Photoluminescence PL Research Articles

Effect of film thickness on photoelectric properties of <inline-formula><tex-math id="Z-20220216211654">\begin{document}${\boldsymbol{\beta}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20211744_Z-20220216211654.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20211744_Z-20220216211654.png"/></alternatives></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> films prepared by radio frequency magnetron sputtering

In this work, β-Ga<sub>2</sub>O<sub>3</sub> films with different thickness are prepared on (001) sapphire substrates at room temperature by the radio frequency magnetron sputtering technology, then the samples are annealed in an Ar atmosphere at 800 ℃ for 1h. The effects of film thickness on the phase composition, surface morphology, optical property, and photoelectric detection performance are investigated using XRD, SEM, UV-Vis spectrophotometer, PL photoluminescence spectrometer, and Keithley 4200-SCS semiconductor characterization system. The results show that as the film thickness increases, the film crystallinity is improved, films with a thickness of 840 nm exhibit best quality, while those with a thickness of 1050 nm declines a little in quality. The β-Ga<sub>2</sub>O<sub>3</sub> films with different thickness exhibit obvious ultraviolet light absorption in the solar-blind region with wavelengths of 200–300 nm, and the bandgap width increases with the film thickness increasing. All the β-Ga<sub>2</sub>O<sub>3</sub> films show a broad UV-green light emission peaks in a wavelength range of 350–600 nm. As the film thickness increases, the intensities of the emission peaks of ultraviolet, violet, and blue light are greatly reduced, indicating that oxygen vacancy-related defects (<i>V</i><sub>O</sub>, <i>V</i><sub>Ga</sub>–<i>V</i><sub>O</sub>) are greatly suppressed with film thickness increasing. Solar-blind ultraviolet photodetector is fabricated based on the β-Ga<sub>2</sub>O<sub>3</sub> film. Its photoelectric detection performances (the photo-to-dark current ratio, responsivity, detectivity, and external quantum efficiency) also increase first and decrease then with the increase of film thickness. The β-Ga<sub>2</sub>O<sub>3</sub> ultraviolet photodetector prepared by a thin film with a thickness of 840 nm exhibits a very low dark current (4.9 × 10<sup>–12</sup> A) under a 5 V bias voltage and an ultraviolet light with a wavelength of 254 nm (600 μW/cm<sup>2</sup>). It exhibits a high photo-to-dark current ratio of 3.2 × 10<sup>5</sup>, and a short response time of 0.09/0.80 s (rising time) and 0.06/0.53 s ratio (falling time). Its responsivity (<i>R</i>), detectivity (<i><u>D</u></i><sup> *</sup>), and the external quantum efficiency (EQE) are 1.19 mA/W, 1.9 × 10<sup>11</sup> Jones, and 0.58%, respectively. The prepared device has quantifiable characteristics, and its photocurrent increases almost linearly with the increase of applied voltage and optical power density, and therefore can work in a linear dynamic region, which indicates that it is very suitable for fabricating the solar-blind ultra-violet detectors.

Er3+ Incorporated Transparent Ternary Nanocomposite as Active Core Material in Polymer Optical Preform with Improved Photo-emission Performance

