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We report on a first-principle theoretical investigation of the optical absorption and emission spectra of poly(3-hexylthiophene) (P3HT) aggregates by means of a multiscale all-atom hybrid approach, which combines: (i) molecular dynamics simulations of (intrachain) conformational and (interchain) positional disorder, (ii) quantum-chemical calculations of intrachain excited states and excitonic interactions, and (iii) solving of a Frenkel–Holstein model that includes coupling of the electronic excitations to a dominant high-frequency molecular vibration. The modeling work points to the co-existence of ordered nano-aggregates into disordered domains, with the former dominating the emission spectrum while both regions contribute to the absorption spectrum. The measured photoluminescence line shape and the Stokes shift are both reproduced by the theory for aggregates comprising polymer chain with lengths ∼35–40 repeating units. [ABSTRACT FROM AUTHOR]

Photophysical properties of diketopyrrolopyrrole derivativessubstituted with oligothiophenes are investigated. All compounds arefound to be fluorescent both in solution and in the solid phase. Atlow temperature in the solid, fluorescence originates from excimer-likeexcited states. Comparison of absorption and fluorescence excitationspectra taken under matrix isolated conditions and on solid filmsshow the presence of both J- and H-type absorption bands in the solidphase. Quantum-chemical calculations, including exciton–phononcoupling to account for deviations from the Born–Oppenheimerapproximation, are performed to simulate the band shape of the lowestabsorption band in the molecular solid. The joint presence of J- andH-bands is explained by the presence of two molecules in the unitcell. The Davydov splitting is substantial for molecules with linearalkyl substituents on the nitrogen atom (on the order of 0.2 eV) butcan be reduced to almost zero by introducing branching at the β-carbonof the alkyl side chain. [ABSTRACT FROM AUTHOR]

Abstract: In this work, hydrogen etching method is applied to improve the quality of nano-crystalline diamond (NCD) films grown from hot-filament assisted chemical vapor deposition (HFCVD) system. From the characteristics of the structure and optical property, the grain size and surface roughness decrease while the optical transmission increase obviously under certain deposition parameters (gas pressure and substrate temperature) and longer etching time. Soft X-ray transmission measurements by synchrotron radiation are also carried out on the NCD films. The result shows that the X-ray transmission has an obvious improvement when the NCD film is fabricated from the hydrogen etching method. And the transmittance reaches 53.3% at X-ray photon energy of 258eV, which has met the requirement for X-ray mask materials. [Copyright &y& Elsevier]

Abstract: The optical and electrical properties of variously textured diamond films have been investigated in this paper. SEM and Raman spectrum indicated that the films produced were of high quality with either (001) or (111) orientation. A four-layer model was used to fit the measured spectroscopic ellipsometry data. The results indicated that the properties of (001)-oriented diamond films were superior to those of (111)-oriented one. The refractive index and extinction coefficient of (001)-oriented diamond film in the infrared region of 2500–12500nm was measured as 2.391 and of the order of 10−5, respectively and that for (111)-oriented one was 2.375 and of the order of 10−4, respectively. The dark current of the (001)-oriented diamond film was measured as 33.7nA for an applied electric field of 100kVcm−1, its resistivity being about 2.33×1010 Ωcm. Current passing through the (001)-oriented diamond film during testing did not change significantly. [Copyright &y& Elsevier]

Abstract: Due to different oriented diamond films having different properties, in this paper optical and electrical properties of different oriented diamond films have been investigated. The measured results indicate diamond films are of high quality and the properties of the (001)-oriented diamond film are better than those of the (111)-oriented one. Refractive index and extinction coefficient of (001)-oriented diamond film in the wavelength range of 2.5–12.5μm is 2.391 and in the order of 10−5, respectively. And for the (111)-oriented one it is 2.375 and in the order of 10−4. The dark current of the (001)-oriented diamond film is 33.7nA under an applied electric field of 100kV/cm. The resistivity of the (001)-oriented diamond film obtained is about 2.33×1010 Ωcm. The current of (001)-oriented diamond film is almost no change with the time testing. [Copyright &y& Elsevier]

