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RbF post deposition treatment for narrow bandgap Cu(In,Ga)Se2 solar cells
摘要： Multi-junction solar cells are known to have a considerably increased efficiency potential over their typical single junction counterparts. In order to produce low cost and lightweight multi-junction devices, the availability of suitable narrow (<1.1 eV) bandgap bottom cells is paramount. A possible absorber for such a bottom cell is the Cu(In,Ga)Se2 (CIGS) compound semiconductor, one of the most efficient thin film materials to date. In this contribution we report on the RbF post deposition treatment of narrow bandgap CIGS absorbers grown with a single bandgap grading approach. We discuss the necessary deposition conditions and the observed improvements on solar cells performance. A certified record efficiency of 18.0 % for an absorber with 1.00 eV optoelectronic bandgap is presented and its suitability for perovskite/CIGS tandem devices is shown.
关键词： Post deposition treatment,Narrow bandgap,Tandem solar cells,Thin film solar cells,photovoltaics,Rubidium fluoride,Copper indium gallium selenide
更新于2025-11-14 17:28:48
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Fabrication of flexible and bifacial Cu(In,Ga)Se2 solar cell with superstrate-type structure using a lift-off process
摘要： Flexible and bifacial Cu(In,Ga)Se2 (CIGS) solar cell with superstrate-type structure utilizing ethylene tetra-fluoroethylene (ETFE) was fabricated by a lift-off process. The advantages of the lift-off process performed under low temperature (below 100 °C) are to allow to deposit the CIGS layer under high temperature and to use ETFE as superstrate. The superstrate-type structure consists of ETFE/epoxy glue/ZnO:Al (AZO)/ZnO/CdS/CIGS/back contact, where the bilayer of ultra-thin 5-nm-thick Au/400-nm-thick AZO was used as the back contact. The optical and electrical properties of the bilayer of ultra-thin Au/400-nm-thick AZO were examined for the suitable back contact. It is determined that the transmittance of the bilayer of the ultra-thin 5-nm-thick Au/AZO is reasonably suitable in view of optical property. The ohmic-like characteristic at the CIGS/ultra-thin 5-nm-thick Au/AZO interface is attained. Consequently, the flexible and bifacial CIGS solar cell is realized by a lift-off process with conversion efficiency values of 6.2% for the frontside illumination and 0.9% for the backside illumination.
关键词： ETFE film,Superstrate-type structure,Flexible and bifacial solar cell,Copper indium gallium selenide,Lift-off process
更新于2025-09-23 15:19:57
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Microwave assisted synthesis of CuInGaSe2 quantum dots and spray deposition of their composites with graphene oxide derivatives
摘要： In this contribution, we explore a spray deposition technique to prepare thin films based on nanocomposites of graphene oxide (GO) or reduced graphene oxide (rGO) with CuInGaSe2 quantum dots (QD) synthesized by a microwave-assisted method. Small nanocrystals in the tetragonal phase and emitting light at 650 nm were obtained. Water-based solutions of the nanocomposites were sprayed onto transparent conductive glass substrates using an automated ultrasonic spray system and the resulting thin films were evaluated with respect to their morphological and electrochemical properties. The distribution and organization of the graphene sheets in the composites were affected by the interaction between the nanocrystals and GO or rGO, which also interfered on the electronic properties. In addition, we demonstrated a possible application of the thin film based on the rGO-QD composite as a counter electrode in dye-sensitized solar cells.
关键词： copper indium gallium selenide,dye-sensitized solar cell,graphene oxide,microwave assisted synthesis,spray deposition,reduced graphene oxide
更新于2025-09-16 10:30:52
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Impact of Post-Deposition Recrystallization by Alkali Fluorides on Cu(In,Ga)Se2Thin-Film Materials and Solar Cells
摘要： Using thermal evaporation, Cu(In,Ga)Se2 (CIGS) layers were deposited at low temperature (350 °C) and high rate (10 μm/h) using a single stage process. They were then recrystallized using a variety of alkali fluorides: NaF, KF, RbF and CsF. To ensure that the substrate would not influence the study (via alkali diffusion), the samples were deposited on silicon wafers. The chemical, physical and electrical properties of the films were then characterized, demonstrating that all alkali fluorides behave as fluxing agents to enhance recrystallization and conductivity, and induce a (112) preferential orientation. Secondary ion mass spectrometry analysis showed that no modification of the elements' distribution occurs because of recrystallization. Solar cells were also fabricated and characterized, indicating that NaF can double the efficiency of solar cells compared to the as-deposited layers. This enhancement is accompanied by the disappearance of a rollover, voltage dependent current collection and shunt from the current density-voltage curves. However, even for the best recrystallization, the current is still limited to 28 mA/cm2, indicating that only a portion (0.75 μm) of the full device (2 μm) is activated.
