International Journal of Machine Tools & Manufacture 42 (2002) 1657–1664 EDM texturing of multicrystalline silicon wafer and EFG ribbon for solar cell application J. Qian, S. Steegen, E. Vander Poorten, D. Reynaerts * , H. Van Brussel Division PMA, Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300B, B-3001 Heverlee, Belgium Received 8 April 2002; accepted 22 July 2002 Abstract This paper presents a novel electrical discharge machining (EDM) texturing method for roughening mc-Si wafers and EFG ribbons for solar cell application. Experiments were carried out on an EDM die-sinker using a specially designed conductive and soft magnetic brush to texture the workpiece. The textured substrates were investigated and analysed using scanning electron microscope, and solar cells were made on textured samples to evaluate the effect of this method. Preliminary experimental results show that the throughput of this method can be over 1000 mm 2 minute with a brush of 100 mm diameter. Solar cells made on textured substrates give reasonable output.  2002 Elsevier Science Ltd. All rights reserved. Keywords: Electrical discharge machining; EDM; Texturing; Multicrystalline silicon; EFG ribbon; Solar cell 1. Introduction A recently finished MusicFM study of the European Commission has clearly demonstrated that the increasing market size towards 500 MWp/year will lead to a drastic crystalline silicon photovoltaic (PV) module price reduction below 1 ECU/Wp [1], if the solar cell process is based on printing metallization and thin large-area substrates from silicon sheets, ribbons or multicrystalline wafers. Although laboratory and industrial production processes have already demonstrated required efficiency levels, there are still severe barriers and bottlenecks in industrial production lines with respect to throughput, yield, investment cost and energy consumption for the available production equipment. The reason for this is the lack of specially designed and developed equipment for the PV industry. Almost all of the equipment in use today were originally made for the ‘High-Tech’ sem- iconductor or hybrid industry according to their specific requirements, with only minor adjustments to solar cell production [2]. * Corresponding author. Tel: +32-16-32-26-40; fax: +32-16-32- 29-87. E-mail address: Dominiek.Reynaerts@mech.kuleuven.ac.be (D. Reynaerts). 0890-6955/02/$ - see front matter.  2002 Elsevier Science Ltd. All rights reserved. PII:S0890-6955(02)00116-5 While a wide variety of semiconductor materials have been examined and are still currently under development for PV modules, most solar-cell modules manufactured today utilize monocrystalline silicon (cSi), although there has recently been some success with amorphous silicon solar cells [3]. Monocrystalline silicon solar cells are fabricated using the same techniques as commercial silicon integrated circuits. Most solar-cell substrates start as 250–350 μm wafers sliced from a silicon ingot. Despite the relative maturity of cSi PV technology, industry continues to make improvements in its manu- facturing processes and module design to reduce manu- facturing cost and increase throughput. One novel approach for creating solar-cell substrates, the edge- defined film-fed growth (EFG) technique, grows the multicrystalline silicon by extracting the crystallizing silicon which is melt through a graphite die. By this tech- nique, ribbons of multicrystalline silicon can be grown as octagonal tube. The tube is later cut into sheets, reduc- ing the amount of silicon lost in the sawing process. After sawing, the silicon is doped to form n and p regions, followed by the deposition of metal contacts on both the top and bottom of the wafer. The top metal contact is deposited selectively to allow light to enter the cell. Although the multicrystalline substrates and ribbons