Background: A polymer as a host in the optical waveguide has many advantages and, when doped with rare-earth (RE) elements, offers an efficient connection, compared to its glassbased counterparts as an amplifier. However, a polymer matrix causes the concentration quenching effect of REs in the polymer matrix, making the fabrication of RE-doped polymer waveguides more complicated as compared to the fabrication of glass-based complements. Moreover, controlling scattering loss at the particle-polymer interface for maintaining the optical clarity of the composite is also a great challenge. Objective: The main aim of the present study was to optimize the synthesis of Er2O3 grafted Polymethylmethacrylate (PMMA)-Polystyrene (PS) composite based transparent ternary nanocomposite and its characterization to implement them as a potential material for active core in Polymer Optical Preform (POP). Methods: Nano Erbium Oxide (Er2O3) was successfully synthesized by the wet-chemical method and encapsulated by a polymerizable surfactant, i.e., 3-Methacyloxypropyltrimethoxy silane (MPS). The encapsulated nanoparticles were further subjected to grafting with PMMA using in-situ polymerization of methyl methacrylate (MMA) followed by blending with PS via solvent mixing technique. Results: The optical transparency of the ternary composite was achieved by fine-tuning the diameter (15-20 nm) of the PMMA coated Er2O3 . The crystallinity present in Er2O3 was significantly reduced after PMMA coating. The comparatively higher refractive index obtained at 589 nm wavelength for the synthesized material indicated its usability as active core material in the presence of a commercial acrylate cladding tube. A photoluminescence (Pl) study indicated that the technique might be used for a higher level of Er3+ doping in polymer matrix without sacrificing its transparency. Conclusion: The obtained results indicated that the sample synthesized with the adopted technique gives better Pl intensity compared to the other methods of Er3+ incorporation in polymer optical preform (POP).

Exciton versus free carrier emission: Implications for photoluminescence efficiency and amplified spontaneous emission thresholds in quasi-2D and 3D perovskites

Among perovskite semiconductors, quasi-two-dimensional (2D) materials are attractive for the pursuit of electrically driven lasing given their excellent performance in light-emitting diodes (LEDs) and their recent success in continuous-wave optically pumped lasing. We investigate the spontaneous photoluminescence emission and amplified spontaneous emission (ASE) of a series of quasi-2D emitters, and their directly analogous 3D materials formed by removing the 2D organic spacer by annealing. Although the PL photoluminescence (PL) (at low optical excitation power) from quasi-2D films with high 2D spacer fractions can be much brighter than that from their 3D counterparts, the ASE thresholds of these quasi-2D materials tend to be higher. This counter-intuitive behavior is investigated through time-resolved photophysical studies, which reveal the emission in the high-spacer-content quasi-2D perovskite can be exclusively excitonic, and the exciton–exciton annihilation of quasi-2D perovskite starts to take over the exciton dynamics at a low exciton density (<1016 cm−3). To lower ASE thresholds in quasi-2D materials it is necessary to increase the volume fraction of thick quantum wells, which we achieve by decreasing the spacer content or by utilizing 1-naphthylmethylamine (NMA) linkers. The increase of the volume fraction of thick quantum wells correlates with an increased contribution of free carrier recombination to the emission process of the quasi-2D materials. These results suggest that material development of quasi-2D materials for gain applications should target fast free charge carrier recombination rates by engineering the well thickness and size and not maximum photoluminescence quantum yields under low power excitation.

Synthesis & thermoluminescence characteristics & structural and optical studies of ZnO/Ag/ZnO system for dosimetric applications

This study demonstrated a novel dosimeter ZnO/Ag/ZnO) multilayer thin films that were fabricated via radiofrequency and direct current RF/DC sputtering at room temperature. The sequence of ZnO (200 nm) Ag (x nm) ZnO (50 nm) was selected with Ag layer of varying thickness (x = 5, 10, 14, 20, 30, and 40 nm). The dosimetric properties were investigated where samples were irradiated with X-ray doses in the range of 0.01–4 Gy. The optimum TL intensity found at ZnO (200 nm), Ag (10 nm) ZnO (50 nm) . The glow curve revealed a single peak, the dosimetric peak consistent to 230 °C. In contrast, the best heating rate and annealing temperature and time recorded 3 °C/s, 200 °C, and 30 min respectively. The dose-response demonstrated good linearity within the dose range of 0.01–4 Gy. The other properties have been studied, such as reused, thermal fading, and optical fading; the results in this study revealed that the new host dosimeter exhibits a suitable TL property for radiation detection. The Photoluminescence PL study depicted two sharp peaks of ZnO/Ag/ZnO multilayer thin films at both visible regions at 740–810 nm and UV region of 380 nm (band-edge), corresponding to deep-level emission (DLE) and exciton emission respectively. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive x-ray (EDX), and Ultra-Violet Visible (UV–Vis) were utilized to study crystalline structure, morphology, and element composites and optical properties respectively. • ZnO/Ag/ZnO multilayer system grown successfully by (RF/DC) sputtering. • The glow curve revealed a single peak corresponding with dosimetric peak located at 230 °C. • Photoluminescence and thermoluminescence properties have been investigated. • The multilayer system demonstrates remarkable repeated irradiation reproducibility without pre-irradiation. • The best heating rate and annealing temperature and time recorded 3 °C/s, 200 °C, and 30 min.

