Impact of Edge Recombination in Small-Area Solar Cells with Emitter Windows

This paper investigates the use of emitter windows with varying passivation layers in an intensity range between 1 and 10 ^-3 suns. The results are compared with a cleaved sample without emitter windows. It is found that the passivation of the nondiffused region outside the emitter windows is very important to reduce recombination. The surface passivation schemes investigated are the three most commonly used for solar cells: aluminum oxide, silicon dioxide, and silicon nitride. The aluminum oxide and silicon dioxide resulted in a reduction in edge recombination of 8 and 4.56 times, respectively. The silicon nitride passivation resulted in worse performance than the unpassivated sample, as a result of increased recombination. The impact of the thickness of the region outside of the emitter was investigated by reducing the outside area from a 2-mm border to a 200-μm border. The aluminum oxide sample was hardly influenced, while the silicon dioxide passivated sample suffered as the carrier was now able to travel to the edge and recombine. The performance of the silicon nitride passivated sample was improved with a reduction of the outside region. However, the performance is still reduced compared with the control sample with unpassivated emitter edges.