Passivation of Plasma Oxidized SiOX Layer Using Field Effect on p-type Emitter Surface for High Efficiency c-Si Solar Cell Application

The surface passivation is one of the crucial steps to achieve high conversion efficiencies in c-Si solar cells. A thermally stable thin film with a negative charge (for p-type surface) passivation layer is required to develop a good front passivation suitable for n-type c-Si solar cells. Silicon suboxide (SiOSUBX/SUBSUB/SUB) layer using PECVD provides a good passivation layer which has low temperature process and charge control in thin-film layer. In this paper, a PECVD stack layer consisting of SiOSUBX/SUB and SiNSUBX/SUB was employed for front side passivation. The optimal refractive index of SiOSUBX/SUB and SiNSUBX/SUB were found by varying the silane (SiH₄), ammonia (NH3) and nitrous oxide (N₂O) gas ratio for decrease optical loss. -1.71 × 10SUP11/SUPcmSUP-2/SUP of negative charge (Qf) and 5×10SUP10/SUP cmSUP-2/SUP eVSUP-1/SUP of DSUBit/SUB (interface trap density) were obtained at 10 nm thick SiOSUBX/SUB thin-film. With this optimized SiOx/SiNx stack layer on p+ surface wafer using PECVD, the effective lifetime of 280 ㎲ and implied VOC of 690 mV were achieved. It is expected that the efficiency of the n-type silicon solar cell can be improved by applying the optimized SiOx condition to the front passivation layer.