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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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Cu2ZnGe(S1-xSe x)4 – The challenge to synthesize single phase material
摘要： The variation of the band gap energy in Cu2ZnGeSe4 and Cu2ZnGeS4 from 1.4 eV to 1.7 eV, which is controlled by different S/(S+Se) ratios renders the Cu2ZnGe(S1-xSex)4 solid solution an interesting material for the application in multi-junction solar cells. Nevertheless, this system has a certain complexity due to the existence of different polymorphs. Cu2ZnGeSe4 crystallizes in the tetragonal kesterite type structure, whereas Cu2ZnGeS4 may crystallize in the tetragonal stannite or the orthorhombic wurtz-stannite type structure, respectively. To gain deeper insights into this complex system a systematic study of the solid solution series Cu2ZnGe(S1-xSex)4 was performed using polycrystalline material prepared by solid state reaction. The chemical analysis performed by wavelength dispersive X-ray spectroscopy showed remarkable inhomogeneities with different quaternary phases co-existing within one sample. Additionally, a wide variety of binary and ternary secondary phases as well as elemental Ge was observed. The variety of secondary phases is higher in S-rich samples than in Se-rich samples of the solid solution. Thus, synthesis of Cu2ZnGe(S1-xSex)4 mixed crystals with off-stoichiometric composition is readily accompanied by the formation of various secondary phases making it a difficult task to obtain single phase material.
关键词： Wavelength dispersive X-ray spectroscopy,Solid state reaction,Polycrystalline powders,Chalcogenides,Secondary phases,Copper zinc germanium selenide,Copper zinc germanium sulfide
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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The Au/Cu2WSe4/p-Si photodiode: Electrical and morphological characterization
摘要： Cu2WSe4 nanosheets were synthesized by the hot-injection method and put as interfacial layers between Au metal and p-Si by spin coating technique to investigate their photoresponse and capacitor properties via I-V and C-V measurements, respectively. The XRD were operated to confirm crystalline structure of the Cu2WSe4. The TEM image revealed that the crystalline nanosheet structures of the Cu2WSe4. The I-V measurements were performed under dark and light illumination in the range 20 mWe100 mW light intensities with 20 mW interval. In addition, some diode parameters such as ideality factor, barrier height and series resistance were extracted via a various method and discussed in the details. The C-V measurements were employed for various frequency and voltages. The C-V characteristics of the device confirmed the strong dependence on the frequency and voltage. The results imparted that Au/Cu2WSe4/p-Si can be employed for photodiode, photodetector and capacitor applications.
关键词： Copper tungsten selenide,Photodetector,Schottky devices,Cu2WSe4,Au/Cu2WSe4/p-Si photodiode
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
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Current transport and capacitance-voltage characteristics of Sb2Se3/n-Si heterojunction diode prepared by electron beam evaporation
摘要： The Sb2Se3 thin film was successfully deposited on the n-Si substrate using an electron beam evaporated technique. The structural investigation was done by means of X-ray diffraction analysis. The surface morphology and elemental analysis of the synthesized films were studied by FESEM and EDAX, respectively. The electrical properties of the Sb2Se3/n-Si heterojunction were considered by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The I-V results of Sb2Se3/n-Si heterojunction diode show a rectifying behavior. The junction ideality factor, barrier height, and series resistance values were extracted from the rectifying curves at different temperatures. The capacitance-voltage results show the abrupt nature of the junction under consideration.
关键词： diode,ideality factor,Antimony selenide,Electron beam,FESEM,XRD
更新于2025-09-09 09:28:46
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Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se2 Nanocrystals
摘要： Crack-free films of Cu(In,Ga)Se2 (CIGS) nanocrystals were deposited with uniform thickness (>1μm) on Mo-coated glass substrates using an ink-based, automated ultrasonic spray process, then selenized and incorporated into photovoltaic devices (PVs). The device performance depended strongly on the homogeneity of the selenized films. Cracks in the spray-deposited films resulted in uneven selenization rates and sintering by creating paths for rapid, uncontrollable selenium (Se) vapor penetration. To make crack-free films, the nanocrystals had to be completely coated with capping ligands in the ink. The selenization rate of crack-free films then depended on the thickness of the nanocrystal layer, the temperature, and duration of Se vapor exposure. Either inadequate or excessive Se exposure leads to poor device performance, generating films that were either partially sintered or exhibited significant accumulation of selenium. The deposition of uniform nanocrystal films is expected to be important for a variety of electronic and optoelectronic device applications.
关键词： Nanocrystals,Selenization,Copper Indium Gallium Selenide,CIGS,Photovoltaics
更新于2025-09-09 09:28:46
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Equilibria in a ZnCl2–H2O–NaOH System, According to Data from Potentiometric Titration, and Selecting Conditions for the Hydrochemical Synthesis of ZnS and ZnSe Films
摘要： Equilibrium processes that occur in the ZnCl2–H2O–NaOH system are studied via the potentiometric titration of zinc chloride in the 0.00006–1.01 mol/L range of concentrations. Based on mathematical simulations, a number of polynuclear structures and soluble phases are identified in the system. Values of the instability constants of complex forms and the constants of the dynamic equilibria of weakly soluble zinc compounds are calculated, along with their stoichiometric compositions and areas of sustainable existence. Refined boundary conditions are determined, along with areas of the formation of ZnSe and ZnS when they are precipitated using sodium selenosulfate and thiourea, respectively. ZnSe and ZnS layers around 1000 and 200 nm thick are obtained via hydrochemical deposition on glass-ceramic substrates. Based on electron microscopy data, it is concluded that the layers consist of spherical aggregates with mean sizes of around 350–450 nm for ZnSe and 50–200 nm for ZnS, generated from primary particles with sizes of around 20–60 and 20–30 nm, respectively.
关键词： equilibrium processes,zinc selenide,complex formation,zinc sulfide,zinc chloride,potentiometric titration,thin films
更新于2025-09-04 15:30:14
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Influence of the Conditions of the Chemical Bath Deposition of Thin ZnSe Films on Their Morphology and Internal Mechanical Stresses
摘要： ZnSe films up to 2300 nm thick on glass-ceramic supports were prepared by chemical bath deposition in the ZnCl2–Na2EDTA–NaOH–NH2OH·HCl system using sodium selenosulfate as a chalcogenizer. The reflections observed in the X-ray diffraction patterns correspond to the ZnSe (stilleite) phase of cubic (space group F43m) structure with a = 5.610 ± 0.002 ?. As shown by electron-microscopic examination, ZnSe films consist of globular formations tightly adjoining to each other with the mean size of 250–400 nm depending on the deposition conditions. Elemental EDX analysis shows that the films contain, on the average, 43.68 at. % Zn, 30.50 at. % Se, and 25.82 at. % O, with the oxygen concentration somewhat decreasing at a depth of 30 nm. The internal mechanical compression stresses caused by the difference in the thermal expansion coefficients of the ZnSe film and glass-ceramic support were calculated; these stresses depend on the film thickness and at ~1040 nm reach –30.62 kN m–2. The results obtained make it possible to exclude film discontinuities, which can appear with increasing film thickness in preparation of precursor layers, and to choose the optimum support material.
关键词： chemical bath deposition,microstructure,internal mechanical stresses,film morphology,zinc selenide,films,sodium selenosulfate
更新于2025-09-04 15:30:14