Effects of annealing temperature on the structural and optical properties of ZnO hexagonal pyramids

ZnO thin films were deposited on quartz substrate at 550 degrees C by using spray pyrolysis method and subsequently annealed between 600-900 degrees C with a step of 100 degrees C. The characterizations of the structural and optical properties of the films have been carried out by means of X-ray diffraction, scanning electron microscopy (SEM) and optical transmittance measurements. XRD ans SEM images indicated that annealing temperature did not play a great role on the microstructure of ZnO films. ZnO thin films are all in hexagonal crystallographic phase and have (0 0 2) preferred orientation, regardless of the annealing temperature. However, SEM studies showed that there exist a high density of micro-rods in the shape of hexagonal pyramid with the width in the order of about 1 mu m and height in range of 1-3 mu m and the adjacent hexagonal crystals to start fusing with each other along their boundaries at high temperatures. As a result of the optical measurements, it was observed that the films show the low transmittance and optical band gap decreases from 3.15 to 3.10eV with the increasing of the annealing temperatures up to 800 degrees C and followed by an increase to 3.20 eV upon further annealing at 900 degrees C

Effects of CdCl2 treatment on properties of CdTe thin films grown by evaporation at low substrate temperatures

The structural, morphological and optical properties of vacuum-evaporated CdTe thin films were investigated as a function of substrate temperature and post-deposition annealing without and with CdCl2/treatment at 400 degrees C for 30 min. Diffraction patterns are almost the same exhibiting higher preferential orientation corresponding to (111) plane of the cubic phase. The intensity of the (111) peak increased with the CdCl2/annealing treatment. The microstructure observed for all films following the CdCl2/annealing treatment are granular, regardless of the as-deposited microstructure. The grain sizes are increased after the CdCl2/annealing treatment but now contain voids around the grain boundaries. The optical band gaps, E-g, were found to be 1.50, 1.50 and 1.48 eV for films deposited at 200 K and annealed without and with CdCl2/treatment at 400 degrees C for 30 min respectively. A progressive sharpening of the absorption edge upon heat treatment particularly for the CdCl2/treated was observed

Structural, optical and electrical properties of Al-doped ZnO microrods prepared by spray pyrolysis

Al-doped ZnO thin films were obtained on glass substrates by spray pyrolysis in air atmosphere. The molar ratio of Al in the spray solution was changed in the range of 0-20 at.% in steps of 5 at.%. X-ray diffraction patterns of the films showed that the undoped and Al-doped ZnO films exhibited hexagonal wurtzite crystal structure with a preferred orientation along (002) direction. Surface morphology of the films obtained by scanning electron microscopy revealed that pure ZnO film grew as quasi-aligned hexagonal shaped microrods with diameters varying between 0.7 and 1.3 mu m. However, Al doping resulted in pronounced changes in the morphology of the films such as the reduction in the rod diameter and deterioration in the surface quality of the rods. Nevertheless, the morphology of Al-doped samples still remained rod-like with a hexagonal cross-section. Flower-like structures in the films were observed due to rods slanting to each other when spray solution contained 20 at.% Al. Optical studies indicated that films had a low transmittance and the band gap decreased from 3.15 to 3.10 eV with the increasing Al molar ratio in the spray solution from 0 to 20 at.%

The Investigation of Current-Conduction Mechanisms of Te/NaF:CdS/SnO2 Structure in Wide Temperature Range of 80–400 K

