Anver Aziz

Growth of Zn1−x Cd x O nanocrystalline thin films by sol-gel method and their characterization for optoelectronic applications

This paper describes the growth of Cd doped ZnO thin films on a glass substrate via sol-gel spin coating technique. The effect of Cd doping on ZnO thin films was investigated using X-ray diffraction (XRD), UV-Vis spectroscopy, photoluminescence spectroscopy, I–V characteristics and field emission scanning electron microscopy (FESEM). X-ray diffraction patterns showed that the films have preferred orientation along (002) plane with hexagonal wurtzite structure. The average crystallite sizes decreased from 24 nm to 9 nm, upon increasing of Cd doping. The films transmittance was found to be very high (92 to 95 %) in the visible region of solar spectrum. The optical band gap of ZnO and Cd doped ZnO thin films was calculated using the transmittance spectra and was found to be in the range of 3.30 to 2.77 eV. On increasing Cd concentration in ZnO binary system, the absorption edge of the films showed the red shifting. Photoluminescence spectra of the films showed the characteristic band edge emission centred over 377 to 448 nm. Electrical characterization revealed that the films had semiconducting and light sensitive behaviour.

Influence of zinc concentration on band gap and sub-band gap absorption on ZnO nanocrystalline thin films sol-gel grown

Abstract ZnO thin films were fabricated on quartz substrates at different zinc acetate molar concentrations using sol-gel spin coating method. The samples were characterized using X-ray diffraction, field emission scanning electron microscope, UV-Vis spectroscopy, FT-IR spectroscopy and photoluminescence spectroscopy. Sub-band gap absorption of ZnO thin films in the forbidden energy region was carried out using highly sensitive photothermal deflection spectroscopy (PDS). The absorption coefficients of ZnO thin films increased in the range of 1.5 eV to 3.0 eV, upon increasing zinc concentration. The optical band gaps were evaluated using Tauc’s plots and found to be in the range of 3.31 eV to 3.18 eV. They showed the red shift in the band edge on increase in zinc concentration. The PL spectra of ZnO thin films revealed the characteristic band edge emission centered at the 396 nm along with green emission centered at the 521 nm.

Structural and optical modification in 4H-SiC following 30 keV silver ion irradiation

The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low energy ion irradiation and should be addressed while fabricationg devices based on SiC for outer space application. Additionally, this study provides a platform for introducing structural and optical modification in 4H-SiC using ion beam technology in a controlled manner.The market of high power, high frequency and high temperature based electronic devices is captured by SiC due to its superior properties like high thermal conductivity and high sublimation temperature and also due to the limitation of silicon based electronics in this area. There is a need to investigate effect of ion irradiation on SiC due to its application in outer space as outer space is surrounded both by low and high energy ion irradiations. In this work, effect of low energy ion irradiation on structural and optical property of 4H-SiC is investigated. ATR-FTIR is used to study structural modification and UV-Visible spectroscopy is used to study optical modifications in 4H-SiC following 30 keV Ag ion irradiation. FTIR showed decrease in bond density of SiC along the ion path (track) due to the creation of point defects. UV-Visible absorption spectra showed decrease in optical band gap from 3.26 eV to 2.9 eV. The study showed degradation of SiC crystallity and change in optical band gap following low...

Sol-Gel Derived Cds Nanocrystalline Thin Films: Optical and Photoconduction Properties

Abstract High-quality CdS nanocrystalline thin films were grown by sol-gel spin coating method at different solution temperatures on glass substrates. As-deposited films exhibited nanocrystalline phase with hexagonal wurtzite structure and showed good adhesion and smooth surface morphology. It was clearly observed that the crystallinity of the thin films improved with the increase in solution temperature. Crystallites sizes of the films also increased and were found to be in the range of 10 mm to 17 nm. The influence of the growth mechanism on the band and sub-band gap absorption of the films was investigated using UV-Vis and photothermal deflection spectroscopy (PDS). The band gap values were calculated in the range of 2.52 eV to 2.75 eV. The band gap decreased up to 9 % with the increase in solution temperature from 45 °C to 75 °C. Absorption coefficients estimated by PDS signal showed the significant absorption in low photon energy region of 1.5 eV to 2.0 eV. The dark and illuminated I-V characteristics revealed that the films were highly photosensitive. The results demonstrated the potential applications of sol-gel grown CdS nanocrystalline thin films as photoconductors and optical switches.

Numerical simulations of perovskite thin-film solar cells using a CdS hole blocking layer