Crystallographic and Judd-Ofelt Parametric investigation into Ca9Bi(VO4)7:Eu3+ nanophosphor for NUV-WLEDs

Judd-Ofelt theoretical approach and Rietveld refinement technique are implemented to gain a profound insight of remarkable structural and optoelectronic aspects of Eu3+-doped Ca9Bi(VO4)7 nanophosphor. The bright red emitting vanadate-based series was developed via an efficient route of solution combustion synthesis (SCS). The Rietveld refinement, been employed upon powder X-ray diffraction (PXRD) patterns of Ca9Bi(VO4)7 and Ca9Bi0.30Eu0.70(VO4)7 confirmed the purity of phase and structural prototype as trigonal with R3c(161) space group symmetry. The synthesized sample underwent transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FE-SEM) for morphological analysis while elemental composition was determined through energy dispersive X-ray (EDX) analysis. The experimental value of band gap for host Ca9Bi(VO4)7 was found to be 3.28 eV. The intense emission of bright red region was abided by CIE chromaticity coordinates (x = 0.6403, y = 0.3592). The refractive index value of host is 2.76 and a meticulous study of photoluminescence PL emission spectra was performed to obtain Judd-Ofelt intensity parameters, specifically Ω2 (= 3.429 × 10−20) and Ω4 (= 0.351 × 10−20), quantum efficiencies and radiative rates for 5D0 term. The structural and optoelectronic outcomes present Ca9Bi0.30Eu0.70(VO4)7 phosphor as a strong contender for near UV-WLEDs and potential one for laser devices.

Structural and optical effects of low dose rate Co-60 gamma irradiation on PbS thin films

Thin films of lead sulphide (PbS) were grown on the Si (100) and glass substrates using the simple chemical bath deposition (CBD) method. The prepared films had the cubic structure at room temperature, and the thickness was 350 nm at a 120 min deposition time. In this work, the effect of low-dose rate gamma irradiation on the structural and optical characteristics of the prepared thin films was investigated. The PbS thin films were exposed at the National SSDL (Secondary Standard Dosimetry Laboratory) using gamma beam emitted from Co-60 source, the average energy of the photon beam was 1.25 MeV. Here, four different doses (1, 2, 3 and 4 kGy) were used and the dose rate was about 380 mGy/min. The changes on the optical and structural properties of the PbS films due to the gamma irradiation were evaluated. The results showed that the intensity of photoluminescence PL and the grain size decreased with increasing the radiation dose. This could be related to the changes in the crystalline structural during the experiment. In addition, the band gap obtained by the UV transmittance spectrum was confirmed with the results of XRD. These results could indicate the potential application for PbS film in microelectronic field.

Sensitization of Er3+ NIR emission using Yb3+ ions in alkaline-earth chloro borate glasses for fiber laser and optical fiber amplifier applications

This paper reports on the sensitization of Er3+ ions near infrared emission (1.54 μm) using Yb3+ as a sensitizer in alkaline-earth chloro borate (AECB) glasses synthesized by using melting quenching method. The Er3+ NIR emission has been observed in the range 1450−1650 nm with intense peak at 1540 nm upon 381 nm excitation. The effect of Yb3+ ion concentration as sensitizer on NIR emission of Er3+ doped AECB glasses has been investigated in detailed using the photoluminescence excitation (PLE), PL emission and decay spectral studies. The enhancement in the NIR emission upon varying the Yb3+ doping ion concentration has been aptly elucidated through an energy level diagram. To check the suitability of these glasses for laser and fiber amplifier applications, the absorption, emission and gain cross-sections are also evaluated. Relatively higher values of absorption (σacs = 14.6 × 10−21), emission (σecs = 13.72 × 10−21 cm2) and gain cross-sections are observed for 0.5Er3+-1.5Yb3+ AECB optimized glass. The results obtained contemplates the superior nature of Er3+ and Yb3+ co-doped AECB glasses for the laser and fiber amplifier applications.

