Reactive ion etching (RIE) as a method for texturing polycrystalline silicon solar cells (original) (raw)
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Large-area multicrystalline silicon solar cell fabrication using reactive ion etching (RIE)
Solar Energy Materials and Solar Cells, 2011
Surface texturing of crystalline silicon wafer improves the conversion efficiency of solar cells by the enhancement in antireflection property and light trapping. Compared to antireflection coating, it is a more permanent and effective scheme. Wet texturing with the chemicals such as alkali (NaOH, KOH) or acid (HF, HNO 3 , CH 3 COOH) is too difficult for thinner wafer to apply due to a large amount of silicon loss. However, Plasma surface texturing using Reactive Ion Etching (RIE) can be effective in reducing the surface reflectance with low silicon loss. In this study, we have fabricated a large-area (156 Â 156 mm) multicrystalline silicon (mc-Si) solar cell by mask less surface texturing using a SF 6 /O 2 reactive ion etching. We have accomplished texturing with RIE by reducing silicon loss by almost half of that in wet texturing process. By optimizing the processing steps, we achieved conversion efficiency, open circuit voltage, short circuit current density, and fill factor as high as 16.1%, 619 mV, 33.5 mA/cm 2 , and 77.7%, respectively. This study establishes that it is possible to fabricate the thin multicrystalline silicon solar cells of low cost and high efficiency using surface texturing by RIE.
Improved anisotropic etching process for industrial texturing of silicon solar cells
Solar Energy Materials and Solar Cells, 1999
An experimental study on the surface texturisation of monocrystalline wafers with solutions containing sodium-hydroxide and isopropanol was carried out. Both the composition and the temperature of the etching solution were optimised on the basis of etch-rate measurements on silicon samples having different crystallographic directions. It was found that the density and the size of the pyramids are influenced by the etch-rate of silicon in the 11 0 02 direction and also by the anisotropy factor of the solutions being the quotient of the etch rate in the 11 0 02 to 11 1 12 directions. Design of experiments and response surface methods were used to extract the etch rate as a function of different input parameters, such as the sodium hydroxide and isopropanol concentrations and the temperatures of the solutions. Optimum texturing conditions were found at a temperature of 80°C and a composition which causes a relatively high etch rate in the 11 0 02 direction with an anisotropy factor of 10. At the starting point of the etching process, the inhomogeneity of pyramid nucleation can be avoided by mixing an additive to the texturing solution. With such a solution, the pyramid size can be tuned by varying the etching time in order to obtain a low reflectivity from the textured silicon wafers. Based on our results the texturing process could be stabilised with respect to the reproducibility on a large scale of wafers.
RIE surface texturing for optimum light trapping in multicrystalline silicon solar cells
Journal of the Korean Physical Society, 2012
Optical losses by reflection and transmission of the incident light should be reduced to improve the efficiency of solar cells. Compared with antireflection coatings, surface texturing is a more persistent and effective solution aiming at reducing light reflection losses. Alkali (NaOH, KOH) or acidic (HF, HNO3, CH3COOH) chemicals are used in conventional solar cell production lines for wet chemical texturing. However, Surface texturing is too difficult to apply to solar cell fabrication with thinner wafers due to the large amount of silicon loss caused by saw damage removal (SDR) and the texturing process for multicrystalline silicon (mc-Si). In order to solve the problems, reactive ion etching (RIE) has been applied for surface texturing of solar cell wafers. The RIE method can be effective in the reducing surface reflection with low silicon loss. In this study, we, therefore, fabricated a large-area (243.3 cm 2) mc-Si solar cell by maskless surface texturing using a SF6/O2 RIE process. Also, we achieved a conversion efficiency (Eff), open circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF) as high as 17.2%, 616 mV, 35.1 mA/cm 2 , and 79.6%, respectively, which are suitable for fabricating thin crystalline silicon solar cells at low cost and with high efficiency.
Pyramidal texturing of silicon solar cell with TMAH chemical anisotropic etching
Solar Energy Materials and Solar Cells, 2006
High-efficiency silicon solar cells need a textured front surface to reduce reflectance and to improve light trapping. Texturing of monocrystalline silicon is usually done in alkaline solutions. These solutions are cheaper, but are pollutants of silicon technologies. In this paper, we investigate an alternative solution containing tetramethyl ammonium hydroxide ((CH 3) 4 NOH, TMAH). This study shows the influence of different parameters (concentration, agitation, duration and temperature), to obtain uniform and reliable pyramidal texturization on different silicon surfaces (as cut, etched and polished). Under optimized conditions, TMAH-textured surface led to an average weighted reflectance of 13%, without any antireflection coating independent of the initial silicon surface. Unlike potassium hydroxide (KOH) texturing solution, characterization of silicon oxide layer contamination after TMAH texturing process revealed no pollution, and passivation is less affected by TMAH than by KOH texturization.
