Copper Indium Gallium Diselenide Thin Films Research Articles

Effect of ultrasonic bonding and lamination on electrical performance of copper indium gallium (de)Selenide CIGS thin film photovoltaic solar panel

This paper aims to study the effect of ultrasonic aluminum (Al) bonding and lamination processes on the electrical performance of copper indium gallium (di)selenide (CIGS) thin film photovoltaic (TFPV) solar panels. Ultrasonic Al bonding on the MoSe2 layer of the CIGS TFPV solar panel was performed in three configurations: eight bonds, 16 bonds, and parallel configurations. The lamination process was performed on the Al bonds with MoSe2 layers of the CIGS TFPV solar panel. Ultrasonic bonding and lamination processes significantly affect the electrical performance of CIGS TFPV solar panels. Open circuit voltage, Voc is the least affected electrical characteristic with the application of ultrasonic bonding and lamination processes as compared to short circuit current (Isc), current density (Jsc), maximum power (Pmpp), fill factor (FF), and efficiency. 8-bonds configuration has the highest efficiency, ranging from 11.45% to 13.86% throughout unique connections of I-V measurement, compared to 16-bonds ranging from 7.99% to 10.77%, and parallel configurations, ranging from 9.14% to 11.92%. The notable variations in electrical properties with the processes used to create laminated CIGS TPFV solar panels with ultrasonic Al bonding can be explained by physical examination and lock-in infrared (IR) thermography. The ultrasonic Al bond is best suited to be used as the interconnection mean in the CIGS TFPV solar panel compared to that of conductive adhesive that has been widely applied nowadays.

Simulation of new thin film Zn(O,S)/CIGS solar cell with bandgap grading

Copper-Indium-Gallium-diSelenide (CIGS) thin film solar cell is a promising candidate for energy harvesting because of its high absorption coefficient and low cost compared to silicon-based solar cells. Absorber layer bandgap grading is a suitable method to improve CIGS thin film solar cell performance. Bandgap grading leads to a decrease in the recombination rate at the rear surface, which increases the open circuit voltage. Furthermore, bandgap grading improves the short circuit current due to the enhancement of collection probability. This paper introduces various routes for improving the performance of thin film CIGS solar cells by using bandgap grading. As a first step, both the bandgap energy and the thickness of the CIGS absorber layer of a uniform bandgap profile are optimized to get the best performance. Simulation is performed using SCAPS software and optimization results show that CIGS absorber layer with a bandgap of 1.2 eV and a thickness of 0.7 μm achieves a 22.48% efficiency. Then, bandgap grading with a parabolic distribution of various profiles is investigated and compared. It is found that with a parabolic double bandgap grading profile, which is a combination of front and back grading, an efficiency of up to 24.16% is achieved. This improvement is obtained using a gallium composition ratio of 0.1 for the minimal bandgap at 0.1 μm and 0.13 μm from the back contact and front contact, respectively. This result represents a 7.47% improvement compared to the baseline structure of a CIGS solar cell.

Microstructural investigation of inkjet printed Cu(In,Ga)Se2 thin film solar cell with improved efficiency

Inkjet printed copper indium gallium diselenide (CIGS) thin film solar cell has attracted tremendous attention because of its various technological benefits as a non-vacuum process. Focused efforts in selenization of inkjet printed films to make the process feasible, are desired. In this work, microstructural investigation of inkjet printed precursor film selenized by rapid thermal processing (RTP) is presented. The optimization of selenization time for transforming metal nitrates precursor ink to CIGS thin film is investigated. Based on the results, the growth mechanism to form CIGS from inkjet printed CIG precursor films is proposed. Systematic study on the molybdenum diselenide (MoSe2) phase evolution during the two-step atmospheric pressure selenization process at the CIGS-Mo interface and its effect on device performance are carried out. Non-uniform inter-diffusion of indium (In) and gallium (Ga) during selenization, resulting in double-layered CIGS, one of the major reason limiting the performance of the devices is investigated through XRD, Raman, FESEM, EDS and Mott-Schottky analysis. The significant improvement in device efficiency from 0.4% to 4.2% is achieved due to microstructural improvement in CIGS films. Investigation on the mechanism of microstructural growth with selenization time affecting final device performance is presenting in this work.