© 2017, The National Academy of Sciences, India.In order to interpret the current-conduction mechanisms of the Te/NaF:CdS/SnO2 structure, current–voltage (I–V) measurements were carried out in the temperature range of 80–400 K. Experimental results show that the main electrical parameters such as reverse-saturation current (I0), ideality factor (n) and zero-bias barrier height (ϕB0) values were found to be strong functions of temperature. The I0, n and ϕB0 values were found as 3.16 × 10−12 A, 17.84 and 0.232 eV at 80 K and 2.85 × 10−7 A, 1.40 and 0.877 eV at 400 K, respectively. Therefore, we have attempted to draw ϕB0 versus q/2kT plot in order to obtain the evidence of a Gaussian distribution of the barrier heights (BHs) and this plot shows two straight lines with different slopes. From these plots, mean BH (ϕ¯ B 0) = 0.673 eV and zero-bias standard deviation (σs) = 0.079 V in the first region (80–170 K), ϕ¯ B 0= 1.279 eV and σs = 0.160 V in the second region (200–400 K) have been obtained, respectively. The values of Richardson constant (A*) were obtained from the modified Richardson plot as 21.43 A cm−2 K−2 (200–400 K) and 16.07 A cm−2 K−2 (80–170 K), respectively. This 21.43 A cm−2 K−2 value of A* for the first region is in very close agreement with the known theoretical value of 23 A cm−2 K−2 for n-type CdS. It has been concluded that the temperature dependent I–V characteristics of the Te/NaF:CdS/SnO2 structure can be successfully explained by the basis of thermionic emission mechanism with double Gaussian distribution of the BHs rather than other mechanisms

Electrodeposition of Si-DLC nanocomposite film and its electronic application

WOS: 000429794700017In this study, a silicon doped diamond-like carbon (DLC) nanocomposite film was deposited electrochemically and it was used to fabricate an Ag/Si-DLC/p-Si metal-interlayer-semiconductor (MIS) Schottky diode. Methanol (CH3OH) was used as carbon and tetraethoxysilane (Si(OC2H5)(4)) as Si source, respectively. Morphology of the film was observed by scanning electron microscopy and continuous surface with numerous lumps spread randomly was observed. Structural and chemical composition analyses of the film were carried out by Raman and X-ray photoelectron spectroscopy. Typical D and G bands of DLC films were not observed in the Raman spectrum due to abundance of Si-C bonds. Silicon incorporation promoted the film deposition and increased sp(3) bonds in the film. Current-Voltage (I-V) measurement was conducted to obtain parameters of the MIS diode. The diode exhibited a good rectifier behavior with similar to 10(3) rectification ratio. In the forward bias semi-logarithmic I-V plot, two linear regions with different slopes were observed. Such behavior was modelled by two parallel diodes and attributed to different conduction mechanism. The main electrical parameters, such as barrier height, ideality factor and series resistance were calculated by I-V and Cheung-Cheung methods. The Si-DLC nanocomposite film acted as barrier height modifier in the MIS diode.Scientific Research Project Committee of Gaziosmanpasa UniversityGaziosmanpasa University [2015/88]This work was supported by the Scientific Research Project Committee of Gaziosmanpasa University (under the Grand contract no: 2015/88)

Enhanced efficiency of CdS/P3HT hybrid solar cells via interfacial modification

Tomakin, Murat/0000-0003-1887-848X; UNVERDI, Ahmet/0000-0001-6144-1158; POLAT, ISMAIL/0000-0002-5134-0246WOS: 000459348400011The present paper examines the effects of surface modification of CdS with diverse dyes on fabricated CdS-based hybrid solar cells. the X-ray diffraction results showed that CdS thin films had a hexagonal phase with a preferred orientation along the (101) plane. Scanning electron microscopy indicated that the CdS specimen was composed of a granular structure while a P3HT layer was formed from tiny grains. Band gaps of the CdS thin films and the P3HT layer were 2.45 eV and 1.98 eV, respectively. the absorption spectra showed that different dye loading caused an increase in the absorbance of CdS thin films in the wavelength range of 400-650 nm. the photoluminescence of the CdS/P3HT structure including various dyes was lower than that of the pristine one, implying that efficient charge separation was achieved upon surface modification. Current density-voltage curves showed that the ITO/CdS/N719/Ag hybrid solar cell exhibited the best overall efficiency of 0.082%, which can be attributed to improvements in both short circuit current density (J(sc)) and open circuit voltage (V-oc). These enhancements can be attributed to the creation of better interfacial contact between CdS and P3HT layers after dye loading.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [116F296]The authors wish to thank the Scientific and Technological Research Council of Turkey (TUBITAK) for its financial support of this work (project number 116F296)

