Copper Indium Gallium Selenium Research Articles

Current challenges and future prospects for a highly efficient (>20%) kesterite CZTS solar cell: A review

CZTS has kesterite structure and the composition's formula is Cu2ZnSn(S/Se)4. The efficiency of CZTS-Se (CopperZincTin-Sulphur-Selenium) solar cell, ∼12.6%, is much lower than the efficiency of CIGS (CopperIndiumGalliumSelenium) solar cell, ∼22.6%. But the CZTS-Se may be the counterpart of the CIGS and the efficiency may be increased up to 32.2% as theoretically predicted by the Shockley-Queisser (SQ) limit. In solar cell technology, it has been depicted that the efficiency of the solar are affected by the two parameters: (i) variation of the solar insolation and (ii) quality of the materials. Besides this, the narrow phase stability of quaternary phases, unfavorable band alignments, mid-gap states and band tails are main reasons of deficit in the efficiency of kesterite due to the coexistence of the secondary and ternary phases, carrier recombination at the interfaces, defects and series resistances. As a result, the kesterite solar cell has the fluctuated open circuit voltage and the loss of energy. In addition to this, the champion CZTS-Se solar cell is not so environmental friendly because Se is the toxic and the rare earth element. This review provides the vital approaches by discussing the proper materials processing and the appropriate solution to enhance the efficiency of kesterite (CZTS, CZTSe and CZTS/Se) solar cells. Due to the large area quality, high absorption and low-cost materials of the kesterite, it may be used directly in harvesting the solar energy. We have also discussed how to reduce the recombination of the electron-hole pairs by using the interfacial layer so that the efficiency of the kesterite solar cells can be improved.

Effects of Bottom Layer Sputtering Pressures and Annealing Temperatures on the Microstructures, Electrical and Optical Properties of Mo Bilayer Films Deposited by RF/DC Magnetron Sputtering

Most of the molybdenum (Mo) bilayer films are deposited by direct current (DC) magnetron sputtering at the bottom and the top layer (DC/DC). However, the deposition of Mo bilayer film by radio frequency (RF) Mo bottom layer and DC Mo top layer magnetron sputtering has been less studied by researchers. In this paper, the bottom layer of Mo bilayer film was deposited by RF magnetron sputtering to maintain its good adhesion and high reflectance, and the top layer was deposited by DC magnetron sputtering to obtain good conductivity (RF/DC). Generally, the bottom layer sputtering pressure is relatively random, in this paper, the effects of the bottom layer RF sputtering pressures on the microstructures and properties of Mo bilayer films were first studied in detail. Next, in order to further improve their properties, the as-prepared Mo bilayer films at 0.4 Pa bottom layer RF sputtering pressure were annealed at different temperatures and then investigated. Specifically, Mo bilayer films were deposited on soda-lime glass substrates by RF/DC magnetron sputtering at different bottom layer RF sputtering pressures in the range of 0.4–1.2 Pa, the powers of bottom layer RF sputtering and top layer DC sputtering were 120 W and 100 W, respectively. Then, Mo bilayer films, prepared at a bottom layer sputtering pressure of 0.4 Pa and top layer sputtering pressure of 0.3 Pa, were annealed for 30 min at various temperatures in the range of 100–400 °C. The effects of bottom layer sputtering pressures and the annealing temperatures on the microstructures, electrical and optical properties of Mo bilayer films were clarified by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic-force microscopy (AFM), and ultraviolet (UV)-visible spectra, respectively. It is shown that with decreasing bottom layer sputtering pressure from 1.2 to 0.4 Pa and increasing annealing temperature from 100 to 400 °C, the crystallinity, electrical and optical properties of Mo bilayer films were improved correspondingly. The optimized Mo bilayer film was prepared at the top layer sputtering pressure of 0.3 Pa, the bottom layer sputtering pressure of 0.4 Pa and the annealing temperature of 400 °C. The extremely low resistivity of 0.92 × 10−5 Ω.cm was obtained. The photo-conversion efficiency of copper indium gallium selenium (CIGS) solar cell with the optimized Mo bilayer film as electrode was up to as high as 13.5%.

