Query: CIGS

title: Flexible CIGS, CdTe and a Si:H based thin film solar cells: A review
abstract: Flexible thin film solar cells such as CIGS, CdTe, and a Si:H have received worldwide attention. Until now, Si solar cells dominate the photovoltaic market. Its production cost is a major concern since Si substrates account for the major cost. One way to reduce the module production cost is to use the low cost flexible substrates. It reduces the installation and transportation charges also, thereby reducing the system price. Apart from metallic foils, plastic films and flexible glass, paper substrates such as cellulose papers, bank notes, security papers and plain white copying papers are also used as substrates for flexible solar cells. In this review, recent developments in flexible CIGS, CdTe and a Si:H solar cells are reported. Progress on various flexible foils, fabrication and stability issues, current challenges and solutions to those challenges of using flexible foils, and industrial scenario are reviewed in detail. Encapsulation issues and solutions related to water vapor transmission rate are discussed.

title: Bimolecular Additives Improve Wide Band Gap Perovskites for Efficient Tandem Solar Cells with CIGS
abstract: Tandem solar cells coupling narrow and wide band gap thin film polycrystalline absorbers are attractive for achieving ultrahigh efficiency with low manufacturing cost. For established narrow band gap CIGS thin film bottom cells, a challenge is to develop highly efficient polycrystalline wide band gap top cells. Here, we demonstrate a 1.68 eV (FA0.65MA0.20Cs0.15)Pb(I0.8Br0.2)3 wide band gap perovskite solar cell with an efficiency of ~20% enabled by using PEAI and Pb(SCN)2 complementary additives in the perovskite precursor. The coupling of PEA+ and SCN provides a synergistic effect that overcomes growth challenges with either additive individually and improves perovskite film quality with enhanced crystallinity, reduced formation of excess PbI2 (in comparison to using Pb(SCN)2 additive alone) lower defect density and energetic disorder, and an improved carrier mobility ~47 cm2 V 1s 1) and lifetime ~2.9 ms) When coupling a semi transparent 1.68 eV perovskite top cell fabricated by this approach with a 1.12 eV CIGS bottom cell, we achieve 25.9% efficient polycrystalline perovskite/CIGS 4 terminal thin film tandem solar cells.

title: Mechanically stacked perovskite/CIGS tandem solar cells with efficiency of 23.9% and reduced oxygen sensitivity
abstract: A perovskite/CIGS tandem configuration is an attractive and viable approach to achieve an ultra high efficiency and cost effective all thin film solar cell. In this work, we developed a semi transparent perovskite solar cell (PSC) with a maximum efficiency of 18.1% at a bandgap of ~1.62 eV. Combining this cell in a mechanically stacked tandem configuration with a 16.5% CIGS cell results in a tandem efficiency of 23.9% We also present a semi transparent high bandgap ~1.75 eV) PSC with a champion efficiency of 16.0% that enables a tandem efficiency of 23.4% Optical simulation predicts that a perovskite/CIGS tandem efficiency of over 30% is feasible with a high bandgap perovskite top cell. The multiple cation perovskite absorbers enabling high tandem efficiencies in this work are found to be remarkably less sensitive towards oxygen exposure compared to the widely used CH3NH3PbI3 (MAPbI3) By combining systematic compositional tuning of perovskite materials and the simultaneous probe of terminal open circuit voltage (Voc) and Photoluminence (PL) of PSCs, it is deduced that an interaction between methylamonnium (MA) cations and oxygen molecules results in an increased surface recombination rate, and this is the main driver for oxygen induced degradation. The extraordinary device performance and stability reported in this work pave the way for ultimately realizing the commercialization of all thin film photovoltaic technology.

title: Semi transparent perovskite solar cells for tandems with silicon and CIGS
abstract: A promising approach for upgrading the performance of an established low bandgap solar technology without adding much cost is to deposit a high bandgap polycrystalline semiconductor on top to make a tandem solar cell. We use a transparent silver nanowire electrode on perovskite solar cells to achieve a semi transparent device. We place the semi transparent cell in a mechanically stacked tandem configuration onto copper indium gallium diselenide (CIGS) and low quality multicrystalline silicon (Si) to achieve solid state polycrystalline tandem solar cells with a net improvement in efficiency over the bottom cell alone. This work paves the way for integrating perovskites into a low cost and high efficiency >25% tandem cell.

title: Progress in thin film CIGS photovoltaics Research and development, manufacturing, and applications
abstract: This review summarizes the current status of Cu(In,Ga)(S,Se)2 (CIGS) thin film solar cell technology with a focus on recent advancements and emerging concepts intended for higher efficiency and novel applications. The recent developments and trends of research in laboratories and industrial achievements communicated within the last years are reviewed, and the major developments linked to alkali post deposition treatment and composition grading in CIGS, surface passivation, buffer, and transparent contact layers are emphasized. Encouraging results have been achieved for CIGS based tandem solar cells and for improvement in low light device performance. Challenges of technology transfer of lab's record high efficiency cells to average industrial production are obvious from the reported efficiency values. One section is dedicated to development and opportunities offered by flexible and lightweight CIGS modules.