Synthesis, molecular structure, spectroscopic characterization and antibacterial activity of the pyrazine magnesium porphyrin coordination polymer

Abstract A new material of magnesium(II) polymer compound with the formula {[MgII(TPP)(pz)]• 0.5[MgII(TPP)]•CH2Cl2}n (I), (TPP) = meso‑tetraphenylporphyrinato and pz = pyrazine) was synthetized and characterized by IR, UV-visible, PL photoluminescence and 1H NMR spectroscopy studies, single-crystal XRD analyses and cyclic voltammetry. The crystal structure of (I) is made by the 1D {[Mg(TPP)(pz)]} polymeric chains (molecules I(A)) where the tetracoordinated magnesium(II) complexes [Mg(TPP)] (molecules I(B)) are located as well as the dichloromethane solvent molecules. The crystal packing of (I) is stabilized by intermolecular C H⋯Cg π interactions where Cg is the centroid of phenyl and pyrrole rings. Additionally, the photophysical properties have been evaluated by UV-visible absorption and fluorescence emission spectroscopies. The UV-visible spectrum of (I) shows a redshift Soret band value (428 nm) compared to that of the free base H2TPP porphyrin while the λmax values of the Q bands are in the range 560 – 610 nm. The optical gap of (I) was estimated at 1.99 eV. The cyclic voltammogram of the title compound presents two reversible oxidation waves and one reversible reduction wave. The HOMO and LUMO energy values were deduced from the voltammogram which are -4.96 and -2.85 eV respectively. Furthermore, bioactivity investigations revealed that the free porphyrin, the starting material [MgII(TPP)] and complex (I) could be used as potential antibacterial agents.

Hydrothermal synthesis and optical properties of Fe doped ZnO nanorods

ZnO nanopowders with hexagonal wurtzite structure were synthesized by hydrothermal method with different concentrations of Fe. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy The morphology, structure and optical properties of the samples were tested and characterized by XPS and (photoluminescence) PL spectra.The results show that the crystal structure of wurtzite ZnO does not change with the increase of Fe doping concentration, and Fe ions do not change into ZnO lattice instead of Zn ions. At the same time, the uniformity of flower-like ZnO nanorods deteriorates, Fe doping A small number of single nanorods with smaller sizes appeared in the hetero-ZnO nanorods.The PL spectrum shows that as the Fe doping concentration increases, the UV luminescence peak of the sample does not change significantly, and the intensity of the luminescence peak decreases first and then increases, indicating that the defect of the sample first decreases and then increases.When the concentration of Fe doping is 1.5%, the prepared ZnO flower-like nanorods have a relatively low visible luminescence peak, which has a small defect.

Effect of different temperatures to remove reduction gas on the photoluminescence properties of Eu-doped Li2 (Ba1-x Srx )SiO4 phosphors.

In this study, Eu-doped Li2 (Ba1-x Srx )SiO4 powders (x = 0, 0.2, 0.4, and 0.6) were synthesized at 850°C in a reduction atmosphere (5% H2 + 95% N2 ) for a duration of 1 h using a solid-state reaction method. The reduction atmosphere was infused as the synthesis temperature reached 850°C, and was removed as the temperature dropped to 800-500°C. Li2 (Ba1-x Srx )SiO4 (or Li2 BaSiO4 ), (Ba,Sr)2 SiO4 (or BaSiO4 ), and Li4 SiO4 phases co-existed in the synthesized Eu-doped Li2 (Ba1-x Srx )SiO4 powders. A new finding was that the reduction atmosphere removing (RAR) temperature of the Li2 (Ba1-x Srx )SiO4 phosphors had a large effect on their photoluminescence excitation (PLE) and PL properties. Except for the 800°C-RAR-treated Li2 BaSiO4 phosphor, PLE spectra of all other Li2 (Ba1-x Srx )SiO4 phosphors had one broad emission band with two emission peaks centred at ~242 and ~283 nm; these PL spectra had one broad emission band with one emission peak centred at 502-514 nm. We showed that the 800°C-RAR-treated Li2 BaSiO4 phosphor emitted a red light and all other Li2 (Ba1-x Srx )SiO4 phosphors emitted a green light. Reasons for these results are discussed thoroughly.