In this work, the numerical simulation of CH3NH3PbI3 perovskite solar cells was undertaken using the scaps-1d solar cell capacitance simulator software. A perovskite solar cell was simulated for best efficiency by replacing the traditional compact TiO2 layer with CdS (i.e., a hole-blocking layer) because CdS layers have been shown to possess a greater photostability than TiO2 with continuous illumination of sunlight. With the view of optimizing the device fabrication of perovskite/CdS thin-film solar cell (TFSC) for maximum efficiency, the perovskite/CdS TFSC structure was optimized theoretically using scaps-1d, which is possible because the perovskite layer has the same configuration and an excitation type as CdTe, copper-indium-gallium-selenide, and other inorganic semiconductor solar cells. Solar cell performance is highly dependent on the layer parameters, and so the effect that absorber thickness, bulk defects, and interface defects have on the device performance was studied and the device was optimized. Further, the effect that atmospheric conditions have on device performance was studied by varying the temperature and illumination density, and the optimum performance was found. After these optimizations, the simulation results show that a perovskite thickness of 500 nm yields an efficiency of 23.83% with a high open-circuit voltage of 1.37 V. These results for this absorber thickness is in good agreement with reports of experimental results for this device.In this work, the numerical simulation of CH3NH3PbI3 perovskite solar cells was undertaken using the scaps-1d solar cell capacitance simulator software. A perovskite solar cell was simulated for best efficiency by replacing the traditional compact TiO2 layer with CdS (i.e., a hole-blocking layer) because CdS layers have been shown to possess a greater photostability than TiO2 with continuous illumination of sunlight. With the view of optimizing the device fabrication of perovskite/CdS thin-film solar cell (TFSC) for maximum efficiency, the perovskite/CdS TFSC structure was optimized theoretically using scaps-1d, which is possible because the perovskite layer has the same configuration and an excitation type as CdTe, copper-indium-gallium-selenide, and other inorganic semiconductor solar cells. Solar cell performance is highly dependent on the layer parameters, and so the effect that absorber thickness, bulk defects, and interface defects have on the device performance was studied and the device was optimi...

Correction to: Electronic Structure, Optical and Transport Properties of Double Perovskite La2NbMnO6: A Theoretical Understanding from DFT Calculations

Authors Khursheed Ahmad Parrey and Shakeel Ahmad Khandy included the names of Asad Niazi, Anver Aziz, and S. G. Ansari as co-authors of this article without their permission.

Numerical modelling of CIGS/CdS solar cell

In this work, we design and analyze the Cu(In,Ga)Se2 (CIGS) solar cell using simulation software “Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D)”. The conventional CIGS solar cell uses various layers, like intrinsic ZnO/Aluminium doped ZnO as transparent oxide, antireflection layer MgF2, and electron back reflection (EBR) layer at CIGS/Mo interface for good power conversion efficiency. We replace this conventional model by a simple model which is easy to fabricate and also reduces the cost of this cell because of use of lesser materials. The new designed model of CIGS solar cell is ITO/CIGS/OVC/CdS/Metal contact, where OVC is ordered vacancy compound. From this simple structure, even at very low illumination we are getting good results. We simulate this CIGS solar cell model by varying various physical parameters of CIGS like thickness, carrier density, band gap and temperature.

Study of CdTe/CdS solar cell at low power density for low-illumination applications

In this paper, we numerically investigate CdTe/CdS PV cell properties using a simulation program Solar Cell Capacitance Simulator in 1D (SCAPS-1D). A simple structure of CdTe PV cell has been optimized to study the effect of temperature, absorber thickness and work function at very low incident power. Objective of this research paper is to build an efficient and cost effective solar cell for portable electronic devices such as portable computers and cell phones that work at low incident power because most of such devices work at diffused and reflected sunlight. In this report, we simulated a simple CdTe PV cell at very low incident power, which gives good efficiency.

Effect of nitrogen ion implantation on the structural and optical properties of indium oxide thin films

: We report here synthesis and subsequent nitrogen ion implantation of indium oxide (In2O3) thin films. The films were implanted with 25keV N+ beam for different ion doses between 3E15 to 1E16 ions/cm2. The resulting changes in structural and optical properties were investigated using XRD, SEM-EDAX and UV-Vis Spectrometry. XRD studies reveal decrease in crystallite size from 20.06 to 12.42 nm with increase in ion dose. SEM micrographs show an increase in the grain size from 0.8 to 1.35 µm with increase in ion dose because of the agglomeration of the grains. Also, from EDAX data on pristine and N-implanted thin films the presence of indium and oxygen without any traces of impurity elements could be seen. However, at lower ion doses such as 3E15 and 5E15 ions/cm2, no evidence of the presence of nitrogen ion was seen. However, for the ion dose of 1E16 ions/cm2, evidence of presence of nitrogen can be seen in the EDAX data. Band gap calculations reveal a decrease in band gap from 3.54 to 3.38eV with increasin...

Structural, optical and electrical properties of tin oxide thin films for application as a wide band gap semiconductor

Tin oxide (SnO) thin films were synthesized using thermal evaporation technique. Ultra pure metallic tin was deposited on glass substrates using thermal evaporator under high vacuum. The thickness of the tin deposited films was kept at 100nm. Subsequently, the as-deposited tin films were annealed under oxygen environment for a period of 3hrs to obtain tin oxide films. To analyse the suitability of the synthesized tin oxide films as a wide band gap semiconductor, various properties were studied. Structural parameters were studied using XRD and SEM-EDX. The optical properties were studied using UV-Vis Spectrophotometry and the electrical parameters were calculated using the Hall-setup. XRD and SEM confirmed the formation of SnO phase. Uniform texture of the film can be seen through the SEM images. Presence of traces of unoxidised Sn has also been confirmed through the XRD spectra. The band gap calculated was around 3.6eV and the optical transparency around 50%. The higher value of band gap and lower value o...