Study of hydrogen influence and conduction mechanism of amorphous indium tin oxide for heterojunction silicon wafer solar cells

The optoelectrical properties of the indium tin oxide (ITO) films are investigated at low-power and low-temperature conditions for heterojunction silicon wafer solar cell applications. ITO films deposited at 100W in hydrogen-diluted argon ambient have the best optoelectrical quality, giving transparent and conductive (carrier mobilities in the 50-60cm(2)/Vs range) films. X-ray diffraction analysis shows that the ITO films deposited at 100W are primarily of amorphous (or quasi-amorphous) nature, regardless of the deposition conditions. Based on several other characterisation methods, it is found that the high electron mobility achieved by the hydrogenated ITO films is mainly due to the reduction of scattering centres. A few In2O3 samples are prepared at similar deposition conditions to investigate the electrical conduction mechanism of ITO films. Due to the low doping efficiency of tin atoms in amorphous ITO, the main source of the free electron charge carriers are the oxygen vacancies.