Effects of Annealing Process on the WO3 Thin Films Prepared by Pulsed Laser Deposition

This work presents a study of the effect of annealing temperature on the optical and structural properties of WO3 that has been deposited by Pulsed Laser Deposition (PLD) method at 300°C on the rules of glass and indicates the effect of annealing temperatures 350, 450 and 550°C for one hour on those properties. The results of X-Ray diffraction showed all the films prepared with the installation of multi-crystalline tetragonal and directional prevalent (010) for all models after annealing. The annealing led to an increase in the grain size. Full width at half maximum FWHM values of the (010) peaks of these films decreased from 1.492° to 1.064° with increasing annealing temperature, and the highest value of the specific surface area was 63 m2/gm. The natural structure of the WO3 nanoparticles films were studied by using field emission scanning electron microscopy (FESEM), it revealed that the average grain size increased with increasing of annealing temperature from 46.57 to 485.1nm. The optical features of the films were studied by Photoluminescence PL, the results gave one emission peaks located at 437 nm, and there was a red shift when the annealing temperatures were increased.

Effect of low dose-rate industrial Co-60 gamma irradiation on ZnO thin films: Structural and optical study

The effect of low-dose rate gamma rays irradiation on ZnO thin films of different thicknesses has been studied. Preferentially oriented (002) ZnO thin films have been deposited on Si (100) and glass substrates using radio frequency magnetron sputtering. ZnO films with c-axis-oriented Würtzite structure were obtained at room temperature. ZnO films with thickness of 200 nm and 600 nm were prepared and studied. The prepared films were irradiated using1.25-MeV gamma beam emitted from Cobalt sources (Co-60) with two different doses (2and 4 kGy) and the effect of the gamma irradiation on the optical and structural properties of the ZnO films was examined. The photoluminescence PL intensity was found to increase with the increasing of the irradiation dose in both thin and thick films. This finding allows improving the scintillation output signal of the material while keeping grain size unchanged if low dose rate irradiation is used, as X-ray diffraction patterns showed. Raman spectrum correlates with XRD results. The band gap extracted by UV transmittance spectrum was also identified. • Effect of low-dose rate gamma rays irradiation on ZnO thin films was studied. • ZnO thin films with different thicknesses were used. • Photoluminescence intensity increased with the increase of the irradiation dose for all films. • Improving the scintillation output signal of the material while keeping grain size unchanged. • The band gap extracted by UV transmittance spectrum was also identified.

Structure and photoluminescence characteristics of mixed nickel–chromium oxides nanostructures

In this work, nickel–chromium-layered double hydroxide (Ni(II)–Cr(III)LDH) is prepared via co-precipitation method at room temperature with 1:2:3 molar ratio of CrCl3·6H2O: NiCl2·6H2O: NaCl using sodium hydroxide as a precipitating agent. Ni(II)–Cr(III) LDH is synthesized in the absence and in the presence of functionalized amino-organic compounds such as acetamide, glycine, and urea. The ratio between CrCl3·6H2O: NiCl2·6H2O: NaCl: acetamide, glycine or urea was 1:2:3:6. The mixed nickel–chromium oxide nanoparticles are prepared by the calcination of Ni(II)–Cr(III) LDHs at 600 ℃ for 2.5 h. Ni(II)–Cr(III) LDHs and mixed Ni(II)–Cr(III) oxides nanoparticles are characterized by several techniques including FTIR, TGA, XRD, FESEM, HRTEM, and PL. Functionalized amino-organic compounds improve the thermal stability in the order of glycine > urea > acetamide. Also, it affects photoluminescence PL intensity which indicates a marked reduction in electron–hole recombination with the highest photocatalytic activity compared to visible light-driven H2 and O2 evolution. The resulting mixed Ni(II)–Cr(III) oxides particles have an amorphous structure and a relatively uniform size of below 10 nm.

