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Characterization of Silicon Oxides Formed by Light-Induced Anodisation for Silicon Solar Cell Surface Passivation Jie Cui1, Xi Wang1, Robert Opila1,2, Alison Lennon1 1 The University of New South Wales, Sydney 2052, Australia. 2 University of Delaware, Newark, DE 19716, U.S.A. ABSTRACT In this paper we report the properties of the anodic silicon dioxide film formed using light-induced anodisation (LIA) method and its potential to be used as surface passivation layer of p-type silicon surfaces of silicon solar cells. The high uniformity of the formed oxide is possibly due to the uniform drift of the positive charge carriers in the silicon to the surface being anodised. The oxide grows at higher rate than that in nitric acid, an oxide layer with thickness of 18 nm can be formed by anodising for 10 min with 15 V bias in 0.5 M sulphuric acid. After annealing in oxygen and then forming gas at 400 ºC for 30 min, an average effective carrier lifetime of 120 µs was measured by quasi-steady state photoluminance on 180 µm p-type 3-5 Ohm cm Cz silicon wafers, with a value of 110 µs being measured for the same wafers passivated by a thermally-grown oxide of the same thickness. The properties of the anodic silicon dioxide layers formed by LIA have been characterized by ellipsometry, x-ray photoelectron spectroscopy, quasi-steady state photoluminance and Fourier transform infrared spectroscopy.

INTRODUCTION The key driver for silicon photovoltaic (PV) technology development is now clearly cost, either represented as a cost per Watt of power produced or as a levelised cost of electricity generated. Recent significant reductions in manufacturing cost have been largely attributed to ‘economies-of-scale’ benefits, however maintaining the current PV downward cost trajectory will require innovations that reduce the cost per Watt of power produced by either directly reducing the cost of processing and/or by increasing the efficiency of devices manufactured [1]. In silicon solar cell manufacturing, a key step that can directly result in higher efficiencies by way of increased open circuit voltages is the passivation of the surface of silicon wafers. Thermally-grown silicon dioxide has been extensively used to passivate surfaces of silicon solar cells for many years. However the high temperature oxidation process requires critical wafer cleaning and a substantial thermal budget. Furthermore, the high temperatures required are often detrimental to lower-cost, lower purity silicon wafers [2] that are increasingly being used for photovoltaic applications in order to reduce manufacturing costs. Recently, surface recombination velocities of less than 40 cm/s have been demonstrated on silicon wafers passivated with silicon dioxide layers that were electrochemically grown in nitric acid at room temperature [3]. The performance of this silicon surface passivation is comparable to that attained by the best thermal oxide [4], however the electrochemical method reported in [3] resulted in slow growth, non-uniform oxidation and was sensitive to the