At the front contact of thin film silicon solar cells, the junction between the p-doped window layer and the n-type transparent electrode results in a barrier that must be surmounted by the charge carriers. The barrier height is governed by the work function difference of these two materials. For different compositions of the well known In2O3-SnO2 (ITO) system, we find that higher oxygen partial pressure during sputter deposition increases the work function of the deposited films. Over the same range of oxygen partial pressures, ITO electrodes with low tin content applied to n-i-p type thin film silicon solar yield a gain in Voc by up to 40 mV. *