Plasma Textured Glass Surface Morphologies for Amorphous Silicon Thin Film Solar Cells-A review (original) (raw)
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Vacuum, 2015
We report various SF 6 /Ar plasma textured periodic glass surface morphologies with high transmittance, haze ratio, and root mean square (rms) roughness of ITO:Zr films for amorphous silicon thin film solar cells (a-Si TFSCs). SF 6 /Ar plasma textured glass surface morphologies contain micro-and nano-textured features that help to scatter the light in visible and near infra-red (NIR) wavelength regions. We designed the textured glass surface morphologies with big square craters to smaller pyramids for various glass etching times from 30 to 75 min. Magnetron sputtered ITO:Zr (~210 nm) films were deposited on textured glass surface morphologies and showed higher transmittance and haze ratio of 88.48% and 77.61%, respectively, in the visible-NIR (400e1100 nm) wavelength region. The sheet resistance and resistivity of ITO:Zr films decreased with the increase of etching time, due to high rms roughness and better step coverage. A passivation AZO (30 nm) layer was added to the ITO:Zr films, due to its better stability against hydrogen plasma exposure. The ITO:Zr/AZO films were employed as a front TCO layer and the current densityevoltage (JeV) characteristics of a-Si TFSCs increased by light scattering effect, without any reduction in either the open circuit voltage (V OC ) or the fill factor (FF). Relative to flat glass substrate, J SC and the efficiency of a-Si TFSCs were enhanced by 7.51% and 19.39%, respectively, for textured glass surface morphology.
Journal of Renewable and Sustainable Energy, 2014
The impact of controlling the aspect ratio variation on glass substrate for a p-in a-Si:H solar cell was investigated and reported. Compared to a flat glass substrate (Corning Eagle XG), we demonstrate an increase of haze ratio from 1% to 79.1%, and an increment in the aspect ratio from 0.1 to 1.16, which is an increase to a high slope angle, using wet chemical etching. Optical transmittance measurements show a major improvement of from 92% to 96% for a wavelength of between 300 and 1100 nm, compared to the reference flat glass. A p-in a-Si:H solar cell was simulated using Advanced Semiconductor Analysis simulation based on these haze ratio and aspect ratio results, and yielded an increase in short-circuit current density (J sc) from 15.38 to 18.74 mA/cm 2 , as the aspect ratio was increased from 0.1 to 0.84. V
Journal of Energy and Natural Resources, 2015
We have introduced an approach to establish a methodology for 3D optical simulation that allows analyzing optical losses in the individual layers of a thin-film solar cell structure. Using commercial Finite-Difference Time-Domain (FDTD) tool, where Maxwell's Curl equations were rigorously solved for optimizing such cells, a computer modeling has been performed. We have reported the ways to investigate efficient light-trapping schemes by using periodically textured transparent conductive oxide (TCO) in thin-film amorphous silicon solar cells. The optical effects in small area thin film silicon p-in solar cells deposited on glass substrates coated with aluminum doped zinc oxide (ZnO:Al) have been addressed. In order to enhance the efficiency, TCO surface morphology has been analyzed, where pyramidal and parabolic textured surfaces have been used. For these cells, the quantum efficiency, short-circuit current, total reflectance, and all absorption losses have been successfully computed and analyzed. The investigation was carried out based on our proposed model that exhibits maximum current density of 17.32 mA/cm 2 for the absorbing layer thickness of 300 nm.
Plasma Texturing and Porous Silicon Mirrors for Epitaxial Thin Film Crystalline Silicon Solar Cells
MRS Proceedings, 2008
Thin film silicon solar cells, consisting of an epitaxially grown active layer on a low quality highly doped silicon substrate, incorporate many attractive features usually associated with their sister cells based on bulk silicon. However, the efficiency of the current epitaxial semi-industrial screen printed cells is limited to 11-12% mainly due to optical shortcomings. This paper will give an overview of our work aimed at tackling the 2 most important problems: (i) Finding and implementing an adequate front surface texture and (ii) the simulation, fabrication and incorporation of an intermediate reflector.The former issue has been addressed by the development of plasma texturing based on halogen species. This method allows us to fulfil the sometimes contradictory requirements for the textured surface, i.e. a uniform and reduced reflection, a strong lambertian character to scatter the light and a limited removal of silicon. It will be shown that the scattering efficiency is depende...
Recent progress in amorphous and microcrystalline silicon based solar cell technology
This contribution discusses recent scientific and technological challenges for the development of highly efficient amorphous (a-Si:H) and microcrystalline silicon (µc-Si:H) based thin film solar cells. Aluminium doped ZnO films prepared by sputtering and post deposition etching serve as transparent conductive oxide (TCO) material, which provide excellent light trapping properties. Challenges are the transfer of this approach to costeffective reactive sputtering from metallic targets and the reduction of optical absorption losses in the front TCO films. We developed µc-Si:H solar cells by plasma-enhanced chemical vapour deposition (PECVD) using 13.56 MHz and 40.68 MHz excitation frequency in a process regime of high deposition pressures and high RFpowers. These conditions provide sufficiently "soft" deposition for the growth of high quality µc-Si:H material and yield high deposition rates. A stable aperture area module efficiency of 10.1 % was obtained for an a-Si:H/µc-Si:H module on 10x10 cm 2 substrate size. In case of the µc-Si:H PECVD process we discuss the questions of process stability, process reproducibility and up-scaling to large area production systems.
Plasma Texturing of Silicon Solar Cells
1999
Surface texture promotes enhanced light absorption in Si solar cells. The quality of lower cost multicrystalline-silicon (mc-Si) has increased to the point that its cell performance is close to that of single c-Si cells, with the major difference resulting from the inability to texture mc-Si ...
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices III, 2014
Light scattering at randomly textured interfaces is essential to improve the absorption of thin-film silicon solar cells. Aluminium-induced texture (AIT) glass provides suitable scattering for amorphous silicon (a-Si:H) solar cells. The scattering properties of textured surfaces are usually characterised by two properties: the angularly resolved intensity distribution and the haze. However, we find that the commonly used haze equations cannot accurately describe the experimentally observed spectral dependence of the haze of AIT glass. This is particularly the case for surface morphologies with a large rms roughness and small lateral feature sizes. In this paper we present an improved method for haze calculation, based on the power spectral density (PSD) function of the randomly textured surface. To better reproduce the measured haze characteristics, we suggest two improvements: i) inclusion of the average lateral feature size of the textured surface into the haze calculation, and ii) considering the opening angle of the haze measurement. We show that with these two improvements an accurate prediction of the haze of AIT glass is possible. Furthermore, we use the new equation to define optimum morphology parameters for AIT glass to be used for a-Si:H solar cell applications. The autocorrelation length is identified as the critical parameter. For the investigated a-Si:H solar cells, the optimum autocorrelation length is shown to be 320 nm.
Applied Physics A, 2015
Various SF 6 /Ar plasma-textured periodic glass surface morphologies for high transmittance, haze ratio and low sheet resistance of ITO:Zr films are reported. The SF 6 /Ar plasma-textured glass surface morphologies were changed from low aspect ratio to high aspect ratio with the increase in RF power from 500 to 600 W. The micro-and nano-size features of textured glass surface morphologies enhanced the haze ratio in visible as well as NIR wavelength region. Micro-size textured features also influenced the sheet resistance and electrical characteristics of ITO:Zr films due to step coverage. The ITO:Zr/AZO bilayer was used as front TCO electrode for p-i-n amorphous silicon thin film solar cells with current density-voltage characteristics as: V oc = 875 mV, FF = 70.90 %, J sc = 11.31 mA/cm 2 , g = 7.02 %.