Plasma immersion ion implantation of boron for ribbon silicon solar cells

¹ InESS-CNRS-Univ. Strasbourg, France
² IBS, Peynier, France
³ Solarforce, Bourgoin-Jallieu, France
⁴ Université d’Aix-Marseille, Institut Fresnel, Marseille, France

^a e-mail: thomas.michel@ion-beam-services.fr

Received: 18 September 2012
Accepted: 5 April 2013
Published online: 10 September 2013

Abstract

In this work, we report for the first time on the solar cell fabrication on n-type silicon RST (for Ribbon on Sacrificial Template) using plasma immersion ion implantation. The experiments were also carried out on FZ silicon as a reference. Boron was implanted at energies from 10 to 15 kV and doses from 10¹⁵ to 10¹⁶ cm^-2, then activated by a thermal annealing in a conventional furnace at 900 and 950 °C for 30 min. The n⁺ region acting as a back surface field was achieved by phosphorus spin-coating. The frontside boron emitter was passivated either by applying a 10 nm deposited SiO_X plasma-enhanced chemical vapor deposition (PECVD) or with a 10 nm grown thermal oxide. The anti-reflection coating layer formed a 60 nm thick SiN_X layer. We show that energies less than 15 kV and doses around 5 × 10¹⁵ cm^-2 are appropriate to achieve open circuit voltage higher than 590 mV and efficiency around 16.7% on FZ-Si. The photovoltaic performances on ribbon silicon are so far limited by the bulk quality of the material and by the quality of the junction through the presence of silicon carbide precipitates at the surface. Nevertheless, we demonstrate that plasma immersion ion implantation is very promising for solar cell fabrication on ultrathin silicon wafers such as ribbons.