Low-temperature rear surface passivation schemes for >20% efficient silicon solar cells

Abstract

Results of different types of crystalline silicon solar cells passivated using low-temperature plasma-enhanced chemical vapour deposited (PECVD) films of amorphous silicon (a-Si:H) and silicon nitride (SiN/sub x/) are presented. The SiN/sub x/ films are deposited at 400/spl deg/C and the a-Si:H films at 225/spl deg/C, respectively. An independently confirmed efficiency of 20.6% is achieved for SiN/sub x/-passivated cells with an additional local back surface field (LBSF) underneath the rear metalised area. The LBSF reduces carrier recombination at the metal contacts and avoids parasitic shunting between the induced inversion layer underneath the SiN/sub x/ films and the rear contact lines. Furthermore, it is shown that a-Si:H films provide an excellent surface passivation without inducing an inversion layer. Efficiencies of 19.2% are reported for solar cells with a-Si:H rear surface passivation. Open-circuit voltages in excess of 650 mV demonstrate that efficiencies >20% are well achievable for a-Si:H rear surface passivated solar cells.