Copper Indium Gallium Selenide Cells Research Articles

Influence of photovoltaic cell technologies and elevated temperature on photovoltaic system performance

This work deploys a configured hypothetical 6-kWp capacity PV system, with mounted rooftop panels, to examine the performance of a PV system, corresponding to different (a) PV cell technologies; (b) ambient temperatures. The first (crystalline silicon (c-Si)) and second (copper indium gallium selenide (CIGS)) generations of PV cells have been chosen for this study. A range of ambient temperatures, −10 °C to 50 °C, at an interval of 5 °C, will be used to investigate the influence of temperature on PV system performance, using the chosen PV cells. A PV design and simulation software, PVsyst, was deployed based on optimisation considerations. It was observed from the report that: the CIGS PV cell produced the highest energy at standard tests and conditions (STC) and elevated temperature; the Si mono and polycrystalline yielded the same amount of energy; the CIGS and Si monocrystalline cells PV have the highest and lowest PR, respectively.

Investigation on the electrical performance of a curved PV roof integrated with CIGS cells for traditional Chinese houses

Inspired by traditional Chinese architecture, a curved PV roof integrated with copper indium gallium selenide (CIGS) cells is designed, which not only manifests Chinese aesthetic elements but also could generate electricity. Considering solar radiation distribution on curved PV cells different from that on traditional flat cells, this paper builds a radiation distribution model to calculate the radiation on the curved surface and an electrical model based on 5-parameter model to predict the power output of PV cells with different connections (independent output; in parallel; in series). An experimental rig was built, and the theoretical model was validated. Results showed that the CIGS cells on the west side of the curved surface performed better in electricity generation than the CIGS cells on the east side did; the CIGS cells in parallel generated more power than the cells in series did. The annual performance prediction shows that CIGS cells on the west side generate 155.18 kWh, which is 21.49% more than on the east side; CIGS cells in parallel generate 275.96 kWh, which is 12.56% more than the cells in series; The electrical generation of the curved PV roof is 7.41% less than the flat roof does. Parametric analysis is also conducted.

Modeling of GaAsxP1-x/CIGS tandem solar cells under stress conditions

In this paper, we design a four-terminal gallium arsenide phosphide (GaAsxP1-x)/copper indium gallium selenide (CIGS) tandem solar cell by the analytical model. We used the experimental data for GaAsxP1-x and CIGS cells to validate this model. In this work, we achieved a 30% efficiency for the optimum GaAsxP1-x/CIGS tandem solar cell. Our proposed model determines the optimized bandgap of GaAsxP1-x as the top cell is within the range from 1.79 eV to 1.95 eV (0.57<x < 0.7). Next, we investigate the degradation in the performance parameters of our tandem solar cell, considering the aging time under stress conditions. In this condition, the defect density increases exponentially over time, and the depletion width decreases with time. The results show that for an optimal GaAs0.6P0.4/CIGS tandem structure, after 277 h (t = 106 s), efficiency decreases by 35.6% under stress conditions. Improving the stability of GaAs0.6P0.4/CIGS tandem solar cell makes this configuration a greater potential to be used in space applications.

Hot-spot generation model using electrical and thermal equivalent circuits for a copper indium gallium selenide photovoltaic module

Hot-spot generation is critical to the reliability and performance of copper indium gallium selenide (CIGS) solar cells; however, its occurrence mechanism has not been fully elucidated. We conducted a partial shade stress test on three large-area CIGS modules (156 cm × 62.6 cm in size, with 102 cells) connected in series. Partial shade stress can cause irreversible and unpredictable damage to the modules, and we confirmed the generation of hot spots on the shaded cells via infrared imaging. To emulate numerically the internal electrical and thermal changes in the shaded cells, we present electrical and thermal equivalent circuits based on the material properties and layered structure of the CIGS cells and modules. Furthermore, we propose a hot-spot generation model describing the irreversible damage to CIGS cells via shunt resistance degradation because the dissipated electrical power exceeds the threshold power (Pth). The current–voltage characteristics simulated by the presented method are congruent with those measured under partial shade conditions. Partial shade induces high electrical power consumption in the shaded cells, up to ~34 mW/cm2 at a 5% shade ratio, ~1,500 times higher than that in the unshaded cells. The shunt resistance is degraded to ~18.5 Ω/mm2 (only ~0.1% of the initial normal value), and the Pth-value is estimated to be ~2.4 mW/cm2 at the center of the hot-spot cells. The presented method and Pth-parameter can be used to evaluate durability with respect to the effects of partial shade stress for CIGS and various other thin-film photovoltaic cells and modules.

Comparative study of the copper indium gallium selenide (CIGS) solar cell with other solar technologies

A comparative study among photovoltaic technologies: (1) comparison of CIGS technology with others: theoretical, experimental and simulations; (2) optical simulations for CIGS, c-Si and perovskite cells; (3) study of the impact of the gallium and indium on the absorption.