Abstract: The surface roughness and optical properties of diamond films untreated and treated by activated hydrogen have been investigated. After hydrogen ion treatment the surface of the film is modified effectively. Optical properties of the treated film are better than those of the untreated one. [Copyright &y& Elsevier]

The electrical performances and optical properties of p-type amorphous silicon oxide (p-SiO x ) thin films with gradient refractive index are studied. The composite thin films as antireflective coatings (ARCs) are widely used in solar cells and microelectronic devices. The double-layer p-SiO x thin films are deposited by plasma-enhanced chemical vapor deposition (PECVD) system. To obtain better optical properties, the refractive index of ARCs can be adjusted by SiH 4 to N 2 O ratio. And the electrical performances of composite thin films can be improved by adjustment of B 2 H 6 to SiH 4 ratio. The computational model is built to predict the optimized range of reflection spectra corresponding to structure of p-SiO x ARCs with gradient refractive index by finite difference time domain (FDTD) method. It shows the difference of reflection spectra with gradient refractive index distribution. The optimized reflection spectra simulated by FDTD method confirms to agree well with that measured by UV–visible spectroscopy. [ABSTRACT FROM AUTHOR]

In this paper, Ag nanoparticles were successfully prepared by chemical reduction, and then Ag/ZnO composite particles were successfully prepared and deposited onto glass substrates to form Ag/ZnO thin films. Hereafter, the structure, the morphology and the metal enhanced fluorescence (MEF) property of Ag nanoparticles and ZnO/Ag composite particles were studied by XRD, SEM, EDS, TEM, UV-vis absorption and fluorescence (FL) spectrometer. The results showed that the average size of Ag nanoparticles increased with the increase of prepared time. Moreover, ZnO layer consisted of polycrystalline structure and amorphous interface layer, but nano-Ag particle was polycrystalline structure. Annealing process was carried out to investigate the influence of annealing process parameters on MEF property of Ag/ZnO composite structure. Due to annealing treatment, the amorphous component of Ag/ZnO thin films was reduced, which might improve the density of Ag/ZnO thin films and the diameter of composite particles. Furthermore, FL enhancement phenomenon of fluorescein isothiocyanate (FITC) molecules might be attributed to the joint influence of the roughness and the density of these films and the average diameter of composite particles. [ABSTRACT FROM AUTHOR]

In this work, B and Ga co-doped ZnO (BGZO) films were fabricated by RF magnetron sputtering method. The effects of substrate temperature on the electrical, optical, structural and morphological properties of B and Ga co-doped ZnO films were investigated. XRD results revealed that deposited films were textured along c-axis and maintain wurtzite crystalline symmetry. As substrate temperature increased up to 200 °C, the film crystallinity was improved and the crystallite sizes became larger. At the substrate temperature of 200 °C, the films showed lower resistivity, higher Hall mobility and higher optical band gap. It was also observed that all films showed high transparency in the visible range (400–800 nm), which did not change obviously with the substrate temperature. [ABSTRACT FROM AUTHOR]

We studied the growth of CuInS2 thin films by single-source evaporation of CuInS2 powder in a high-vacuum system with a base pressure of 10−3 Pa. After evaporation, the films were annealed in a sulfur atmosphere at temperatures from 200 to 500°C for 1h. XRD curves and Raman spectra of the films demonstrated that chalcopyrite CuInS2 was the major crystalline phase. The morphology of Cu x S exhibited a star-like structure, which we report for the first time. The phase composition and optical properties of our polycrystalline thin films were effectively modified by annealing in S. For films annealed at 200 and 350°C, a secondary CuIn11S17 phase appeared, which may be related to solid-state reaction in the S atmosphere. This secondary CuIn11S17 phase has not been widely reported in previous studies. After annealing at 500°C, only a chalcopyrite phase was detected, with bandgap energy of 1.46eV, which is nearly identical to the optimal bandgap energy (1.5eV) of single-crystal CuInS2. This indicates that the composition of the CuInS2 film annealed at 500°C was nearly stoichiometric. The bandgap of the samples first increased and then decreased with increasing annealing temperature, which may be attributed to an increase in grain size, the secondary CuIn11S17 phase, and deviation from stoichiometry. [ABSTRACT FROM AUTHOR]