Effects of Heating Mode and Temperature on the Microstructures, Electrical and Optical Properties of Molybdenum Thin Films.

In this paper, molybdenum (Mo) thin films are deposited on soda-lime glass (SLG) substrates by direct current magnetron sputtering and heated in three different modes at different temperatures, including substrate heating, annealing treatment, and both substrate heating and annealing treatment. The effects of heating temperature and heating mode on the structures, morphology, optical and electrical properties of Mo thin films were systematically investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), atomic force microscope (AFM) and UV-visible spectrophotometer (UV-vis spectra). It is shown that as the substrate and annealing temperature increase, the crystallinity of Mo thin films is improved, and the grain sizes become bigger. Especially in the mode of both substrate heating and annealing treatment at higher temperature, the obtained Mo thin films show higher crystallinity and conductivity. Moreover, with the increase of substrate and annealing temperature in different heating modes, both the surface compactness of Mo films and the optical reflectance increase correspondingly. Furthermore, the Mo film, prepared at the substrate heating temperature of 400 °C and annealed at 400 °C, showed excellent comprehensive performance, and the resistivity is as low as 1.36 × 10−5 Ω·cm. Using this optimized Mo thin film as an electrode, copper indium gallium selenium (CIGS) solar cells have a maximum photo-conversion efficiency of 12.8%.

Structural, electronic and optical properties for chalcopyrite semiconducting materials: ab-initio computational study

Investigation of the physical properties of chalcopyrite materials using ab-initio methods have been carried out to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. The Density Functional Theory calculations have been performed using Wien2k computational package by employing the full-potential linearized augmented plane wave method. Structural and electronic properties of chalcopyrite semiconducting material Copper–Indium–Gallium–Selenium i.e. CuIn1-xGaxSe2 have been investigated using local density approximation for the exchange-correlation potential. The electronic structures and linear optical properties have been studied using both the semi-local Becke-Johnson potential and its modified form i.e. mBJ and TB-mBJ. Computational results are in good agreement with those acquired experimentally. The viability of alloys in realization of ultra-thin-film based (CIGS) solar cells with high performance has been proposed after simulation and analysis study using one of solar cell simulation tools. The studied material exhibits capability to become a promising candidate for fabrication of optoelectronic and photovoltaic devices.

Theoretical simulation of performances in CIGS thin-film solar cells with cadmium-free buffer layer**Project supported by the NSF of Jiangsu Province (No. BK20131420), the Postgraduate Innovation Project of Jiangsu Province (No. KYLX15_0926), and the NJFU Outstanding Young Scholars Funding.

Copper indium gallium selenium (CIGS) thin film solar cells have become one of the hottest topics in solar energy due to their high photoelectric transformation efficiency. To real applications, CIGS thin film is covered by the buffer layer and absorption layer. Traditionally, cadmium sulfide (CdS) is inserted into the middle of the window layer (ZnO) and absorption layer (CIGS) as a buffer layer. However, the application of the GIGS/CdS thin film solar cells has been limited because of the environmental pollution resulting from the toxic cadmium atom. Although zinc sulfide (ZnS) has been proposed to be one of the candidates, the performance of such battery cells has not been investigated. Here, in this paper, we systematically study the possibility of using zinc sulfide (ZnS) as a buffer layer. By including the effects of thickness, concentration of a buffer layer, intrinsic layer and the absorbing layer, we find that photoelectric transformation efficiency of ZnO/ZnS(n)/CIGS(i)/CIGS(p) solar cell is about 17.22%, which is qualified as a commercial solar cell. Moreover, we also find that the open-circuit voltage is ∼0.60 V, the short-circuit current is ∼36.99 mA/cm2 and the filled factor is ∼77.44%. Therefore, our results suggest that zinc sulfide may be the potential candidate of CdS as a buffer layer.

