Study of direct PECVD SiNx-induced surface emitter and bulk defect passivation in p-type silicon solar cells

This paper shows that direct low-frequency (LF) deposition of SiN films at 425 °C by PECVD followed by a conventional screen-printed contact firing cycle is more effective than a high-frequency (HF) SiN film deposited at 300 °C in passivating both bulk defects and the emitter surface. The emitter saturation current density (J_oe), was found to be higher for LF SiN compared to the HF SiN just after deposition. J_oe values for LF SiN reduced dramatically after contact firing to 100-200 fA/cm², well below the J_oe for HF SiN passivated emitters. Solar cells fabricated on float zone (FZ) Si and mc-Si grown by the heat exchanger method (HEM) yielded efficiencies as high as 17.2% and 16.8%, respectively, when coated with LF SiN. The enhanced cell performance is corroborated by a higher short wavelength IQE response in FZ and HEM cells and a higher post hydrogenation lifetime in HEM mc-Si cells coated with LF SiN.