N-Functionalized Graphene Quantum Dots with Ultrahigh Quantum Yield and Large Stokes Shift: Efficient Downconverters for CIGS Solar Cells

Copper indium gallium selenide (CIGS) is the most promising thin film solar cell technology. However, its high performance is hampered by its poor short-wavelength response. The short-wavelength response can be enhanced via photon downconversion using quantum dots. Unfortunately, most graphene quantum dots (GQDs) are not suitable as downconverters in CIGS cells owing to their low photoluminescence quantum yield (PL QY) and/or low Stokes shift. Herein, an ultrahigh PL QY (99%) and a large Stokes shift (98 nm) are achieved for N-doped GQDs via a novel method. The performance of a CIGS solar cell is enhanced via photon downconversion and the light-trapping effect using the NGQDs. The effectiveness of the NQGDs is manifested in a conversion efficiency (η) of 15.31%. In addition, improvements in the short-circuit current density from 30.69 mA/cm2 to 31.77 mA/cm2 and fill factor from 71.25% to 73.09% are observed. The n and J0 values are decreased by insertion of NGQDs, indicating a reduction in the recombinati...

Impact of heat‐light soaking on potassium fluoride treated CIGS solar cells with CdS buffer layer

AbstractIn this study, the effects of light‐soaking (LS), heat‐soaking (HS), and combined LS and HS, that is, heat‐light soaking (HLS) on potassium fluoride (KF)‐treated and KF‐free copper indium gallium selenide (CIGS) solar cells with CBD‐CdS buffer layer were investigated. LS and HS did not change the basic solar cell parameters of CIGS solar cells when they were performed separately. In contrast, HLS improved cell efficiency with increased open‐circuit‐voltage for KF‐treated CIGS solar cells, whereas it reduced cell performance for KF‐free CIGS cells. Capacitance‐voltage measurements confirmed a significantly increased carrier concentration in KF‐treated CIGS solar cells, as compared to KF‐free cells by HLS. X‐ray photoelectron spectroscopy measurement revealed that the HLS did not change the atomic concentration of Cd, S, and O in CBD‐CdS buffer layer. However, the concentration of Na atoms slightly increased at the CIGS surface region, as confirmed from SIMS measurement. It implies a possible reason for increased carrier concentration in KF‐treated CIGS solar cells after HLS. Temperature‐dependent current‐voltage measurements suggests that HLS modify a K‐containing new layer and affects cell performance.

Full Sputtering Deposition of Thin Film Solar Cells: A Way of Achieving High Efficiency Sustainable Tandem Cells?

In the first part of this paper, we will show that a sputtering-based fabrication process exhibiting a low environmental footprint has been developed for the fabrication of copper indium gallium selenide (CIGS) absorbing material. Its originality lies in using room temperature sputtering in a pulsed—direct current mode of a single quaternary target followed by a post-anneal. At any stage of the process, selenium or sulfur atmosphere is used. Inert gas is used, respectively argon and a forming gas, for the deposition and annealing step, respectively. CIGS cells have been fabricated using such an absorbing layer. They exhibit an efficiency close to 12%. A tandem cell approach, using a thin film technology in conjunction with the well-established Si technology, is a promising technique, achieving cells with 30%, and higher, efficiency. Such cells are awaited, jointly with a stronger implementation of low environmental footprint technologies, as a vision for 2030. In the first section, sputtering technique has shown its ability to be developed in such a way achieving an environmentally friendly process that can be moreover compatible to be co-integrated with, for example, Si technology. In a second section, we will present a prospective discussion on the materials that can be applied to produce a sustainable approach for such a tandem cell configuration.

Visualizing the performance loss of solar cells by IR thermography — an evaluation study on CIGS with artificially induced defects

AbstractLocal electric defects may result in considerable performance losses in solar cells. Infrared (IR) thermography is one important tool to detect these defects on photovoltaic modules. Qualitative interpretation of IR images has been carried out successfully, but quantitative interpretation has been hampered by the lack of “calibration” defects. The aims of this study are to (i) establish methods to induce well‐defined electric defects in thin‐film solar cells serving as “calibration” defects and to (ii) assess the accuracy of IR imaging methods by using these artificially induced defects. This approach paves the way for improving quality control methods based on imaging in photovoltaic. We created ohmic defects (“shunts”) by using a focused ion beam and weak diodes (“interface shunts”) by applying a femto‐second laser at rather low power on copper indium gallium selenide cells. The defects can be induced precisely and reproducibly, and the severity of the defects on the electrical performance can be well adjusted by focused ion beam/laser parameters. The successive assessment of the IR measurement (ILIT‐Voc) revealed that this method can predict the losses in Pmpp (maximal power extractable) with a mean error of below 10%. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Ecotoxicological assessment of solar cell leachates: Copper indium gallium selenide (CIGS) cells show higher activity than organic photovoltaic (OPV) cells