Structural and optical properties of LSO scintillator-polymer composite films

Abstract Composite films containing homogeneously dispersed scintillation nano-particles of Lu2SiO5:Ce3+, in optically transparent polymer matrix, have been prepared and characterized through X-ray diffraction, Thermogravimetric analysis TGA, electron scanning microscopy morphology SEM and PL photoluminescence. Lu2SiO5:Ce3+ scintillator powder was successfully synthesized via Sol-Gel method. This study is realized with different mass ratios of nano-particles embedded in polystyrene and polylactic acid polymer matrix (5, 10, 15, 20%) to see the influence of nano-particles on the mechanical, structural and optical properties of films. The composites have been prepared with 200 μm thickness. It’s found that the structural proprieties change with mass ratio on each sample. PL photoluminescence show the characteristic Lu2SiO5:Ce3+ emission in the blue region and intensity varied for each film.

Corresponding relation between PL of multicrystalline silicon wafers and solar cell efficiency

Various market factors (e.g., anti-dumping and anti-bribery, subsidy retreat, etc.) have accelerated technology upgrading and cost efficiency of PV industry. Improving conversion efficiency is an effective way to reduce cost. Mainstream silicon manufacturers are intensifying research and development of next generation high-efficiency multicrystalline silicon wafer that is of higher efficiency. It is essential to obtain the cell efficiency parameters at silicon wafer-side. This work analyzes the relationship between PL image parameters of multicrystalline silicon measured by photoluminescence tester (PL) and the corresponding cell conversion efficiency, and the relationship between parameters of PL image and cells. Firstly, an analysis software is independently compiled to analyze the black silk and normalized intensity parameters of PL image, with the numerical results of the corresponding silicon wafers calculated. Selected high efficiency multicrystalline silicon bricks are cut into silicon wafers of 190 μm thickness, which are put to tests sequentially on the PL images of multicrystalline silicon wafers and then made into solar cells. The producing process of solar cells includes ordinary acid texturing, diffusion, removal of phosphosilicon silicon glass (PSG), plasma chemical vapor deposition (PECVD), screen printing, etc. Then cell efficiency and V oc parameters thereof are tested, with the correspondence between cell efficiency and parameters thereof and the PL parameters. The experimental data show that the tail is mainly affected by large grain boundaries and high impurity content. The correlation deviation of the cell efficiency, normalized strength of V oc and PL images, and black silk ratio parameters are greater than those of the middle section and the head. The black silk ratio is low, and its solar cells efficiency and V oc are high. The normalized strength of PL images is high, and its solar cells efficiency and V oc are high. But the normalized strength of PL images and V oc of cell have strong correlation with black silk ratio of PL images, and the normalized strength and black silk ratio of PL images have weak correlation with cell conversion efficiency. The reason is that material properties of PL photoluminescence test silicon are related to the corresponding cell V oc, and cell conversion efficiency is affected by many factors: texture, diffusion, coating processes, etc. In this paper, the expression of normalized strength of PL and cell V oc is deduced based on the semiconductor correlation principle. It is proved that the normalized strength of PL is strongly correlated with that of cell V oc in principle. The normalized strength of PL obtained by the analysis has the closest correlation with the quality of multicrystalline silicon wafers, which can be better used to guide the quality improvement of multicrystalline silicon wafers.

