, Electronic, and Optical Properties of Mixed-Halide Orthorhombic Inorganic Perovskites.

Inorganic metal-halide perovskites hold a lot of promise for solar cells, light-emitting diodes, and lasers. A thorough investigation of their optoelectronic properties is ongoing. In this study, the accurate modified Becke Johnson generalized gradient approximation (mBJ-GGA) method without/with spin orbital coupling (SOC) implemented in the WIEN2k code was used to investigate the effect of mixed I/Br and Br/Cl on the electronic and optical properties of orthorhombic CsPb(I1-x Br x )3 and CsPb(Br1-x Cl x )3 perovskites, while the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) method was used to investigate their structural properties. The calculated band gap (E g) using the mBJ-GGA method was in good agreement with the experimental values reported, and it increased clearly from 1.983 eV for CsPbI3 to 2.420 and 3.325 eV for CsPbBr3 and CsPbCl3, respectively. The corrected mBJ + SOC E g value is 1.850 eV for CsPbI3, which increased to 2.480 and 3.130 eV for CsPbBr3 and CsPbCl3, respectively. The calculated photoabsorption coefficients show a blue shift in absorption, indicating that these perovskites are suitable for optical and optoelectronic devices.

Controlling the Emission Spectrum of Binary Emitting Polymer Hybrids by a Systematic Doping Strategy via Förster Resonance Energy Transfer for White Emission.

Tuning the emission spectrum of both binary hybrids of poly (9,9'-di-n-octylfluorenyl-2,7-diyl) (PFO) with each poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene] end-capped with Dimethyl phenyl (MDMO-PPV-DMP) by a systematic doping strategy was achieved. Both binary hybrid thin films of PFO/MEH-PPV and PFO/MDMO-PPV-DMP with various weight ratios were prepared via solution blending method prior to spin coating onto the glass substrates. The conjugation length of the PFO was tuned upon addition of acceptors (MEH-PPV or MDMO-PPV-DMP), as proved from shifting the emission and absorption peaks of the binary hybrids toward the acceptor in addition to enhancing the acceptor emission and reducing the absorbance of the PFO. Förster resonance energy transfer (FRET) is more efficient in the binary hybrid of PFO/MDMO-PPV-DMP than in the PFO/MEH-PPV. The efficient FRET in both hybrid thin films played the major role for controlling their emission and producing white emission from optimum ratio of both binary hybrids. Moreover, the tuning of the emission color can be attributed to the cascade of energy transfer from PFO to MEH-PPV, and then to MDMO-PPV-DMP.

Enhancement of Light Amplification of CsPbBr3 Perovskite Quantum Dot Films via Surface Encapsulation by PMMA Polymer.

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.

Achieving Optical Gain of the CsPbBr3 Perovskite Quantum Dots and Influence of the Variable Stripe Length Method.

High-quality inorganic cesium lead halide perovskite quantum dot (CsPbBr3 PQD) thin films were successfully deposited directly from a powdered source and used as an active laser medium following the examination of their distinctive surface and structural properties. To determine the suitability of the CsPbBr3 PQDs as an active laser medium, amplified spontaneous emission (ASE) and optical gain properties were investigated under picosecond pulse excitation using the variable stripe length (VSL) method. The thin film of CsPbBr3 PQDs has exhibited a sufficient value of the optical absorption coefficient of ∼0.86 × 105 cm-1 near the band edge and a direct band gap energy E g ∼2.38 eV. The samples showed enhanced emission, and ASE was successfully recorded at a low threshold. The light emitted from the edge was observed near 2.40 and 2.33 eV for the stimulated emission (SE) and ASE regimes, respectively. The nonradiative decay contributes excitons dominant over biexcitons in the sample edge emission above the ASE threshold, making it practical for CsPbBr3 PQDs to be used as optical gain media without undergoing repeated SE processes above the threshold over long periods. A high value of the optical gain coefficient was recorded at 346 cm-1.

Tuning Photophysical Properties of Donor/Acceptor Hybrid Thin- Film via Addition of SiO2/TiO2 Nanocomposites.

The influence of SiO2/TiO2 nanocomposites (STNCs) content on non-radiative energy transfer (Förster-type) from poly (9,9'-dioctylfluorene-2,7-diyl) (PFO) to poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) using steady-state and time-resolved photoluminescence spectroscopies was investigated at room temperature. The improved energy transfer from PFO to MEH-PPV upon an increment of the STNCs was achieved by examining absorbance, emission (PL) and photoluminescence excitation (PLE) spectra. The shorter values of the quantum yield (φDA) and lifetime (τDA) of the PFO in the hybrid thin films compared with the pure PFO, indicating efficient energy transfer from PFO to MEH-PPV with the increment of STNCs in the hybrid. The energy transfer parameters can be tuned by increment of the STNCs in the hybrid of PFO/MEH-PPV. The Stern-Volmer value (kSV), quenching rate value (kq), Förster radius (R0), distance between the molecules of PFO and MEH-PPV (RDA), energy transfer lifetime (τET), energy transfer rate (kET), total decay rate of the donor (TDR), critical concentration (Ao), and conjugation length (Aπ) were calculated. The gradually increasing donor lifetime and decreasing acceptor lifetime, upon increasing the STNCs content, prove the increase in conjugation length and meanwhile enhance in the energy transfer.

Single-Source Thermal Evaporation Growth and the Tuning Surface Passivation Layer Thickness Effect in Enhanced Amplified Spontaneous Emission Properties of CsPb(Br0.5Cl0.5)3 Perovskite Films.

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.

Ultra-Stable Polycrystalline CsPbBr3 Perovskite-Polymer Composite Thin Disk for Light-Emitting Applications.

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.