The reactive ion etching (RIE) technology which enables nano-texturatization of surface is applied on monocrystalline silicon solar cell. The additional RIE process on alkalized textured surface further improves the blue response and short circuit current. Such parameter is characterized by surface reflectance and quantum efficiency measurement. By varying the RIE process time and matching the subsequent processes, the absolute efficiency gain of 0.13% is achieved. However, the result indicates potential efficiency gain could be higher due to process integration. The critical etch process time is discussed which minimizes both front surface reflectance and etching damage, considering the challenges of required system throughput in industry.
Optical and Electrical Properties of Silicon Solar Cells by Wet Chemical Etching
Journal of the Chilean Chemical Society, 2019
We present a simple method for the texturing of commercial silicon solar cells in a two-step process by etching in an HF solution containing H 2 O 2. This etching process is facilitated by silver nanoparticles which act as catalytic sites. The etching times for the fabrication of nano-pores on the surface are established. The optical properties of the nano-structures on the surface of silicon solar cell were investigated by spectrometer measurements. The samples presented a total reflection coefficient lower than that of silicon solar cells without the treatment. The global efficiency of the silicon solar cell depends on the chosen preparation conditions for the silver ion concentration, and time of wet etching. The textured surface of solar cells showed an increase in efficiency, with a circuit photocurrent higher than that of a reference silicon solar cell without texturing. The J-V curves of various silicon cells are presented and discussed in correlation with the surface morphology.
Rie-texturing of multicrystalline silicon solar cells
Solar Energy Materials and Solar Cells, 2002
We developed a maskless plasma texturing technique for multicrystalline silicon (mc-Si) cells using Reactive Ion Etching (RIE) that results in higher cell performance than that of standard untextured cells. Elimination of plasma damage has been achieved while keeping front reflectance to extremely low levels. Internal quantum efficiencies as high as those on planar cells have been obtained, boosting cell currents and efficiencies by up to 7% on evaporated metal and 4% on screen-printed cells.
Solar Energy Materials and Solar Cells, 2010
Solar cells require surface texturing in order to reduce light reflectance, and to enhance light trapping. Anisotropic wet chemical etching is commonly used to form pyramids on the (1 0 0) silicon wafer surface by etching back to the (1 1 1) planes. In this paper, we used a low density silicon dioxide layer to allow etching in localized regions as an etch mask, forming inverted pyramid etch pits. Such an oxide can be deposited by plasma enhanced chemical vapor deposition using low deposition temperatures. The inverted pyramids are ideal for reducing surface reflectance, and are used in the highest efficiency silicon solar cells. Depending on the etch time and oxide quality, a variety of surface texture morphologies can be achieved. Due to the oxide mask, very little silicon is removed. This is an economical ideal method for texturing thin film single-crystalline silicon solar cells, as it combines the benefits of low reflectance with minimal thickness removed, while no photolithography is employed.
Thin Solid Films, 2013
To maximize the conversion efficiency of solar cells by improving the trapping of incident light, surface texturing of multicrystalline silicon wafers is a more permanent and effective solution to decrease reflections compared with antireflection coatings. In general, many techniques of wet chemical surface texturing depend on crystal orientation. Also, these processes place a limitation on the growth of solar production capacity due to consumption of the large amount of material, de-ionized water and chemicals. Reactive ion etching (RIE) is therefore useful for mc-Si solar cells with the random grain orientation. In this study, we have fabricated mc-Si solar cells with a large-area (156 mm × 156 mm) by a random RIE texturing method using SF 6 /O 2 plasma chemistry. A large amount of silicon loss, which is due to saw damage removal and texturing process of mc-Si wafers, have dramatically decreased by applying RIE texturing process. As a result of the optimum RIE process, the best mc-Si solar cell showed conversion efficiency, fill factor, short circuit current density, and open circuit voltages as high as 17.4%, 80%, 35 mA/cm 2 and 620 mV, respectively. This study demonstrates that it is possible to apply the thin mc-Si Solar cells fabrication for low cost and high efficiency in conventional industrial production line.