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- Cu(In
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- Yeungnam University
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- MiaSolé Hi‐Tech
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- Nanjing University of Aeronautics & Astronautics
- Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW)
- Korea Institute of Energy Research (KIER)
- Normandie Univ, UNIROUEN, INSA Rouen
- Korea Institute of Science and Technology
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The role of NaF post-deposition treatment on the photovoltaic characteristics of semitransparent ultrathin Cu(In,Ga)Se <sub/>2</sub> solar cells prepared on indium-tin-oxide back contacts: a comparative study
摘要: Cu(In,Ga)Se2 (CIGSe) solar cells with absorber thicknesses of <500 nm are important for lowering the cost of photovoltaic (PV)-generated electricity. Moreover, ultrathin bifacial CIGSe solar cells can be prepared on indium-tin-oxide (ITO) back contacts (BCs). In contrast to Mo BCs, ITO BCs suppress the di?usion of Na from soda-lime glass (SLG) to the CIGSe absorber. Na present in the absorber is supposed to ameliorate the PV properties of CIGSe solar cells, but in the absence of Na or when the Na concentration is extremely low, the PV performance is expected to be poor. In this study, a NaF post-deposition treatment (PDT) was applied to a <500 nm thick semitrasparent CIGS absorber prepared by a 1-stage co-evaporation process. A detailed comparison is made between the CIGSe solar cell that underwent the NaF PDT (C–Na) and a reference CIGSe solar cell in which no Na was supplied from an external source (C0). All the PV parameters (i.e., the open-circuit voltage, short-circuit current density, ?ll factor, and e?ciency) of C–Na considerably improved compared with those of C0. To understand the factors that led to this improvement, the solar cells are analyzed by various characterization techniques, including JV measurements, external quantum e?ciency measurements, temperature-dependent measurements of the open-circuit voltage, capacitance–voltage measurements, drive level capacitance pro?lometry, and admittance spectroscopy. Furthermore, the reaction occurring at the CIGSe/ITO interface is investigated with transmission electron microscopy, and the implications of this reaction on the device performance are discussed.
关键词: ultrathin,solar cells,semitransparent,indium-tin-oxide back contacts,NaF post-deposition treatment,Cu(In,Ga)Se2,photovoltaic characteristics
更新于2025-09-11 14:15:04
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Influence of heavy alkali post deposition treatment on wide gap Cu(In,Ga)Se2
摘要: The effect of Potassium, Rubidium, and Cesium post deposition treatment (PDT) on wide bandgap Cu(In,Ga)Se2 (CIGSe) absorbers has been investigated. The results show that the efficiency of the cells can be improved by the alkali treatment and a higher value of the open-circuit-voltage (VOC) can be achieved. In spite of this improvement, the activation energy (EA) of the treated samples remained smaller than the bandgap (Eg) and VOC(t) transients under red light showed a negative slope. Hence, the wide gap CIGSe devices remain limited by recombination at the interface. However, the VOC(t)-transient of treated and untreated samples with the same Eg show a different slope (d Δ?????? (??)/dt). CIGSe samples treated with heavy alkalis (RbF- and CsF-PDT) illustrate a smaller slope in comparison to no-PDT and KF-PDT samples. In this contribution, we discuss the Voc(t) slope, i.e. d Δ?????? (??)/dt, with reference to the illumination dependent doping density (NA,a) and to a possible Sodium exchange mechanisms.
关键词: alkali treatment,wide bandgap,Ga)Se2,Cu(In,recombination,post deposition treatment,solar cells,open-circuit-voltage
更新于2025-09-09 09:28:46
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Modeling Diffusion of Impurities in Molybdenum Thin Films as a Function of Substrate Temperature
摘要: Alkali ions are key to improving the performance of polycrystalline Cu(In,Ga)Se2 (CIGS) solar cells. Typically, a soda–lime glass substrate acts as an intrinsic source for many alkali ions. For these ions to reach the CIGS layer, diffusion through a metallic back contact is necessary. Typically deposited via sputtering, the morphology of this metallic back contact is dependent on multiple including substrate temperature. By deposition parameters, preparing ?lms with varying deposition parameters, and utilizing both, multiple material characterizations (X-ray diffraction, scanning electron microscopy, and secondary ion mass spectrometry) and numerical modeling, we demonstrate here that effective paths of diffusion are just as important as diffusion rate for the alkali ions. As the substrate temperature increases, the mechanism that hinders the ability for alkali ions to diffuse switches effectively from diffusion rate to effective path of diffusion. It is shown that the lack of viable diffusion paths at substrate temperatures above 100 °C becomes the dominant factor for the transport of alkali ions.
关键词: solar cell,impurities,Back contact,modeling,diffusion,molybdenum,Cu(In,Ga)Se2 (CIGS)
更新于2025-09-04 15:30:14
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The role of oxygen doping on elemental intermixing at the PVD-CdS/Cu (InGa)Se <sub/>2</sub> heterojunction
摘要: Elemental intermixing at the CdS/CuIn1?xGaxSe2 (CIGS) heterojunction in thin‐film photovoltaic devices plays a crucial role in carrier separation and thus device efficiency. Using scanning transmission electron microcopy in combination with energy dispersive X‐ray mapping, we find that by controlling the oxygen in the sputtering gas during physical vapor deposition (PVD) of the CdS, we can tailor the degree of elemental intermixing. More oxygen suppresses Cu migration from the CIGS into the CdS, while facilitating Zn doping in the CdS from the ZnO transparent contact. Very high oxygen levels induce nanocrystallinity in the CdS, while moderate or no oxygen content can promote complete CdS epitaxy on the CIGS grains. Regions of cubic Cu2S phase were observed in the Cu‐rich CdCuS when no oxygen is included in the CdS deposition process. In the process‐of‐record sample (moderate O2) that exhibits the highest solar conversion efficiency, we observe a ~26‐nm‐thick Cu‐deficient CIGS surface counter‐doped with the highest Cd concentration among all of the samples. Cd movement into the CIGS was found to be less than 10 nm deep for samples with either high or zero O2. The results are consistent with the expectation that Cd doping of the CIGS surface and lack of Zn diffusion into the buffer both enhance device performance.
关键词: scanning transmission electron microscopy,Cu diffusion,Cu (In,Ga)Se2 photovoltaics,CdS structure,STEM‐EDS mapping
更新于2025-09-04 15:30:14