Poly‐SiOx Passivating Contacts with Plasma‐Assisted N2O Oxidation of Silicon (PANO‐SiOx)

Abstract

Passivating contacts are crucial for realizing high‐performance crystalline silicon solar cells. Herein, contact formation by plasma‐enhanced chemical vapor deposition (PECVD) followed by an annealing step is focused on. Poly‐SiOx passivating contacts by combining plasma‐assisted N2O‐based oxidation of silicon (PANO‐SiOx) with a thin film of phosphorus (n+) or boron (p+)‐doped hydrogenated amorphous silicon oxide (a‐SiOx:H) are manufactured. Postannealing is conducted for transitioning a‐SiOx:H into poly‐SiOx. The aim is to achieve a contact with low absorption and high‐quality passivation. It is demonstrated that by tuning the plasma oxidation process time and power, the PANO‐SiOx thickness and its passivation quality can be controlled. A higher SiO2 content is observed in PANO‐SiOx than in the nitric acid oxidation of silicon (NAOS‐SiOx) counterpart. PANO‐SiOx acts as a stronger diffusion barrier for both boron and phosphorus atoms compared to NAOS‐SiOx, affecting the dopant distribution during annealing. Implied open‐circuit voltages up to 751 and 710 mV for n+ and p+ flat symmetric samples, respectively, are demonstrated. With respect to standard thermally grown SiO2 tunneling oxide combined with (in/ex )situ‐doped low‐pressure chemical vapor deposition poly‐Si, this study presents a simple alternative for manufacturing passivating contact fully based on PECVD processes.