Study of Direct PECVD SiN(x)-Induced Surface Emitter and Bulk Defect Passivation in P-Type Silicon Solar Cells
Upadhyaya, A. D.
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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 (Joe), was found to be higher for LF SiN compared to the HF SiN just after deposition. Joe values for LF SiN reduced dramatically after contact firing to 100-200 fA/cm(2), well below the Joe 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.