Influence of SiO2 nanosphere on the performance of n+ layer fabricated by phosphorus diffusion using phosphoric acid solution

Phosphorus diffusion was used widely in mass production of p-type silicon solar cells. In order to improve the quality of P doped layer fabricated, a novel phosphorus source mixing phosphoric acid with SiO2 nanosphere was introduced. A high diffusion uniformity of 94.9% was obtained when SiO2 nanosphere was introduced while the uniformity of sample diffused without SiO2 nanosphere was 84.49%. It was found that the formation of dead layer could be avoided by introducing the SiO2 nanosphere, as observed by SEM images, and the minority carrier lifetime of sample was enhanced by 27.87 µs. The surface sheet resistance decreased from 132.62 to 12.8 Ω/□ with the increase of temperature from 825 to 925 °C. Through an etching method, a variation of junction depth increasing from 300 to 571 nm was found with increasing temperature. The variation trends of surface sheet resistance and junction depth with the increase of time were similar with that of temperature.