Despite the increasing use of photovoltaics their potential environmental risks are poorly understood. Here, we compared ecotoxicological effects of two thin-film photovoltaics: established copper indium gallium selenide (CIGS) and organic photovoltaic (OPV) cells. Leachates were produced by exposing photovoltaics to UV light, physical damage, and exposure to environmentally relevant model waters, representing mesotrophic lake water, acidic rain, and seawater. CIGS cell leachates contained 583μgL−1 molybdenum at lake water, whereas at acidic rain and seawater conditions, iron, copper, zinc, molybdenum, cadmium, silver, and tin were present up to 7219μgL−1. From OPV, copper (14μgL−1), zinc (87μgL−1) and silver (78μgL−1) leached. Zebrafish embryos were exposed until 120h post-fertilization to these extracts. CIGS leachates produced under acidic rain, as well as CIGS and OPV leachates produced under seawater conditions resulted in a marked hatching delay and increase in heart edema. Depending on model water and solar cell, transcriptional alterations occurred in genes involved in oxidative stress (cat), hormonal activity (vtg1, ar), metallothionein (mt2), ER stress (bip, chop), and apoptosis (casp9). The effects were dependent on the concentrations of cationic metals in leachates. Addition of ethylenediaminetetraacetic acid protected zebrafish embryos from morphological and molecular effects. Our study suggests that metals leaching from damaged CIGS cells, may pose a potential environmental risk.

A Novel Solar Simulator Based on a Supercontinuum Laser for Solar Cell Device and Materials Characterization

The design, operation, and application of a novel solar simulator based on a high-power supercontinuum fiber laser are described. The simulator features a multisun irradiance with continuous spectral coverage from the visible to the infrared. By use of a prism-based spectral shaper, the simulator can be matched to any desired spectral profile, including the ASTM G-173-03 air-mass 1.5 reference spectrum. The simulator was used to measure the efficiency of gallium arsenide (GaAs), crystalline silicon (Si), amorphous Si, and copper-indium-gallium-selenide (CIGS) thin-film solar cells, showing agreement with independent measurements. The pulsed temporal characteristic of the simulator was studied and would appear to have a negligible influence on measured cell efficiency. The simulator light was focused to a spot of approximately 8 μm in diameter and used to create micrometer-scale spatial maps of full spectrum optical-beam-induced current. Microscopic details such as grid lines, damage spots, and material variations were selectively excited and resolved on GaAs and CIGS cells. The spectral shaping capabilities were used to create output spectra appropriate for selectively light-biasing multijunction cell layers. The simulator was used to create variable blue-rich and red-rich spectra that were applied to a GaInP/GaAs tandem solar cell to illustrate the current-limiting behavior.

Thin-Film Photovoltaic Cells: Long-Term Metal(loid) Leaching at Their End-of-Life

The photovoltaic effect of thin-film copper indium gallium selenide cells (CIGS) is conferred by the latter elements. Organic photovoltaic cells (OPV), relying on organic light-absorbing molecules, also contain a variety of metals (e.g., Zn, Al, In, Sn, Ag). The environmental impact of such technologies is largely unknown, in particular when the physical integrity deteriorates upon end-of-life, possibly facilitating cell constituent leaching. This study analyzed long-term inorganic leaching from damaged OPV and CIGS into different model waters. Leachate concentrations were put into perspective by calculating the predicted environmental concentrations (PEC) for several scenarios. Roof-top acidic rain runoff from CIGS was found to be the predominant emission source for metals and metalloids, with Cd released to such extents that PEC (173.4 μg Cd L(-1)) would considerably exceed acute toxicity concentrations for Daphnia magna . Other PEC for CIGS (9.9 mg Mo L(-1) and 9.4 μg Se L(-1)) were in the range of teratogenic effects. In contrast, OPV released little metals with calculated PEC being below even conservative drinking water guidelines. Time-resolved single-particle ICP-MS indicated that some metals (Zn, Mo, Ag) were in nanoparticulate form, raising nanotoxicity concerns. Leaching kinetics called for revision of existing standardized (accelerated) leaching protocols because long-term release was most relevant.

