Properties Of CIGS Thin Films Research Articles

Growth mechanism and the properties of CIGS thin films for zero bias photodetector devices

CuInGaSe2 quaternary thin films have been deposited using a single-source, single-step thermal evaporation technique using hydrothermally fabricated CIGS powder. Highly crystalline, homogeneous, and stoichiometric CIGS powder source was prepared by a hydrothermal method and then evaporated at substrate temperatures of room temperature, 150°C, and 300°C. The bulk and surface structural, morphological, and optical properties of the samples were analyzed. The sample deposited at room temperature did not show any phase formation; however, increasing the substrate temperature resulted in the formation of binary and quaternary phases due to interdiffusion of the species. XPS and Raman spectra analysis revealed nanocrystalline Cu2Se phase formation at the interface, while the bulk of the sample remained single-phase CIGS. A higher deposition temperature also facilitated larger grain size and a more compact surface morphology. Increasing the substrate temperature increased the likelihood of interdiffusion of the species from the evaporation flux and controlled the bulk and surface properties of the samples. CIGS/CdS active photodetectors were fabricated by deposition of a CdS buffer layer, with the sample deposited at 150°C showing the highest photocurrent along with low response and recovery times at 0 V bias.

Effects of Annealing Temperature on Structural and Optical Properties Of CIGS Thin Films for Using in Solar Cell Applications

A copper indium0.5gallium0.5selenide2 thin films (CIGS) were deposited at room temperature on glass substrate by thermal evaporation technique. The deposited film were annealed at different annealing temperature (293, 100, 200 and 300)°C. The effect of annealing temperature on structural, optical and electrical properties CIGS films were studied by XRD, UV-Visible absorbance and Hall effect measurements. It is found that the crystallinety enhanced, optical energy gap increases and electrical conductivity decrease with increasing annealing temperature. Three design of solar cells, based on CIGS, were examined to reach the suitable solar cell with higher efficiency.

Changes in gamma attenuation behaviour of sol-gel derived CIGS thin film irradiated using Co-60 radioisotope

Copper indium gallium (di) selenide-Cu(In, Ga)Se2 (CIGS) thin films were fabricated on soda-lime silicate glass substrates using a layer-by-layer sol-gel dip-coating method. The irradiation procedure was handled using a certified Co-60 radioisotope at two different absorbed dose levels (at 0,03 and 0,05 Gray (Gy)) to examine the enhancements of optical and electrical properties of the CIGS thin films. Cs-137 (with 0,662 MeV) and Co-60 (with ∼1,25 MeV) radioisotopes were used to evaluate the effect of the absorbed dose on CIGS thin films with different thicknesses by the gamma transmission technique. The irradiated CIGS thin films exhibited an improved optical band gap and electrical resistivity at the optimal layer thickness. This improvement occurs due to the enhancement of crystalline properties in comparison with those of non-irradiated CIGS thin films. The CIGS thin film of ∼300 nm (11 layers) thickness was suitable for comparing changes in the linear attenuation coefficient after the irradiation process at two different absorbed dose levels. In the experiments, the gamma transmission technique was utilized to investigate the gamma attenuation properties of non-irradiated and irradiated CIGS thin films at different thicknesses against Cs-137 (with 0,662 MeV) and Co-60 (with ∼1,25 MeV) gamma radioisotope sources. The irradiation process and the increase of thickness of CIGS thin films caused a higher linear attenuation coefficient, higher absorption and improvement in electrical conductivity. These results demonstrate the suitability of these materials for solar cell applications in aerospace technology, especially for high-altitude flight operations.

Oblique Angle Sputtering of Chalcogenide Thin Absorbing Film

Abstract CuIn 0.8 Ga 0.2 Se 2 (CIGS) is a chalcogenide semiconducting material used as absorbing layer in photovoltaic cell. In the present study, CIGS thin films were deposited on bare soda lime glass substrate by RF magnetron sputtering at various oblique angles. The structural, surface morphological, film surface roughness, optical, and electrical properties of CIGS thin films were studied at various oblique angles. Films were characterised by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Atomic force microscopy (AFM), UV-Vis-NIR spectrophotometer and four probe method. XRD revealed that all the deposited thin films were polycrystalline with preferred peak intensity along (112) plane. The film deposited at 0° (target- substrate parallel) exhibited larger crystallite size (28 nm) with low dislocation density (1.2×10 15 lines m -2 ). The film surface at this angle was more compact and uniform in comparison to the films deposited at other deposition angles. The optical data revealed that the film exhibits more transparency (23%) at higher oblique angle (60°). The optical band gap of developed film was found to be 1.33 eV at 60° while 1.14 eV at 0°. Slanting morphology was observed at higher oblique angle. The electrical resistivity was following an increasing trend with rise in oblique angle.

Band gap grading and photovoltaic performance of solution-processed Cu(In,Ga)S2 thin-film solar cells.

The photophysical properties of CuInxGa1-xS2 (CIGS) thin films, prepared by solution-based coating methods, are investigated to understand the correlation between the optical properties of these films and the electrical characteristics of solar cells fabricated using these films. Photophysical properties, such as the depth-dependent band gap and carrier lifetime, turn out to be at play in determining the energy conversion efficiency of solar cells. A double grading of the band gap in CIGS films enhances solar cell efficiency, even when defect states disturb carrier collection by non-radiative decay. The combinational stacking of different density films leads to improved solar cell performance as well as efficient fabrication because a graded band gap and reduced shunt current increase carrier collection efficiency. The photodynamics of minority-carriers suggests that the suppression of defect states is a primary area of improvement in CIGS thin films prepared by solution-based methods.

