Optimisation of ITO by excimer laser annealing for a-Si:H/c-Si solar cells

The role of transparent conducting oxides (TCO) on the front side of amorphous/crystalline (c-Si) silicon heterojunction solar cells (HJ) is of great importance for high efficiency solar cells. They have to fulfil high transparency and high electrical conductivity. Then, device performance can be increased if an appropriate front side scheme is incorporated into the cell device because of a direct impact either on short-circuit current (J(SC)) and fill factor (FF). Indium Tin Oxide (ITO) has demonstrated to be a very good candidate to get the best optical/electrical compromise: low resistivity values can be achieved thanks to relatively high free carrier concentration (N-d > 2.10(20) cm(-3)), though absorption in the IR range is still a limiting factor for high JSC devices. In this work, we introduce the laser treatments of ITO by Excimer laser annealing (ELA) as an interesting approach to improve the optical/electrical compromise of the material. First, we have studied the changes in material properties when irradiating with different laser conditions. Then, we have looked at the effect of these laser treatments on the passivation properties of HJ precursors. Finally, complete HJ solar cells have been fabricated with laser annealed ITOs at optimal conditions. (C) 2012 Published by Elsevier Ltd. Selection and peer-review under responsibility of the scientific committee of the SiliconPV 2012 conference.