Ultra-thin nanocrystalline n-type silicon oxide front contact layers for rear-emitter silicon heterojunction solar cells

Hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) films have demonstrated a unique combination of low parasitic absorption and high conductivity. Here, we report on the use of n-type nc-SiOx:H as front surface field (FSF) in rear-emitter silicon heterojunction (SHJ) solar cells exhibiting excellent electrical cell parameters at a thickness down to only 5 nm. Using a seed layer, we are able to maintain excellent electrical performance (high fill factor (FF) and open circuit voltage (VOC)), while enhancing layer transparency for maximizing short circuit current (JSC). These results, together with the short deposition time (< 100 s), make the (n)nc-SiOx:H FSF attractive for reducing production costs in industrial applications. The best device, with the optimized (n)nc-SiOx:H FSF layer, shows VOC of 731 mV, FF of 80.6%, JSC of 38.3 mA/cm2 and a power conversion efficiency of 22.6%.