High Mobility Transparent Conductive Oxides for Silicon Heterojunction Solar Cells Deposited by Rotatable Magnetrons

35th European Photovoltaic Solar Energy Conference and Exhibition; 456-459
Sputtered indium tin oxide (ITO) is a widespread used material for application as transparent conducting oxide as the front contact of rear-junction silicon heterojunction solar cells. Standard ITO films suffer from too high parasitic absorption in both the short- and the long-wavelength range. The aim of this contribution is to investigate lower absorbing TCOs deposited with industrial DC sputtering from rotatable targets. High Voc values >735 mV demonstrate that in spite of the high-power industrial DC sputter process no significant sputter damage is observed, independent of the target material. Cell efficiencies up to 23.3% are obtained with titanium-doped (ITiO) and tin-doped indium oxide (ITO 99/1). The highest short circuit current values of 39.6 mA/cm2 are reached with an ultimately low-carrier and high-mobility indium-oxide-based material. The cell efficiency in this case, however, is over-compensated by a too low FF, mostly due to a higher contact resistivity and TCO sheet resistances. We ascribe this effect to the very low carrier concentration.