Influence of the active leakage current pathway on the potential induced degradation of CIGS thin film solar modules

Copper Indium Gallium Diselenide (CIGS) shows a degradation due to a voltage between the solar cell and the ground potential, known from other solar cell technologies as well. This degradation is named potential induced degradation (PID). At the cell level, PID has been studied in laboratory experiments and can be traced back to sodium diffusion, which is accelerated by the mentioned voltage against ground potential. The applied potential will lead to a leakage current, which can serve as an indicator for PID.The question whether PID of CIGS thin film solar modules also occurs in real PV power plants inevitably arises. To solve this question the degradation behaviour will be analysed by accelerated aging tests. Furthermore, the influence of different leakage current pathways will be shown. The results of this study serve as a basis for modelling the lifetime of CIGS thin-film solar modules taking degradation due to PID into account.

High-Efficiency Cu(In,Ga)Se₂ Thin Film Solar Cells Using ZnS and CdS Buffer Layers.

Most of the existing copper indium gallium diselenide (CIGS) thin film solar cells are based on a cadmium sulfide (CdS) buffer layer fabricated using a chemical bath deposition (CBD) process. However, due to environmental pollution caused by material toxicity and the unique wet process's incompatibility with the vacuum process, many studies are now being actively carried out on nontoxic buffer layers. In this study, to replace CdS buffer layers, zinc sulfide (ZnS) buffer layers with a big band gap and a low optical loss at a short wavelength were fabricated using a magnetron sputtering system. For comparative analysis, this study also fabricated CdS buffer layers using the CBD process. Then, the conversion efficiency of CIGS thin film solar cells deposited with ZnS and CdS thin film as buffer layers was measured. The light conversion efficiency of ZnS buffer layer-based CIGS was measured at 14.44%, while that of the CdS buffer layer-based CIGS was measured at 15.71%. Given that both are higher than the minimum conversion efficiency required for commercialization (10%), ZnS buffer layer-based solar cells could have a competitive edge over the existing CdS buffer layer-based solar cells.

Comprehensive characterization of CIGS absorber layers grown by one-step sputtering process

We have demonstrated that the use of a one-step sputtering process allowed for the fabrication of copper indium gallium diselenide (CIGS) thin films by RF magnetron sputtering without an additional selenization process. The CIGS thin films deposited at different substrate temperatures were synthesized on soda-lime glass (SLG) substrates using a single quaternary CIGS target. The film composition ratios of ([Cu]/[In]+[Ga]), ([Ga]/[In]+[Ga]), and ([Se]/[Cu]+[In]+[Ga]) were almost consistent with those of the sputtering target. X-ray diffraction (XRD) and Raman results showed that the crystallinity of the CIGS thin films was gradually improved as substrate temperatures increased. Transmission electron microscopy (TEM) showed that the films grown at 600 °C have a columnar structure with the grain size of ~100 nm. In addition, for the CIGS films grown at 600 °C, TEM-EDX analysis revealed that the synchronized fluctuation of the Cu and Se signals was observed in the direction of the film depth, while the In and Ga signals were constant. As a result, the CIGS solar cell made using the film showed a degraded cell efficiency of 2.5%, which might be have been caused by not only Cu-rich and Se-poor compositions but the locally unstable composition in the CIGS films fabricated by one-step sputtering.

Environmental assessment of vacuum and non-vacuum techniques for the fabrication of Cu2ZnSnS4 thin film photovoltaic cells

Cu2ZnSnS4 (CZTS) is one of the most promising alternatives for photovoltaic (PV) applications, since it is made from earth abundant and low toxicity materials. To assess the potential of CZTS PV cells in the future global market, it is useful to investigate the sustainability by assessing the possible environmental impacts of large-scale production. Life cycle assessment (LCA) of CZTS absorber layers fabricated by vacuum and non-vacuum deposition techniques has been studied using information from laboratory-scale processes as well as large scale estimations. Copper indium gallium diselenide (CIGS) was selected as a reference vacuum-based process. The paper compares the environmental impacts of the vacuum and non-vacuum processes by considering the three main damage categories of climate change, human health and eco-toxicity using Sima Pro software. The results show that the CZTS films fabricated with both deposition techniques exhibit a significant potential benefit over the CIGS thin films. The toxicity to human health was found to depend critically on the compounds and components selected for preparing the precursors. The energy consumption for processing the CZTS thin films via the non-vacuum deposition technique is considerably less than that required for the other techniques.