Effects of duty cycle on properties of CIGS thin films fabricated by pulse-reverse electrodeposition technique

DC and pulse-reverse electrodeposition mode were employed for the deposition of polycrystalline Cu(In,Ga)Se2 thin films. In comparison with DC electrodeposition mode, films obtained by pulse-reverse electrodeposition were smoother, denser and more uniform with good adhesion. The Ga content in final composition of CIGS thin film was improved in pulse-reverse electrodeposition mode. In addition, pulse-reverse electrodeposited CIGS thin films were more crystalline with chalcopyrite structure. The compact morphology without pores in the deposit was achieved in the pulse-reverse electrodeposited CIGS thin films by varying duty cycle.

The Effects of Selenization Temperature on the Properties of CIGS Thin Film Prepared by Cu-In-Ga-Se Precursors

CIGS thin films were prepared by selenization of Cu-In-Ga-Se precursors, as a new method, the effects of selenization temperature on the properties of CIGS thin films were studied. First, Cu-In-Ga-Se precursors were deposited onto Mo-coated soda lime glass by evaporation and sputtering method. Then, precursors were selenized at various temperatures in N2 atmosphere for 120 min to form CIGS thin films. The degree of reaction and morphology of films as a function of selenization temperature were analyzed. By means of field emission scanning electron microscope (SEM) and X-ray diffraction (XRD), it was found that CIGS thin films selenized at 450°C exhibit chalcopyrite phase with preferred orientation along the (112) plane.

Experimental and theoretical investigations of structural and optical properties of CIGS thin films

Experimental and theoretical studies of the structural and optical properties of Copper Indium Gallium diSelenide thin films have been performed. Thin films of CIGS were deposited on glass substrates by chemical bath deposition. From the XRD results of the films, it is found that the films are of chalcopyrite type structure. The lattice parameter were determined as a = 5.72 A and c = 11.462 A. The optical properties of the thin films were carried out with the help of spectrophotometer. First principles density functional theory calculations of the band structure, density of states and effective masses of electrons and holes of the CIGS crystals have been done by computer simulations. The experimental data and theoretically calculated data have demonstrated good agreement.

Effects of Ga contents on properties of CIGS thin films and solar cells fabricated by co-evaporation technique

This study examined the effects of Ga content in the CIGS absorber layer on the properties of the corresponding thin films and solar cells fabricated using a co-evaporation technique. The grain size of CIGS films decreased with increasing Ga content presumably because Ga diffusion during the 2nd stage of the co-evaporation process is more difficult than In diffusion. The main XRD peaks showed a noticeable shift to higher diffraction angles with increasing Ga content, which was attributed to Ga atoms substituting for In atoms in the chalcopyrite structure. Band gap energy and the net carrier concentration of CIGS films increased with Ga/(In + Ga) ratios. Regarding the solar cell parameters, the short circuit current density ( J SC) decreased linearly with Ga/(In + Ga) ratios due to the lack of absorption in the long-wavelength portion of the spectrum, while the open circuit voltage ( V OC) increase with those. However, V OC values at high Ga/(In + Ga) regions (>0.35) was far below than those extrapolated from the low Ga contents regions, finally resulting in an optimum Ga/(In + Ga) ratio of 0.28 where the solar cell showed the highest efficiency of 15.56% with V OC, J SC and FF of 0.625 V, 35.03 mA cm −2 and 0.71, respectively.

Study of electrical properties of CIGS thin films prepared by multistage processes

In this work, the dispersion mechanisms affecting the electric transport in CuIn 1− x Ga x Se 2 (CIGS) thin films grown by a chemical reaction of the precursor species, which are evaporated sequentially in two and three-stage processes are analyzed. It was found, through conductivity and Hall coefficient measurements carried out as functions of temperature, that the electrical conductivity of the CuIn 1− x Ga x Se 2 films is affected by the transport of free carriers in extended states of the conduction band as well as for variable range hopping transport mechanisms, each one predominating in a different temperature range.

Ion beam assisted deposition of Cu(In,Ga)Se2 films for thin film solar cells

ABSTRACTWe report on a novel ion beam selenization process. The reactive chalcogen component Se and a significant part of the thermal energy needed for CIGS formation is delivered directly into the growing surface by a low energy Se ion beam from a broad beam ion source. This highly controllable technique with respect to ion energy, dose and uniformity and with scale- up capabilities can be used in two ways either for selenization of metallic Cu/(In,Ga) thin film stacks or in co-deposition. In the case of co-deposition the CIGS growth temperature can be reduced to < 400°CBesides the description of the method we present results of Se ion beam analysis and properties of CIGS thin films, produced by the novel selenization process.

Significance of substrate temperature on the properties of flash evaporated CuIn 0.75Ga 0.25Se 2 thin films

The substrate temperature is an important parameter in thin film deposition regardless of the deposition technique being used to deposit thin films. In this paper the effects of the substrate temperature on the properties of CuIn 0.75Ga 0.25Se 2 (CIGS) thin films are reported. Structure, surface morphology and optical properties of CIGS thin films deposited at various substrate temperatures have been investigated using a number of analysis techniques. X-ray diffraction (XRD) analysis at room temperature shows that CIGS films exhibit a strong 〈112〉 preferred orientation. As expected, at higher substrate temperatures the films displayed a higher degree of crystallinity. The 〈112〉 peak was also enhanced and other CIGS peaks appeared simultaneously. These results were supported by experimental work using Raman spectroscopy. The Raman spectra of the as-grown CIGS thin films show only the A 1 mode peak. The intensity of this peak was enhanced at higher deposition temperatures. Scanning electron microscopy (SEM) results revealed very small grains separated by larger voids in films fabricated at room temperature. When the substrate temperature was increased the average grain size also increased together with a reduction in the number and size of the voids. The deposition temperature also had a significant influence on the transmission spectra.