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27th European Photovoltaic Solar Energy Conference and Exhibition; 1494-1497, Shinsung Solar Energy R&D center works on a high efficiency solar cell. One of the technologies is based on the selective emitter from laser doping technique and Ni/Cu plated contact. Now, Shinsung Solar Energy achieved the energy conversion efficiency of 19.64% (confirmed by Fraunhofer ISE) at the 6inch wafer by the front side selective emitter by laser doping and plated Ni/Cu metal contacts by LIP(Light Induced Plating). We use 6 inch standard commercial grade 0.5 - 3 Ω-cm boron-doped CZ silicon wafers. In this case we have to solve the problem for plating which is shunting on the edge side of the wafer. In this paper we represent 3 different ways to get a lightly doped emitter; back side oxide masking, single side (back side) etching, and single side doping using ion implantation process. And we optimize the aspect ratio of plated Cu contact by varying the HF dipping, Ni plating by LIP and Cu plating by LIP condition.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1266-1269, For high efficiency and low cost multi-crystalline silicon solar cell, we applied selective emitter on conventional screen printed solar cell. We have fabricated the industrial sized multi-crystalline solar cells (6 inch, 156mm x 156mm) with selective emitter structure by using a conventional diffusion process (POCl3) and screen printed contact. In the 2.35mm same finger spacing, selective emitter solar cells have the higher Voc and Isc than homogeneous emitter solar cells. But due to low FF, improved efficiency was only 0.3%. In order to have maximum selective emitter effect, we investigated finger spacing optimization with the higher FF. In this study, we investigated the front grid pattern by applying a selective emitter structure to minimize power loss. Optimized selective emitter cells have 0.7% improved efficiency than homogeneous emitter solar cells. This efficiency gain is related to a more suitable finger spacing with emitter which lead to an improved Isc and Voc without a drop in FF. The increase of the current is due to a better blue response. High efficient (17.57%) multicrystalline silicon solar cells with a selective emitter structure have been successfully fabricated.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1297-1299, Solar cell metallization is a major efficiency-limiting and cost-determining step in solar cell processing. Screen printed metallization is the most widely used contact formation technique for commercial Si solar cell. However, the screen-printed contacts are 125-150 um wide, which gives rise to high shading losses. And fill factors are low (~0.75) because of high contact resistance, low metal conductivity, and junction shunting. This work demonstrates that the high efficiency (~19.1%) mono-crystalline Si solar cell (Area=15.6 x 15.6 cm2) with a selective emitter structure used in the conventional diffusion process (POCl3) and the screen printed contact is presented in this paper. In particular, we focus on the improvement of fill factor (FF) by the front metal Ag portion and aspect ratio optimization.

26th European Photovoltaic Solar Energy Conference and Exhibition; 1390-1393, In comparison with other techniques for forming selective emitter structures, the UNSW laser doped selective emitter approach is a very simple and cost-effective to apply to standard industrial screen-printed solar cell production line with the inclusion of laser doping and plating equipment. In this paper, we investigate two different processing methods for the formation of the aluminium back surface field for the fabrication of laser doped selective emitter solar cells on industrial equipment. Each step of cell fabrication is monitored using a photoluminescence imaging system to understand the effects of individual processes on overall cell performance and hence obtain the optimal process parameters for various processes. It is observed that using non-optimal firing conditions for the formation of the aluminium back surface field can lead to the formation of low lifetime regions in areas where the SiN is in direct contact with the belt. However, by avoiding contact of the SiN layer to the belt during the firing step, these low lifetime regions are avoided, and open circuit voltages of 638 mV are obtained with fill factors of more than 78% on large area devices.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2694-2697, The process conditions for high efficiency industrial crystalline Si solar cells with selective emitter were optimized. In the screen printed solar cells, the sheet resistance must be 50~60 ohm/sq. because of metal contact resistance. But the low sheet resistance causes the increase of the recombination and blue response at the short wavelength. Therefore, the screen printed solar cells with homogeneous emitter have limitations of efficiency, and this means that the selective emitter must be used to improve cell efficiency. This work demonstrates the feasibility of a commercially available selective emitter process, based on screen printing and conventional diffusion process. At the last 35th IEEE photovoltaic specialists conference, we announced about 18.5% efficient selective emitter solar cell by variation of heavy emitter pattern width. Now, we improved cell efficiency from 18.5% to 19% by transition of heavy emitter pattern and shallow emitter doping condition. A maximum cell efficiency of 19.05% is obtained on a 156mm x 156mm crystalline silicon solar cell.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2688-2691, This study used phosphorous diffusion paste 99-038 from Ferro Company to verify the productivity and cost reduction. The experimental results have showed remarkable capabilities of diffusion paste. By the comparable cell efficiency such as 17.4%, if it further improved the performance and process control, screen printed emitter solar cells could be produced that represent over 18% efficiency with quite adequate firethrough condition through low cost processes than current thermal diffusion. Moreover, some parts of general mass production line should be designed simple if using diffusion paste with only a few high throughput inline printers and infrared furnaces in the future.