关键词： Recrystallization,Copper indium gallium selenide,Alkali-fluorides,Solar cells
更新于2025-09-16 10:30:52
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Microbial Approach to Low-Cost Production of Photovoltaic Nanomaterials
摘要： Photovoltaic (PV)-generated electricity can participate in renewable grid parity after meeting conditions of low-cost PV materials and economic manufacturing of solar cells. Here, we report low-cost, scalable microbial synthesis of Cu(In,Ga)Se2 (CIGSe) and Cu(In,Ga)S2 (CIGS), which are among the promising candidates to serve as light absorbing layers in solar panels. Microbial synthesis uses reducible chalcophiles and empirically stoichiometric metal components to produce CIGSe and CIGS with band gaps and intra- and intercrystallite compositional homogeneity similar to that produced with traditional techniques. Importantly, microbially produced photovoltaic materials described herein use inexpensive precursor materials at moderate temperatures (65 °C). The microbially facilitated processes do not utilize high temperature, vacuum, or toxic organic solvents. The potential to upscale microbial synthesis without loss of material quality is demonstrated here, indicating a high potential for industrial applications of this technology for production of nanomaterials for PV applications. We estimate that a 50 000 gallon fermentor could generate about 100 kg/month of CIGSe nanoparticles, which could be processed into 0.2 MW of PV cells.
关键词： inexpensive precursor materials,copper indium gallium selenide,Thermoanaerobacter,copper indium gallium sulfide,stoichiometric homogeneity
更新于2025-09-11 14:15:04
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Heat degradation of sputter-deposited Cu(In,Ga)Se2 solar cells and modules: Impact of processing conditions and bias
摘要： We report accelerated heat degradation studies on fully encapsulated Cu(In,Ga)Se2 modules as a function of film growth parameters, in particular back contact selenization (preeSe), as well as the impact of bias (light/voltage) during heat degradation. We show that pre-Se conditions have a profound effect on the heat stability of the device, whereby reduced preeSe, while increasing initial efficiency, results in strong heat degradation, driven by a combination of reduced space-charge region and reduced minority carrier lifetime (as evident from external quantum efficiency measurements) in the light-soaked state and resulting in strong degradation of short-circuit current. This is also accompanied by a stronger increase in the shallow acceptor concentration (as measured by capacitance-voltage profiling) in the degraded state, suggesting that the SeeCu divacancy complex (VSe-VCu) is likely responsible. In this case, appearance of a high concentration of deep acceptor states accompanies increased shallow doping upon light-soaking, with the former reducing bulk lifetime and the latter further affecting electron collection due to narrow depletion width. This result suggests that bulk structural properties of the absorber film are strongly impacted by the back contact selenization conditions, making the film more susceptible to heat degradation. In the second part of this paper we show that electrical or light bias during heat exposure reduces degradation, in particular almost fully eliminating the above short-circuit current loss. This is a surprising result as usually the positive effects of bias are attributed to interfacial changes, while our results demonstrate that bulk properties can be improved as well.
关键词： Absorber,Interface,Defects,Thin film solar cell,Heat degradation,Reliability,Light soaking,Copper indium gallium selenide
更新于2025-09-11 14:15:04
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Multistage Degradation Mechanisms in Cu(In, Ga)Se2 Photovoltaic Modules Prepared by Co-Evaporation: Toward High Performances and Enhanced Stability
摘要： This study compared the stability and durability of copper indium gallium selenide (CIGS)-type solar cells prepared using one-step and three-step co-evaporation methods by investigating the causes of degradation in each layer in detail. Measurements recorded using a solar simulator showed that the sample prepared using the three-step method had better device performance owing to the large-grained structure of the CIGS absorber layer, which reduced the carrier recombination. Focusing on the discrepancy in grain size, multifarious degradation tests were conducted according to the IEC 61646 standard to evaluate the stability of the cells under harsh environments such as high humidity (85 %), high temperature (85 ℃), and mechanical load. Damp heat (85 %/85 ℃) did not affect the CIGS resistivities in either sample, whereas all the aluminum-doped zinc oxide layers degraded, as determined by confirming the chemisorbed oxygen by exposure to a hot, humid environment. After 200 thermal cycles, the CIGS layers in both samples were mainly degraded while there were no changes in the resistivities of the AZO layer in either sample. The thermal cycling test highlights that the initial resistivities of the one-step sample showed a decisive change before and after thermal cycling compared to the three-step sample. This change might be caused carriers being scattered at the grain boundaries. Although there were no big differences in the FT-IR spectra before and after thermal cycling, both XRD and XPS results confirmed that not only copper indium sulfide selenium elements of secondary phase were newly observed by sulfide diffusion from the CdS layer, but also that each element (Cu, In, Ga, and Se) was slightly oxidized by the rapid temperature variation from ?45 ℃ to 85 ℃. These results prove that the three-step co-evaporation method can produce cells with much higher stability and durability, even when operated under high humidity and temperature conditions.