Texture Analysis of Flash Evaporated CIGS Thin Films for Photovoltaic Devices

Copper Indium Gallium Diselenide (CIGS) is a chalcogenide composite from I-II-IV group. It is widely used as an absorber layer having absorption coefficient α ∼ 10-5 cm-1 for fabrication of solar modules. In present study CIGS thin films were deposited by flash evaporation technique at different substrate temperature. Thin Films of 200 nm thickness were deposited on soda lime glass at different temperatures viz. Room temperature (RT), 200 °C, 225 °C, 250 °C, 275 °C, and 300 °C. The effect of substrate temperature on texture orientation was investigated. The thin films of two different thickness i.e. 200 nm was annealed at 400 °C in forming gas (N2: H2) atmosphere. The effect of annealing on the texture orientation was studied. The crystallite size of CIGS thin films in as deposited and annealed condition was measured using X-Ray diffraction. It was found that in CIGS thin films texture quality and crystallite size is enhanced by annealing treatment.

Effect of post deposition annealing on the structure, morphology, optical and electrical properties of CuInGaSe2 thin films

Polycrystalline copper indium gallium diselenide (CIGS) thin film is a favourable candidate for solar cell applications. In the present work the effect of post-deposition annealing on the structure, surface morphology, optical and electrical properties are discussed. Initially, gallium rich CIG thin films were deposited by RF magnetron sputtering followed by an indium rich CIG layer and subjected to selenization to realize CIGS stoichiometry. X-ray diffraction (XRD) results revealed the polycrystalline nature of the films with chalcopyrite structure having preferential orientation along <112> direction normal to the substrate. Optical properties of CIGS thin films were studied using UV–vis spectrophotometry and the band gap of CIGS was found to be around 1.15 eV. Hall Effect studies carried out on the CIGS thin films showed a linear dependence of conductivity with post deposition annealing. The elemental composition of the films was quantified using X-ray photoelectron spectroscopy (XPS) and the results are discussed.

Quantitative analyses of photovoltaic CIGS thin films via SIMS depth profiling with elemental ions and MCs+ clusters

Polycrystalline copper–indium–gallium–diselenide (CIGS) is used as an absorber in thin‐film solar cells because of its appropriate band gap and high absorption coefficient for solar radiation. Many research groups have determined the CIGS compositions related to solar cell efficiency. In this work, three different Cu(In,Ga)Se2 thin films were prepared on molybdenum back contacts deposited on soda‐lime glass substrates via a three‐stage evaporation or, alternatively, a two‐step selenized process. Surface analyses via AES, XPS, and SIMS were used to characterize the CIGS thin films and compare their depth profiles. The MCs+ clusters were detected to improve the quantification of major compositions in the CIGS thin films while suppressing the matrix effect in the SIMS depth profiles. The compositional distribution in the MCs+‐SIMS was in good agreement with the AES and XPS depth profiles. The MCs+‐SIMS results proved more quantitatively accurate than those from the elemental SIMS while comparing to ICP‐AES data. Copyright © 2014 John Wiley &amp; Sons, Ltd.

CuIn1−xGaxSe2 thin-film absorber layers for solar photovoltaics fabricated by two-stage pulsed current electrodeposition

Single phase polycrystalline Copper Indium Gallium Diselenide (CIGS) thin-films for solar photovoltaic applications were fabricated by an economical two-stage method of Pulsed Current (PC) electrodeposition. Cu, Ga and Se were first co-deposited onto a Mo foil followed by deposition of In. The as-deposited films were annealed in Argon atmosphere at 550°C for 30min and were further characterized to study their morphology, phase constitution, and optical absorption. The results revealed that the films have a compact morphology and are comprised of a crystalline chalcopyrite single phase CIGS. The bandgap of the CIGS films was found to be 1.27eV from absorption studies. The photoelectrochemical studies revealed the p-type nature of CIGS films with improved photocurrent over that obtained for one-stage PC electrodeposited CIGS thin-films.

Patterning of CIGS thin films induced by rear-side laser ablation of polyimide carrier foil

Laser patterning of thin films is essential for the future development of flexible electronic devices. The damage-free scribing of thermally sensitive thin films such as copper–indium–gallium diselenide (CIGS) that is required for solar module fabrication by integrated interconnections is still challenging. In this study a new approach for non-thermal, damage-free scribing of CIGS films on polyimide foil is proposed and demonstrated. In contrast to the usually used direct laser ablation of the thin-film stack, laser ablation of the polyimide carrier foil at laser fluences higher than 3 J/cm2 is utilized to achieve CIGS film delamination and thus the patterning of the thin film. The edges of the patterned CIGS films do not show typical laser-ablation-induced modifications like melting, debris contamination, or crack formation. The mechanism of the thin-film removal is of non-thermal origin and is probably due to stress formation at the CIGS/Mo interface resulting from secondary processes of polyimide laser ablation like shock-wave formation or local sample deformation.

