Influence of the emitter formation technique on the performance of silicon solar cells

Abstract

This work proposes to compare the performances of solar cells with emitters made by using two different techniques. Bifacial diffusion using POCl3 precursor, commonly used in the PV industry, is compared to the single-sided spray-on diffusion annealed in an IR belt furnace. This technique is more suitable for obtaining higher throughput because of the possibility of using in-line processes associated with a reduced diffusion time. The use of solid doped sources can also simplify the development of alternative technologies, which often require localised or single-sided doping. Solar cells are fabricated following the standard industrial process on three different multi- crystalline materials. A similar current density was obtained for both types of emitter, which indicates a very similar bulk lifetime obtained at the end of the process. Nevertheless, a sharp decrease was observed in the fill factor and open-circuit voltage values with the spray diffused emitter. Dark I-V measurements and SunsVoc measurements indicated the presence of recombination inside the space-charge region resulting in a high value of saturation current density (J02). We conclude that this effect is due to the diffusion of impurities from the deposited film during the annealing stage.