Synthesis, Characterization of New Polyamides Bearing Triarylamine for Lightemitting Diodes

In this work, new di-acid monomers 4, 4’-di-carboxillic-4”-bromo-2”, 6”-dimethyl triphenylamine (Ma), 4, 4’- di-carboxylic -4”-chloro-2”, 6”-dimethyl triphenylamine (Mb) and 4, 4’- di-carboxylic -2”,4”-dichloro-6”-methyl triphenylamine (Mc) were synthesized by reaction of p-cyanobenzofluride with three different aromatic amines (4-bromo,2,6-dimethyl aniline, 4-chloro,2,6-dimethyl aniline and 2,4 dichloro, 6- methyl aniline ) via aromatic nucleophilc substitution method to form three di cyano intermediates 4, 4’-Dicyano-4”-bromo-2”, 6”-dimethyl triphenylamine (Da), 4, 4’-dicyano-4”-chloro-2”, 6”-dimethyl triphenylamine (Db) and 4, 4’-dicyano-2”,4”-dichloro-6”-methyl triphenylamine (Dc) which form final di-carboxylic monomers after alkaline hydrolysis. Finally, these monomers react with two different aromatic di amines, phenylene diamins and benzidine respectively via polycondensation reaction to form final polyamides 4"-bromo-2", 6"-dimethyl-triphenylamine-4, 4'-polyphenylbenzamide (Pa), 4”-chloro-2”,6”-dimethyl- triphenylamine-4,4'-polyphenylbenzamide (Pb), 2”,4”-dichloro-6”-methyl-triphenylamine 4,4'- polyphenylbenzamide (Pc),4"-bromo-2",6"-dimethyl triphenylamine-4,4'- polyphenylbiphenylamide (Pd), 2”,4”-dichloro-6”-methyl-triphenylamine-4,4’-polyphenylamide (Pf).&#x0D; The chemical structure of these polymers characterized by FTIR and NMR techniques. All the results of polyamides showed excellent solubility in most polar solvents to form strong thin films. The polyamides possess a good thermal stability with height glass transition temperatures (Tg).&#x0D; Polyamides in DMSO solvent gave strong photoluminescence PL. Thin casting films of these polyamides in cyclic voltammetry (C.V) on glass base of iridium-tin oxide (ITO) as working electrode in dry CH3CN solvent contains 0.1 M of tetrabutylantimoneperchlorate (TBAP) as an&#x0D; Electrolyte gave one redox wave.

Preparation and Characteristics Study of Polystyrene/Porous Silicon Photodetector Prepared by Electrochemical Etching

Novel doped polystyrene (PS)/porous silicon (PSi) heterojunction photodetector prepared by solution cast and electrochemical techniques is proposed here. The structural and optical properties of polystyrene film and porous silicon surface were investigated using X-ray diffraction (XRD), scanning electron microscope, Fourier transformed infrared (FT-IR), and UV–Vis spectrophotometer. XRD data confirmed that the PS film was amorphous in nature and the porous silicon was nanocrystalline. The optical properties showed that the average optical transmittance and the optical energy gap of PS film were 80% and 3.2 eV, respectively. The electrical properties revealed that the electrical resistivity and mobility of the doped polystyrene film were 3 × 104 Ω cm and 4.5 × 10−5 cm2 V−1 s−1, respectively. Photoluminescence PL of porous silicon was investigated. Dark I–V characteristics revealed that the PS/PSi heterojunctions prepared with an etching time of 5 min exhibited better-rectifying properties than that of PS/PSi heterojunction prepared at 10 min. The figures of merit of the photodetectors such as spectral responsivity, external quantum efficiency, and detectivity were investigated and compared with Au/PSi Schottky photodetectors. Minority carrier lifetime of the photodetectors was measured using open circuit voltage decay method.

Synthesis of Black Phosphorus Quantum Dots with High Quantum Yield by Pulsed Laser Ablation for Cell Bioimaging.