Growth and characterization of Cu2SnS3 (CTS), Cu2SnSe3 (CTSe), and Cu2Sn(S,Se)(3) (CTSSe) thin films using dip-coated Cu-Sn precursor

Kucukomeroglu, Tayfur/0000-0003-4121-9343; OLGAR, MEHMET ALI/0000-0002-6359-8316; Tomakin, Murat/0000-0003-1887-848XWOS: 000475587800080Ternary compounds Cu2SnS3, Cu2SnSe3 and Cu2Sn(S,Se)(3) thin films used in thin film solar cell applications were prepared at the first time by such a two-stage process that includes dip-coating of Cu-Sn precursors as distinct from vacuum-based fabrication methods followed by sulfurization/selenization of prepared precursors via rapid thermal processing at 550 degrees C. All prepared thin films revealed Cu-poor composition. X-ray diffraction and Raman spectra of the samples showed that Cu2SnS3 and Cu2SnSe3 thin films had a monoclinic structure as a dominant phase and additionally some secondary phases such as tetragonal Cu2SnS3 and orthorhombic Cu3SnS4. However, the tetragonal and orthorhombic phases had more impact on Cu2Sn(SSe)(3) thin film. Compact, dense, and small grained surface morphologies were obtained for the Cu2SnS3 and Cu2Sn(SSe)(3) thin films, while the surface morphology of the Cu2SnSe3 thin film had larger grained surface morphology. the Cu2SnS3 thin film demonstrated higher transmittance (similar to 65%) and two different absorption edges that indicates formation of two band gap energy. Band gap values of Cu2SnS3, Cu2Sn(SSe)(3) and Cu2SnSe3 thin films were found 0.97eV (and 1.51eV), 1.25eV and 0.78eV, respectively. the lowest resistivity (2.48x10(-1)Omega cm) and the highest carrier concentration (1.64x10(19)cm(-3)) values were observed for Cu2Sn(SSe)(3) thin film.Recep Tayyip Erdogan University, Rize, TurkeyRecep Tayyip Erdogan University [FDK-2018-964]This work was supported by the research fund of Recep Tayyip Erdogan University, Rize, Turkey, under Contract No. FDK-2018-96

A novel nanostructured CuIn0.7Ga0.3(Se0.4Te0.6)(2)/SLG multinary compounds thin films: For photovoltaic applications

Cankaya, Guven/0000-0003-2932-1695WOS: 000349728500073Investigation on chalcopyrite structures is crucial for making further progress in thin films technology. In this work we present the results on optical, electrical and surface properties of CuIn0.7Ga0.3(Se0.4Te0.6)(2) (CIGSeTe) multinary compounds thin films with annealing effect. The developed procedure is a two-steps methodology involving the pre-reaction of high purity elements Cu, In, Ga, Se and Te in a carbon coated quartz ampoule and e-beam evaporation for thin film deposition. The availability of a multicomponent absorber layers such as CuInGaSeTe, including all elements in a defined ratio, offers the opportunity to reduce film formation temperatures and thereby also reduce manufacturing costs. This aspect was a great motivation to evaluate these materials as banausic and new trend solar cell materials. (C) 2014 Elsevier B.V. All rights reserved.Gaziosmanpasa University Scientific Research ProjectGaziosmanpasa University [2010/12]The authors wish to express sincere appreciation and gratitude to Professor Hasan EFEOGLU from Ataturk University (Electrical and Electronic Engineering) for his assistance and guidance in the preparation of this work, also this work is supported by Gaziosmanpasa University Scientific Research Project (BAP) with the Grand Contract No: 2010/12