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Ion Implanted Dielectric Films for an Improved Optical and Electronic Silicon Photovoltaic Response Avi Shalav1,2, Christian Henderson1,2, Tom Ratcliff2 and Andrew Thomson2 1

Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia 2

School of Engineering, College of Engineering and Computer Science, Australian National University, ACT 0200, Australia ABSTRACT Over the past few years, ion implanters specifically developed for the high throughput required by the silicon photovoltaic industry, have become commercially available. Recent research and development has focused on the formation of doped surface regions, particularly the formation of selective emitters. In this study we explore two effects of ion implantation into a thermal silicon dioxide passivating/antireflection dielectric. We show evidence that the electronic and optical performance of the layer can be improved via the incorporation of charges created within the dielectric film and the creation of a graded refractive index, minimizing the surface recombination and reflection losses respectively. INTRODUCTION Ion implantation offers superior single sided process control and repeatability of the dopant profile, junction depth and carrier concentration required for modern day microelectronic circuits. Although promising results were obtained in the 1950’s for photovoltaic (PV) applications, the technique has been too expensive for the large area, high throughput required to be commercially viable. Recently, commercial ion implanters, with a high wafer throughput, have been specifically developed and commercialized for the PV industry and an aggressive resurgence into the progress of ion implantation for silicon solar cell applications has ensued [1]. Although recent research and development has focused primarily on selective emitter formation, the technique could also be used for additional advanced electronic and optical concepts resulting in an enhanced PV performance. For example, ion implantation offers an additional method to directly create or inject charges into the passivating dielectric film(s) [2] and manipulate the refractive index via damage or stoichiometric changes [3]. Heavily-doped silicon surface regions, which in high-efficiency devices are, are at the n+ and p contact, manipulate the balance between the populations of electrons and holes resulting in lower effective recombination velocities. As silicon solar cells become more efficient, and potentially more cost effective by becoming thinner, surface passivation becomes particularly important. Another method to achieve this, which can be superior to the highly doped regions, is to utilize an electrostatically charged dielectric layer. The action of the dielectric is two-fold. Firstly, it provides atoms such as oxygen and hydrogen that chemically bond to the silicon atoms at the surface, thus reducing drastically the density of unsatisfied, dangling bonds and hence the +

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