인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

We report on the use and effect of the alkali elements rubidium and caesium in the place of sodium and potassium in the alkali post deposition treatment (PDT) as applied to Cu(In,Ga)Se2 (CIGS) solar cell absorbers. In order to study the effects of the different alkali elements, we have produced a large number of CIGS solar cells with high efficiencies resulting in a good experimental resolution to detect even small differences in performance. We examine the electrical device parameters of these fully functional devices and observe a positive trend in the I –V parameters when moving from devices without PDT to KF-, RbF-, and eventually to CsF-PDT. A diode analysis reveals an improved diode quality for cells treat-ed with heavier alkalis. Furthermore, secondary ion mass spectrometry (SIMS) measurements reveal a competitive mechanism induced within the class of alkali elements in the CIGS absorber induced by the alkali post deposition treatment. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

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Effects of heavy alkali elements in Cu(In,Ga)Se2 solar cells with efficiencies up to 22.6%

The path towards a high-performance solution-processed kesterite solar cell ☆

The kesterite-structured semiconductors Cu2ZnSnS4 and Cu2ZnSnSe4 are drawing considerable attention recently as the active layers in earth-abundant low-cost thin-film solar cells. The additional number of elements in these quaternary compounds, relative to binary and ternary semiconductors, results in increased flexibility in the material properties. Conversely, a large variety of intrinsic lattice defects can also be formed, which have important influence on their optical and electrical properties, and hence their photovoltaic performance. Experimental identification of these defects is currently limited due to poor sample quality. Here recent theoretical research on defect formation and ionization in kesterite materials is reviewed based on new systematic calculations, and compared with the better studied chalcopyrite materials CuGaSe2 and CuInSe2 . Four features are revealed and highlighted: (i) the strong phase-competition between the kesterites and the coexisting secondary compounds; (ii) the intrinsic p-type conductivity determined by the high population of acceptor CuZn antisites and Cu vacancies, and their dependence on the Cu/(Zn+Sn) and Zn/Sn ratio; (iii) the role of charge-compensated defect clusters such as [2CuZn +SnZn ], [VCu +ZnCu ] and [ZnSn +2ZnCu ] and their contribution to non-stoichiometry; (iv) the electron-trapping effect of the abundant [2CuZn +SnZn ] clusters, especially in Cu2ZnSnS4. The calculated properties explain the experimental observation that Cu poor and Zn rich conditions (Cu/(Zn+Sn) ≈ 0.8 and Zn/Sn ≈ 1.2) result in the highest solar cell efficiency, as well as suggesting an efficiency limitation in Cu2ZnSn(S,Se)4 cells when the S composition is high.

Classification of lattice defects in the kesterite Cu2ZnSnS4 and Cu2ZnSnSe4 earth-abundant solar cell absorbers.

Thin-film photovoltaic devices based on chalcopyrite Cu(In,Ga)Se2 (CIGS) absorber layers show excellent light-to-power conversion efficiencies exceeding 20%. This high performance level requires a small amount of alkaline metals incorporated into the CIGS layer, naturally provided by soda lime glass substrates used for processing of champion devices. The use of flexible substrates requires distinct incorporation of the alkaline metals, and so far mainly Na was believed to be the most favourable element, whereas other alkaline metals have resulted in significantly inferior device performance. Here we present a new sequential post-deposition treatment of the CIGS layer with sodium and potassium fluoride that enables fabrication of flexible photovoltaic devices with a remarkable conversion efficiency due to modified interface properties and mitigation of optical losses in the CdS buffer layer. The described treatment leads to a significant depletion of Cu and Ga concentrations in the CIGS near-surface region and enables a significant thickness reduction of the CdS buffer layer without the commonly observed losses in photovoltaic parameters. Ion exchange processes, well known in other research areas, are proposed as underlying mechanisms responsible for the changes in chemical composition of the deposited CIGS layer and interface properties of the heterojunction.

Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells

https://recipp.ipp.pt/bitstream/10400.22/3428/3/ART_PauloFernandes_2011_DFI.pdf

Study of polycrystalline Cu2ZnSnS4 films by Raman scattering

https://recipp.ipp.pt/bitstream/10400.22/3406/3/ART_PauloFernandes_2009_DFI.pdf

Growth and Raman scattering characterization of Cu2ZnSnS4 thin films

Thin films of Cu2SnS3 and Cu3SnS4 were grown by sulfurization of dc magnetron sputtered Sn–Cu metallic precursors in a S2 atmosphere. Different maximum sulfurization temperatures were tested which allowed the study of the Cu2SnS3 phase changes. For a temperature of 350 °C the films were composed of tetragonal (I-42m) Cu2SnS3. The films sulfurized at a maximum temperature of 400 °C presented a cubic (F-43m) Cu2SnS3 phase. On increasing the temperature up to 520 °C, the Sn content of the layer decreased and orthorhombic (Pmn21) Cu3SnS4 was formed. The phase identification and structural analysis were performed using x-ray diffraction (XRD) and electron backscattered diffraction (EBSD) analysis. Raman scattering analysis was also performed and a comparison with XRD and EBSD data allowed the assignment of peaks at 336 and 351 cm−1 for tetragonal Cu2SnS3, 303 and 355 cm−1 for cubic Cu2SnS3, and 318, 348 and 295 cm−1 for the Cu3SnS4 phase. Compositional analysis was done using energy dispersive spectroscopy and induced coupled plasma analysis. Scanning electron microscopy was used to study the morphology of the layers. Transmittance and reflectance measurements permitted the estimation of absorbance and band gap. These ternary compounds present a high absorbance value close to 104 cm−1. The estimated band gap energy was 1.35 eV for tetragonal (I-42m) Cu2SnS3, 0.96 eV for cubic (F-43m) Cu2SnS3 and 1.60 eV for orthorhombic (Pmn21) Cu3SnS4. A hot point probe was used for the determination of semiconductor conductivity type. The results show that all the samples are p-type semiconductors. A four-point probe was used to obtain the resistivity of these samples. The resistivities for tetragonal Cu2SnS3, cubic Cu2SnS3 and orthorhombic (Pmn21) Cu3SnS4 are 4.59 × 10−2 Ω cm, 1.26 × 10−2 Ω cm, 7.40 × 10−4 Ω cm, respectively.

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A study of ternary Cu2SnS3 and Cu3SnS4 thin films prepared by sulfurizing stacked metal precursors

Cu(In,Ga)Se2 (CIGS) absorber layers for thin-film solar cells were grown without sodium. Na was diffused into some of the absorbers after growth, which led to strongly improved device performance compared with Na-free cells. Efficiencies of 13.3% and 14.4% were achieved at substrate temperatures as low as 400 and 450 °C, respectively. With the post-deposition treatment, the effects of Na on CIGS growth are excluded, and most of the Na is expected to reside at grain boundaries. The dominating cause for Na-induced device improvements might be passivation of grain boundaries.

Efficiency enhancement of Cu(In,Ga)Se2 solar cells due to post-deposition Na incorporation

Two different magnetron sputtering techniques with RF and DC plasma discharge modes were tested for room temperature deposition of ITO layers from In2O3:SnO2 targets (10 wt% SnO2). The influence of sputtering conditions (mainly the sputtering power and oxygen content in the Ar–O2 gas mixture) on the transparency and conductivity of the formed layers was investigated. The ITO films obtained both by RF and DC magnetron sputtering at room temperature have a high transparency in the visible wavelength range (80–85%) and a low surface resistance (20–25 X/sq for � 300 nm thickness) but their optimized deposition conditions and structural properties are significantly different. The DC sputtering can be performed in pure Ar with a lower discharge power density (1.0 W/cm 2 ) and relatively high deposition rate (� 60 nm/min) while the RF sputtering requires Ar–O2 (3.0 vol.% O2) gas mixture, higher discharge power density (1.5 W/cm 2 ) and yields a lower deposition rate (� 20 nm/min). The RF sputtered ITO layers show a crystalline structure with strong (2 2 2), (4 0 0), (4 4 0), (6 2 2) X-ray diffraction peak intensities while the DC layers are amorphous with surface morphology formed by nano-scale grains.

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A. F. da Cunha

Papers

Study of polycrystalline Cu2ZnSnS4 films by Raman scattering

Growth and Raman scattering characterization of Cu2ZnSnS4 thin films

A study of ternary Cu2SnS3 and Cu3SnS4 thin films prepared by sulfurizing stacked metal precursors

Efficiency enhancement of Cu(In,Ga)Se2 solar cells due to post-deposition Na incorporation

Comparative study of ITO layers deposited by DC and RF magnetron sputtering at room temperature