Picosecond Laser Induced Selective Removal of Functional Layers on CIGS Thin Film Solar Cells

Abstract Picosecond laser pulses provide a controlled laser based removal used for micro structuring of functional layers, such as copper-indium-gallium-diselenide (CIGS), due to a reduced thermal penetration depth, compared to nanosecond pulses. It is shown that with 7 ps pulse width at a wavelength of 532 nm the P2 and P3 processing of thin film solar cells on glass substrates and flexible polyimide substrates is possible. A Gaussian as well as a top-hat energy distribution were utilized for the experiments. With adjusted laser and processing parameters they allow for the fabrication of precise isolation trenches (width

Synthesis of CIGS thin film by solvothermal route

This study presents the synthesis of copper indium gallium (di)selenide (CIGS) films by a solvothermal method. Four factors in CIGS synthesis are considered: In/Ga ratios, hydrogen contents during thermal annealing, thermal annealing temperatures, and annealing times. Experimental results show that the optimal parameters for CIGS film synthesis are the following: proportion of Cu:In:Ga:Se = 1:0.7:0.3:2; hydrogen content during thermal annealing, 5%; thermal annealing temperature, 600 °C; and annealing time, 100 min. The largest crystal grain size of a CIGS film synthesized using these optimal parameters is about 100 nm. The crystal grain size is also found to be inversely proportional to sheet resistance. This relationship holds true because a smaller crystal indicates more grain boundaries and defects. Thus, an electron encounters more barriers in the transmission process, and electric conductivity decreases.

Fabrication of CIGS nanoparticle-ink using ball milling technology for applied in CIGS thin films solar cell

Abstract A copper–indium–gallium–diselenide layer was formed from the binary-alloy nanoparticles of In 2 Se 3 , Ga 2 Se 3 , and CuSe. Copper–indium–gallium–diselenide thin films were fabricated using the precursor nanoparticle-ink based on non-vacuum technology. The ink was fabricated by a ball milling procedure and the size of agglomerated copper–indium–gallium–diselenide powder after milling was less than 100 nm. Crystallographic, morphological, stoichiometric, and photovoltaic properties of the films were characterized by sintering the precursor copper–indium–gallium–diselenide samples with different holding times in a non-vacuum environment without selenization. Analytical results indicate that the copper–indium–gallium–diselenide absorption layer prepared with a holding time of 7.5 min has a chalcopyrite structure and favorable compositions. The obtained compositions of the sample are Cu 0.976 In 0.811 Ga 0.277 Se 1.935 , and the ratios of Ga/(In + Ga) and Cu/(In + Ga) are 0.254 and 0.896, respectively. The photovoltaic properties of this sample are E g of 1.185 eV, V oc of 0.643 V, N ds of 1.3 × 10 15 cm − 3 , and Ga of 0.277 mol, respectively.

Preparation of CIGS Thin Films by Electrodeposition Method Using Ethanol as a Solvent

We prepared copper indium gallium diselenide (CIGS) thin films by potentiostatic electrodeposition in an ethanol solution. The thin films were characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and UV-visible-near infrared (UV-VIS-NIR) spectrophotometry to determine their morphology, composition, crystal structure, and absorption properties. The results show that the chalcopyrite structured CuIn0.7Ga0.3Se2 thin films can be obtained by annealing the electrodeposited films at-1.6 V (vs SCE) at 450 °C. The obtained thin film has uniform morphology, good crystallinity, and a bandgap of about 1.17 eV. We found that ethanol as a solvent can effectively avoid the hydrogen evolution phenomenon, which often occurs in aqueous solution and reduces the deposition potential limitation.

One-pot electrodeposition, characterization and photoactivity of stoichiometric copper indium gallium diselenide (CIGS) thin films for solar cells

Herein we report the one-pot electrodeposition of copper indium gallium diselenide, CuIn(1-x)Ga(x)Se(2) (CIGS), thin films as the p-type semiconductor in an ionic liquid medium consisting of choline chloride/urea eutectic mixture known as Reline. The thin films were characterized by scanning electron microscopy with energy dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman microspectroscopy, and UV-visible spectroscopy. Based on the results of the characterizations, the electrochemical bath recipe was optimized to obtain stoichiometric CIGS films with x between 0.2 and 0.4. The chemical activity and photoreactivity of the optimized CIGS films were found to be uniform using scanning electrochemical microscopy and scanning photoelectrochemical microscopy. Low-cost stoichiometric CIGS thin films in one-pot were successfully fabricated.