Poly‐SiO_<i>x</i> Passivating Contacts with Plasma‐Assisted N₂O Oxidation of Silicon (PANO‐SiO_<i>x</i>)

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‐SiO x passivating contacts by combining plasma‐assisted N 2 O‐based oxidation of silicon (PANO‐SiO x ) with a thin film of phosphorus (n + ) or boron (p + )‐doped hydrogenated amorphous silicon oxide (a‐SiO x :H) are manufactured. Postannealing is conducted for transitioning a‐SiO x :H into poly‐SiO x . 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‐SiO x thickness and its passivation quality can be controlled. A higher SiO 2 content is observed in PANO‐SiO x than in the nitric acid oxidation of silicon (NAOS‐SiO x ) counterpart. PANO‐SiO x acts as a stronger diffusion barrier for both boron and phosphorus atoms compared to NAOS‐SiO x , 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 SiO 2 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.