Temperature Effect of Electrical Properties of Cigs Solar Cell

In this paper we are interested in studying the copper–indium–gallium–selenium (CIGS) solar cells sandwiched between cadmium sulfide (CdS) and ZnO as buffer layers, and Molybdenum (Mo). Thus, we report our simulation results using the capacitance simulator (SCAPS) in terms of layer thickness, absorber layer band gap and operating temperature to find out the optimum choice. An efficiency of 20.61% (with Voc of 635.2mV, Jsc of 44.08 mA/cm2 and fill factor of 0.73) has been achieved with CdS used as buffer layer as the reference case. It is also found that the high efficiency CIGS cells with the low temperature were a very high efficiency conversion. Keywords : Thin film solar cells,SCAPS, CIGS, temperature, effiency energetic.

Thin-film metallization of CuInGaSe2 nanoparticles by supersonic kinetic spraying

High-speed spraying quickly deposits dry, solid particles at atmospheric pressure, without the use of binders, across large coating areas. We experimentally deposited Al2O3 and copper–indium–gallium–selenium (CIGS) nanoparticles on Al2O3 and molybdenum substrates and numerically replicated the results to elucidate the details of the deposition mechanisms. Thin films formed from layers of sprayed-particle impacts. Both single- and multiple-particle impacts are simulated and increases in pressure, temperature and von Mises stress are reported. Both experimentally and numerically, micron-sized particles are pulverized into flattened layers of nano-sized particle fragments. Characterizing the impact physics (particle collapse speed, energy exchange, and substrate damage) helps identify the optimum operating envelope for particle speeds less than 200m/s that maximizes thin-film growth rates and minimizes substrate damage.

Photoelectrochemistry of Cu(In,Ga)Se2 thin-films fabricated by sequential pulsed electrodeposition

A novel approach for the fabrication of compact stoichiometric copper indium gallium selenium (CIGS) thin-films is reported. It uses a solution of CuCl2, GaCl3 and H2SeO3, pH adjusted with HCl with LiCl as additive employing a high purity graphite plate anode and Mo sputtered glass cathode during a simplified sequential pulsed current electrodeposition which avoids impurities from the use of a reference electrode during deposition and a separate selenization step. A Cu-Ga-Se film is optimally deposited by optimizing the deposition voltage, followed by deposition of In from InCl3 solution, and then annealing of the Cu-Ga-Se/In thin-film in an Argon atmosphere at 550 °C. A single phase chalcopyrite CIGS forms with a compact morphology and well-controlled composition of individual elements. The flat-band potential and carrier density of CIGS thin-films are −0.15 V and 2.6 × 1016 cm−3, respectively, as determined by Mott–Schottky studies. The photoelectrochemical performance of CIGS films shows a photocurrent density of −0.8 mA cm−2 at −0.4 V vs. SCE, an eight fold increment compared to our previous reported value. This simplified preparation using pulse plating gives superior quality CIGS films which are promising for application in thin-film solar cells and photoelectrochemical cells.

Fabrication of a Complete Photovoltaic CIGS Device by Electrodeposition

Copper Indium Gallium Selenium (CIGS) films are attractive for photovoltaic applications due to their high optical absorption coefficient. Generation of CIGS films by electrodeposition is particularly appealing due to the relatively low capital cost and the relatively high throughput1-3. Numerous publications address the electrodeposition of CIGS; however, to our knowledge, none reports the fabrication of a complete CIGS photovoltaic cell using electrochemical techniques.In this work we introduce electrochemical processes that enable the fabrication of complete CIGS and CIGSS functional photovoltaic devices, based entirely on electroplating. The electrodeposition of the CIGS or CIGSS absorber layers is based on an electrolyte that is far more dilute than systems that had been traditionally used, and which yields much improved CIGS and CIGSS films4,5. In addition to the absorber layer, electrochemical processes for the electrodeposition of the cadmium sulfide (50 nm), and the pure zinc oxide (100 nm) layer are described. Also the electrodeposition of doped zinc oxide (0.5 µ) (window layer) is discussed. The substrate has been stainless steel coated with electrodeposited metal barrier (Ni, Cr, or Cu), enabling continuous strip plating. An intermediate molybdenum layer, providing improved interface to the absorber layer, increased the efficiency. The final device structure is shown in figure 1.Complete electrodeposited devices were generated and tested exhibiting efficiencies ranging from 2 to 6% with quantum efficiency exceeding 0.6 as shown in figure 2. A comprehensive electrochemical process such as described here, will enable the fabrication of the entire device through a fast wet chemical process, providing effective manufacturing integration and scaling.