Experimental characterization and simulation of water vapor diffusion through various encapsulants used in PV modules

Water vapor ingress significantly impacts the performance and the long-term reliability of copper indium gallium selenide photovoltaic modules. A cost effective packaging method that can protect photovoltaic modules from the operating environment is critical to their widespread commercialization. Due to the sensitivity of both the copper indium gallium selenide cells and the electrodes to water vapor, they need an encapsulant with low water vapor permeation as well as side sealing materials, resulting in a high cost of manufacturing. Hence, a packaging strategy without sealing materials is proposed with new encapsulant materials. In this study, the overall amount of permeated water vapor through ionomer and polyvinyl butyral encapsulants was investigated and compared with widely used encapsulants such as ethylene vinyl acetate. The diffusion and solubility coefficients were calculated from the experimentally determined water vapor transmission rate in both transient and steady state transport regimes. To understand the permeation mechanism of water vapor through the encapsulant, the temperature dependence of the diffusion and solubility coefficients was investigated. Based on experimentally determined permeation properties, the amount of water vapor absorption and the ingress speed into the PV module under a continuously varying environment were investigated. Ethylene vinyl acetate shows its excellence among encapsulants, when simply considering ingress speed of water vapor (slower permeation), while ionomer dominantly outperforms other materials, when focusing on the total amount of water absorption (less permeation).

Atomic layer deposition for photovoltaics: applications and prospects for solar cell manufacturing

Atomic layer deposition (ALD) is a vapour-phase deposition technique capable of depositing high quality, uniform and conformal thin films at relatively low temperatures. These outstanding properties can be employed to face processing challenges for various types of next-generation solar cells; hence, ALD for photovoltaics (PV) has attracted great interest in academic and industrial research in recent years. In this review, the recent progress of ALD layers applied to various solar cell concepts and their future prospects are discussed. Crystalline silicon (c-Si), copper indium gallium selenide (CIGS) and dye-sensitized solar cells (DSSCs) benefit from the application of ALD surface passivation layers, buffer layers and barrier layers, respectively. ALD films are also excellent moisture permeation barriers that have been successfully used to encapsulate flexible CIGS and organic photovoltaic (OPV) cells. Furthermore, some emerging applications of the ALD method in solar cell research are reviewed. The potential of ALD for solar cells manufacturing is discussed, and the current status of high-throughput ALD equipment development is presented. ALD is on the verge of being introduced in the PV industry and it is expected that it will be part of the standard solar cell manufacturing equipment in the near future.

Copper–indium–gallium–selenide (CIGS) solar cells with localized back contacts for achieving high performance

Thin-film, polycrystalline, CIGS solar cells with localized and whole back contacts were modeled and simulated in two dimensions (2D) in order to investigate their potential for achieving high performance. The simulation results show that the short-circuit current density (Jsc) of the CIGS cells with localized back contacts increases with a decreasing contacted area due to the decreased cumulative surface recombination rate at the back side of the CIGS layer. The conversion efficiency (η) of these thin-film, CIGS cells can be increased by 15% relatively compared to CIGS cells with traditional whole back contacts if the surface-recombination velocity of the electrons and the holes (sn/p) between two adjacent fingers of the back contact is zero and the density of the acceptor defect states (NtA) inside the CIGS layer is low (NtA<1013cm−3). The polycrystalline properties of the CIGS were modeled by setting vertical grain boundaries (GBs) within the CIGS absorbent layer. The simulation results show that a valence-band offset (VBO) above 0.2eV at the GBs increases the Jsc, but it also significantly reduces the fill factor (FF) of the CIGS cells with localized back contacts. The results show that the efficiency of the CIGS cells with localized back contacts can be increased by 7% relatively if the density of the acceptor defect states at the GBs (NtA,GB) equals 1017cm−3. In contrast, the efficiency of the CIGS cells with localized back contacts can be increased by only 1% relatively at the same NtA,GB if the VBO is 0.5eV.

SSTE-4 Program Advanced Photovoltaic Cell Technologies: Ground Chamber Test Results

Plasma ground-testing results, obtained at the John H. Glenn Research Center National Plasma Interaction Facility, are presented for a number of thin-film photovoltaic cells. The cells represent a mix of promising new technologies identified by the Air Force Research Laboratory under the space science technology experiment (SSTE-4) Program. The current ground-testing efforts are aimed at characterizing both the performance and survivability of thin-film technologies in the harsh Low Earth Orbit space environment where they are intended to be flown. Measurements of parasitic currents and arc threshold voltages were performed <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">situ</i> under strictly controlled charging conditions for both amorphous silicon (a-Si) and copper indium gallium selenide cells. Surface flashing on the large-area a-Si cells revealed that microdischarges in the dielectric surface do not appear to cause any apparent degradation to the cells. Catastrophic arc testing between adjacent cells resulted in no sustained arcs. Similar catastrophic arc tests between adjacent strings resulted in self-extinguished nonsustained arc extensions on time scales of approximately 100 mus in length. All cell efficiency measurements were performed in the Solar Cell Calibration Laboratory prior to plasma testing and then once again after the completion of the plasma tests.