Evaluating the contact properties of transparent conductive oxides on crystalline silicon homojunction solar cells

The interest of using Transparent Conductive Oxides (TCO's) as alternative contact layers on crystalline silicon (c-Si) homojunction solar cells is discussed in this paper. To evaluate the contact quality, vertical conductivity as well as passivation properties have been measured on symmetrical test structures showing either n+ or p+ surface doping, covered with an Indium Tin Oxide (ITO) layer deposited by sputtering. The influence of annealing steps between 200°C and 700°C on the TCO/c-Si and Metal/TCO contact properties are shown. Using a direct TCO contact on both sides, an efficiency of 15.4% is obtained on 156×156 mm
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n-type solar cells, limited by the high saturation current density of the ITO contact. To avoid recombinations at the TCO/c-Si interface, another deposition method for the TCO (with lower surface damage) should be used.