Influence of PECVD deposition temperature on phosphorus doped poly-silicon passivating contacts

Abstract

This paper describes the influence of plasma enhanced chemical vapor deposition (PECVD) deposition temperature on heavily doped silicon based (doped-Si/SiOx) passivating contacts for silicon solar cells. The doped-Si films are obtained by PECVD intrinsic amorphous silicon (a-Si) and a subsequent thermal POCl3 diffusion process. By changing the deposition temperature of PECVD, a-Si films with different degrees of crystallinity and density can be obtained. These differences between the a-Si films result in different properties of the passivating contacts in terms of passivation quality and carrier selectivity. By exploring a range of PECVD deposition temperatures from 250 °C to 470 °C, the best passivation quality is obtained at a temperature of 420 °C. On the other hand, the contact resistivity decreases with increasing deposition temperature. After studying the a-Si properties and the resulting passivating contact properties, we obtain optimal passivating contacts with a high implied open-circuit voltage (iVoc) of 742 mV and a low contact resistivity ρc of 6.4 mΩ∙cm2.