In this paper, Cu doped CdS thin films were prepared on FTO substrates by RF magnetron sputtering and then were annealed at 350 °C–425 °C in vacuum for 20 min. The influences of different Cu-doped concentrations (Cu 4.1, 5.4, 7.3, 9.1 at%) on morphological, structural, optical properties and photo-electrochemical (PEC) properties of CdS thin films were investigated. The PEC characterizations indicated that the photocurrent densities of CdS:Cu (Cu 4.1, 5.4, 7.3, 9.1 at%) thin films increased from 0.94, 1.28,1.86,1.91 mA cm−2 to 1.33, 1.89, 2.40, 3.16 mA cm−2 after annealing. And the PEC properties of CdS:Cu thin films annealed at different temperatures were also studied. FTO/annealed CdS:Cu/Pt photoanode were fabricated to enhance the photocurrent activity and the photocurrent density of FTO/annealed CdS:Cu/5 nm Pt is 1.5 times larger than that of the CdS:Cu electrode without Pt cocatalyst. • CdS:Cu thin films were firstly prepared by magnetron sputtering method. • PEC properties of n type CdS:Cu thin films were firstly studied. • FTO/CdS:Cu/Pt improved PEC performances of CdS:Cu thin films. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, Cu2FeSnSe4 (CFTSe) sheets were synthesized by a facile solvothermal method for the first time. The structure, morphology, chemical composition and optical properties of the as-synthesized CFTSe sheets were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and UV–vis spectrophotometry. The average particle sizes of the sheets increase with the increasing of the reaction times and temperatures. The band gap of 1.12eV estimated from the UV–vis absorption spectra indicated its suitability for application as absorption layers of thin film solar cells. [Copyright &y& Elsevier]

• Magnesium-doped zinc oxide (MGZO) films are successfully deposited on glass substrates by magnetron sputtering system. • Surface roughness of MGZO film enlarges with substrate temperature increasing. • The band-gap of MGZO film is enhanced by substrate temperature increasing. • The luminescence performance of MGZO film is improved with larger substrate temperature. Magnesium-doped zinc oxide (MGZO) films were deposited on glass substrates by magnetron sputtering system. The effects of substrate temperature on microstructure and optical properties of MGZO films were firstly investigated. Based on XRD results, the full width at half maximum (FWHM) of MGZO film reaches the value of 0.27° at 300 ℃, illustrating the film quality is enhanced via substrate temperature increasing. The band-gap of MGZO film increases with substrate temperature increasing. Alternatively, the photoluminescence quality of MGZO film can be enhanced by the substrate temperature, resulting from the increasing ratio of I 380nm to I 540nm. The ratio achieves the value of 3.2 at 500 ℃. This work can offer a feasible approach to tailor the microstructure and optical properties of MGZO film. [ABSTRACT FROM AUTHOR]

CdTe thin films have been prepared by electrochemical deposition. The morphological, structural, and optical properties of CdTe thin films deposited with different deposition time were investigated, and the influence of film thickness on the photoelectric characteristics of CdTe thin films was studied. At the deposition time of 1.5 h, CdTe thin films had good optical properties and the photocurrent reached 20 μAcm−2. Furthermore, the Pt/CdS/CdTe/FTO structure was prepared to improve its PEC stability and the photocurrent of 240 μAcm−2 had been achieved. [ABSTRACT FROM AUTHOR]