Optimal design of buried emitter of EWT silicon solar cells type by numerical simulation

The growth of the photovoltaic industry is based on the reduction of manufacturing costs to make the energy more competitive with fossil fuels. To achieve this aim, we must reduce the production cost ratio on cell efficiency. One way is to make all contacts on rear side of solar cells to reduce the shadowing effects. One of the most recent proposed technologies is the emitter wrap through. This structure has an emitter on the front but all contacts are on the rear side. The interconnection of the emitter between the front and the rear is accomplished through holes in the substrate. These holes, usually buried with a laser, are diffused and thus allow ensuring the collection of the holders from the front face until to the rear one. This concept increases also the lateral surface of the junction. In this paper, the simulation under Atlas/Silvaco environment was used to optimize the most important geometrical and physical parameters of EWT silicon solar cells. The main difficulty was the large number of parameters affecting the performance of this type of structure. However, our study focuses on the substrate, the emitter, the back surface field (BSF) and the metal contacts. Our numerical simulation code allows to monitoring the optimal design of EWT structure. The conversion efficiency can reach a value of 18.6% by considering a p-type multicrystalline silicon substrate with a minority carrier lifetime in order of 10(-6)s. (C) 2013 The Authors. Published by Elsevier Ltd.