title: Spatial control of cocatalysts and elimination of interfacial defects towards efficient and robust CIGS photocathodes for solar water splitting
abstract: Chalcopyrite thin film absorbers such as Cu(In,Ga)Se2 (CIGS) exhibit excellent solar energy conversion efficiency, particularly when coupled with CdS to form an excellent p n junction. To advance CIGS towards an efficient photoelectrochemical (PEC) hydrogen evolution reaction (HER) a protective overlayer (typically TiO2) is needed to prevent the corrosion of CIGS and CdS in the electrolyte, and a HER catalyst (typically Pt) is required to promote the surface reaction. However, it is a great challenge to realize delicate spatial control of the HER catalyst on the surface of the protective overlayer using the traditional deposition method. The charge transport through the CdS/overlayer interface is also of vital importance but is rarely considered. Herein, through a new two step platinization strategy, the dispersion and particle size of Pt nanoparticles are independently controlled to realize high HER catalytic activity. Moreover, defects at the CdS/TiO2 interface are passivated via an ultrathin Al2O3 insertion layer. Consequently, we have obtained a robust CIGS/CdS/Al2O3/TiO2/Pt photocathode for PEC hydrogen evolution, which yields an applied bias photon to current efficiency (ABPE) of 6.6% in neutral electrolyte with a long term stability up to 8 h (4.5% drop) and an unprecedented ABPE of 9.3% in acidic electrolyte that is the highest among chalcopyrite based photocathodes. When paired with a BiVO4 photoanode to form a PEC tandem cell, an unbiased solar to hydrogen conversion efficiency of 1.01% is achieved.

title: ZnO nanowire based CIGS solar cell and its efficiency enhancement by the piezo phototronic effect
abstract: Cu(In,Ga)Se2(CIGS) based heterostructures have been thought to be one of the most prospective thin film solar cells. However, considering cost competitiveness, researchers are still seeking for new methods to improve the power conversion efficiency (PCE) In this work, the ZnO nanowires are first introduced into the CIGS based solar cells to substitute the ZnO film for well developing the piezoelectric effect. Interestingly, the solar cells exhibit very good photovoltaic performances with PCE of 9.83% for rigid device and 5.43% for flexible device, the PCE of which is even larger than that of the corresponding ZnO film CIGS devices. Moreover, by exerting piezo phototronic effect of the ZnO nanowires, the PCE of the rigid device is modulated from 9.83% to 11.40% with vertical pressure increasing from 0 to 2 MPa, and the PCE of the flexible device improves from 4.82% to 5.96% with external strain changing from a 0.74% tensile strain to a 0.74% compressive strain. This study demonstrates that introducing ZnO nanowires as well as the associated piezo phototronic effect provides an ideal approach for improving the performances of CIGS based solar cells.

title: Elucidating the Mechanism of an RbF Post Deposition Treatment in CIGS Thin Film Solar Cells
abstract: We investigate the impact of a rubidium uoride post deposition treatment (RbF PDT) on the material and device properties of Cu(In,Ga)Se2 (CIGS) thin lms and corresponding solar cells. The structure and device properties of CIGS with di erent PDT duration are compared. With longer PDT duration, which equals a higher amount of RbF deposited on the CIGS absorber layer, we observe a clear trade o between increasing open circuit voltage (VOC) and decreasing ll factor (FF An optimum of the PDT duration is found increasing the e ciency by about 0.8% (absolute) compared to the Rb free reference device. We explore the mechanisms behind the increased VOC by various characterization methods and identify them as a combination of increased carrier concentration and reduced recombination rates in the device. Possible origins for these mechanisms are discussed. Furthermore numerical simulations are used to analyze the detrimental e ect of the PDT on the FF We nd that thermally activated alkali migration into the transparent front contact could create acceptor states there, which could explain the observed FF loss.

title: Review on Substrate and Molybdenum Back Contact in CIGS Thin Film Solar Cell
abstract: Copper Indium Gallium Selenide (CIGS based solar cells have become one of the most promising candidates among the thin film technologies for solar power generation. The current record efficiency of CIGS has reached 22.6% which is comparable to the crystalline silicon (c Si based solar cells. However, material properties and efficiency on small area devices are crucial aspects to be considered before manufacturing into large scale. The process for each layer of the CIGS solar cells, including the type of substrate used and deposition condition for the molybdenum back contact, will give a direct impact to the efficiency of the fabricated device. In this paper, brief introduction on the production, efficiency, etc. of a Si, CdTe, and CIGS thin film solar cells and c Si solar cells are first reviewed, followed by the recent progress of substrates. Different deposition techniques' influence on the properties of molybdenum back contact for CIGS are discussed. Then, the formation and thickness influence factors of the interfacial MoSe2 layer are reviewed; its role in forming ohmic contact, possible detrimental effects, and characterization of the barrier layers are specified. Scale up challenges/issues of CIGS module production are also presented to give an insight into commercializing CIGS solar cells.

title: Review of grain interior, grain boundary, and interface effects of K in CIGS solar cells: Mechanisms for performance enhancement
abstract: Introducing K into Cu(In,Ga)(Se,S)2 (CIGS) absorbers has led to recent world record power conversion efficiencies for thin film polycrystalline solar cells. In this work, the diverse phenomena associated with K in CIGS were reviewed, and overarching mechanisms were identified. The effects of K depend on its distribution among grain interiors (GIs) grain boundaries (GBs) and interfaces. High substrate Na and low temperature favor GI K incorporation, while low Na and high temperature favor segregation of K at GBs. Depositing KInSe2 (or KIn1 yGaySe2) by co evaporation or KF post deposition treatment onto CIGS reduces buffer interface recombination in the final solar cells. KInSe2 decomposes in air, which makes characterization difficult and may affect performance. The mechanism for reduced interface recombination could be direct passivation, beneficial compound precursor, oxidation barrier, or favorable diffusion alteration.