Black phosphorus quantum dots (BPQDs), with an average diameter of about 6 nm and a height of about 1.1 nm, are successfully synthesized by means of a pulsed laser ablation (PLA) method in isopropyl ether (IPE) solvent. The photoluminescence PL quantum yield of the as-prepared sample is as high as 20.7 %, which is 3 times that of BPQDs prepared by means of probe ultrasonic exfoliation (approximately 7.2 %). The stable and blue-violet PL emission of the BPQDs is observed. It can be elucidated that electrons transit from the LUMO energy level to the HOMO energy level, as well as energy levels below the HOMO (H1 and H2). In addition, BPQDs are also utilized in bioimaging in HeLa cells, showing an intense and stable PL signal and excellent biocompatibility. Hence, this work indicates that the obtained BPQDs with high quantum yield and stable PL emission have great potential for biomedical applications, including biolabeling, bioimaging, and drug delivery.

Comparison of performance and optoelectronic processes in ZnO and TiO2 nanorod array-based hybrid solar cells

Abstract The reported efficiencies of pristine ZnO nanorod array (NRA)-based polymer-inorganic hybrid solar cells (HSCs) are normally lower than those of their pristine TiO2 NRA-based counterparts. This difference typically results from the lower short-circuit current density (Jsc) of the ZnO NRA device. This paper presents a comparative study of pristine ZnO and TiO2 NRA-based HSCs. We investigate the morphological structure (length, diameter, number density, area of nanorod laterals), photovoltaic performance (current density-voltage J–V, external quantum efficiency EQE), and optoelectronic processes related to electron transfer (electron mobility μe, electron diffusion length LD, electron lifetime τe and electron transit time τt related electron collecting efficiency ηcc, electron injection ηinj, surface potential SP, photoluminescence PL, bound charge pairs BCP) in HSCs, with ZnO and TiO2 NRA as electron acceptor. Our comparative investigations reveal that the factors relating to the interface area, μe, LD, and ηcc are not the key factors responsible for the difference in the value of Jsc in ZnO and TiO2 NRA-based HSCs with the same device structure. In fact, the crucial step for a lower Jsc in ZnO NRA-based HSCs than in TiO2 NRA-based HSCs is attributed to the less efficient transfer of photo-generated electrons at the charge separation interface in ZnO NRA-based HSCs. Dynamic characterizations indicate that the transfer of interfacial photo-generated electrons in TiO2 NRA-based HSCs is more efficient than ZnO NRA-based HSCs, and is confirmed by Kelvin probe force microscopy (KPFM) and PL studies. The reason for the better interface charge transfer property in MEH-PPV/TiO2 NRA than that of in MEH-PPV/ZnO NRA is further investigated by Marcus model, we find that more trapped BCP states are generated in the ZnO NRA based HSCs, which resulting in lower interfacial electron injection efficiency from polymer to ZnO NRA.

Synthesis of SiC nanoparticles by SHG 532 nm Nd:YAG laser ablation of silicon in ethanol

In this work, colloidal spherical nanoparticles NPs of silicon carbide SiC have been synthesized using second harmonic generation 532 nm Nd:YAG laser ablation of silicon target dipped in ethanol solution at various laser fluences (1.5–5) J/cm2. X-Ray diffraction XRD, scanning electron microscopy SEM, transmission electron microscope TEM, Fourier transformed infrared spectroscopy FT-IR, Raman spectroscopy, photoluminescence PL spectroscopy, and UV–Vis absorption were employed to examine the structural, chemical and optical properties of SiC NPs. XRD results showed that all synthesised SiC nanoparticles are crystalline in nature and have hexagonal structure with preferred orientation along (103) plane. Raman investigation showed three characteristic peaks 764,786 and 954 cm−1, which are indexing to transverse optic TO phonon mode and longitudinal optic LO phonon mode of 4H-SiC structure. The optical absorption data showed that the values of optical energy gap of SiC nanoparticles prepared at 1.5 J/cm2 was 3.6 eV and was 3.85 eV for SiC synthesised at 5 J/cm2. SEM investigations confirmed that the nanoparticles synthesised at 5 J/cm2 are agglomerated to form larger particles. TEM measurements showed that SiC particles prepared at 1.5 J/cm2 have spherical shape with average size of 25 nm, while the particles prepared at 5 J/cm2 have an average size of 55 nm.