关键词： Degradation mechanism,Copper indium gallium selenide,Co-evaporation,Grain size,Stability,Aluminum-doped zinc oxide
更新于2025-09-11 14:15:04
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Copper Chalcopyrites for Solar Energy Applications
摘要： Solar photovoltaic (PV) technology is a reliable and environmental friendly alternative for electricity generation. There are a number of solar PV technologies at different maturity levels, ranging from well-established and commercialized silicon PV to still in conceptual and R&D phase quantum dot and organic/polymer solar cells. Chalcopyrite solar cells, named so because of the thin absorber layer of Cu-based chalcopyrite materials used in these cells, are one of the frontrunners in thin-film PV technology owing to their tunable direct bandgap, large absorption coefficient and long-term stability. Among all Cu-chalcopyrite materials, copper indium selenide (CISe) and copper indium gallium selenide (CIGSe) are most suitable for use as light-absorbing layer. Although CISe and CIGSe absorber-based PV modules are being produced commercially for several years now, the technology is yet to mature fully as there is still scope for improvement in efficiency, manufacturability and cost reduction. The present article discusses the status of CISe-/CIGSe-based thin-film PV technology while primarily focusing on the absorber material. Different vacuum and non-vacuum methods for fabricating these materials are reviewed along with their merits/demerits and suitability to large-scale production. Current status of commercial maturity for CIGSe PV is discussed while providing general process details of selected industrial manufacturers. Existing bottlenecks for this technology are deliberated, and future directions for improvement in laboratory-scale efficiency and manufacturability are outlined.
关键词： Thin-film solar cells,Chalcopyrite,Copper indium gallium selenide,Copper indium selenide
更新于2025-09-10 09:29:36
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A challenge for x-ray photoelectron spectroscopy characterization of Cu(In,Ga)Se2 absorbers: The accurate quantification of Ga/(Ga?+?In) ratio
摘要： CIGS (Cu(In,Ga)Se2) layers are among the more efficient photovoltaic absorbers for thin film solar cells and remain competitive in the worldwide landscape of solar cells devices and modules with also new emerging markets (flexible or metallic substrates, tandem, low or high band gap CIGS…). Their properties are governed by different key composition parameters, and among them the GGI ratio ([Ga]/[Ga]+[In])) which controls the gap value. Indeed, the GGI determination is an important metrological challenge at the surface of the CIGS layer, particularly before the buffer deposition. Using X-Ray Photoelectron Spectroscopy (XPS), we propose here a specific methodology to determine this ratio at the surface. In order to, a surface preparation of the CIGS by chemical treatments, combining an initial flattening by HBr:Br2:H2O etching with a finishing step performed in KCN:H2O, is implemented. This chemical engineering leads to a quasi “perfect” surface, flattened and cleared from surface oxide and selenide phase on which our XPS methodology for GGI determination is tested. The photopeaks choice to obtain the most coherent GGI ratio quantification is discussed. In particular we focus on the Ga3d-In4d region, situated in narrow binding energy domain, and discuss why this photopeak combination can be considered as the most adapted for a representative GGI determination. Quantitative fitting procedure of the Ga3d-In4d region is qualified on a reference epitaxial InxGa1-xAs layer and its implementation in the CIGS case is shown.
关键词： X-ray photoelectron spectroscopy,Surface chemical engineering,Gallium,Indium,copper indium gallium selenide,Surface composition
更新于2025-09-10 09:29:36
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Concentration of defects responsible for persistent photoconductivity in Cu(In,Ga)Se2: Dependence on material composition
摘要： Persistent photoconductivity PPC in thin Cu(In,Ga)Se2 films is discussed within a model of relaxing defects acting as donors or acceptors depending on their configurational and charge state. The aim of this work is to identify the factors related to technological processes which affect the magnitude of PPC. We established a method of evaluation of the concentration of metastable defects in thin Cu(In,Ga)Se2 films relating it to the position of the Fermi level in thermodynamic equilibrium and used it to compare and discuss the impact of preparation details on the PPC value. The main result is that deviation from Cu/(Ga+In)Se2 stoichiometry does not change the concentration of metastable defects. Post deposition annealing in selenium affects the PPC depending on the presence of sodium during the treatment, while the impact of sodium itself on the metastable defect concentration apparently depends on whether it is present during the Cu(In,Ga)Se2 deposition process or whether it is supplied during post-deposition treatment.
关键词： Thin films,Photoconductivity,Copper indium gallium selenide,Metastability,Defects
更新于2025-09-09 09:28:46