Comparative alternative materials assessment to screen toxicity hazards in the life cycle of CIGS thin film photovoltaics

Copper–indium–gallium–selenium–sulfide (CIGS) thin film photovoltaics are increasingly penetrating the market supply for consumer solar panels. Although CIGS is attractive for producing less greenhouse gas emissions than fossil-fuel based energy sources, CIGS manufacturing processes and solar cell devices use hazardous materials that should be carefully considered in evaluating and comparing net environmental benefits of energy products. Through this research, we present a case study on the toxicity hazards associated with alternative materials selection for CIGS manufacturing. We applied two numeric models, The Green Screen for Safer Chemicals™ and the Toxic Potential Indicator. To improve the sensitivity of the model outputs, we developed a novel, life cycle thinking based hazard assessment method that facilitates the projection of hazards throughout material life cycles. Our results show that the least hazardous CIGS solar cell device and manufacturing protocol consist of a titanium substrate, molybdenum metal back electrode, CuInS2 p-type absorber deposited by spray pyrolysis, ZnS buffer deposited by spray ion layer gas reduction, ZnO:Ga transparent conducting oxide (TCO) deposited by sputtering, and the encapsulant polydimethylsiloxane.

CIS and CIGS thin films prepared by magnetron sputtering

Copper indium selenium (CIS) and copper indium gallium selenium (CIGS) thin films were prepared by co-sputtering. The crystal structure, surface morphology and composition ratio were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). It was shown that the chalcopyrite structure CIS thin films were obtained by sputtering CuIn and Se targets and further optimized by changing the substrate or annealing temperature. The chalcopyrite structure, good surface morphology and proper stoichiometric ratio for the CIGS thin films were obtained by sputtering CuIn, CuGa and Se targets, which are solid groundwork to get CIGS solar cells with high efficiency.

Synthesis of CuInGaSe2 nanoparticles by modified polyol route

Chalcopyrite of copper indium gallium selenium (Cu(InxGa1−x)Se2; CIGS) nanoparticles for solar cell materials have been successfully synthesized by a relatively simple and convenient method, i.e., a modified polyol route. The In/Ga ratio in the CIGS nanocrystals can be controlled by varying the In/Ga ratio in the reaction, and the optical properties of the CIGS nanocrystals correspond to those of the bulk materials. The use of reactants, CuCl, InCl3, GaCl3 and Se powders, in a three-neck flask with tetraethylene glycol as a solvent, spherical CIGS nanoparticles with diameter in the range of 40–100nm can be obtained at temperatures in the range of 200–280°C. Incorporation of gallium into the CuInSe2 compound requires a much higher reaction temperature for the formation of the CIGS nanoparticles. The characteristics and average sizes of these nanoparticles are analyzed with sophisticated instruments, such as SEM, TEM, EDS, X-ray diffraction pattern, and XRD.

Hall-effect and resistivity measurements in copper–indium–gallium–selenium–tellurium solid solutions

Hall-effect and resistivity measurements of semiconductor alloys of the type Culn1−yGaySe2(1−x)Te2x have been made over the temperature range 77–300 K. All materials were p-type with mobilities in the range 1 < μ < 10 cm2/V∙s. The observed electrical properties are interpreted in terms of the presence of intrinsic defects arising from dissimilar evaporation of the constituent elements of the materials during melting and annealing stages.