| Work Detail |
A research team made up of scientists from Italian module manufacturer 3Sun has tested new zirconium-doped indium oxide electrodes in commercial heterojunction solar modules. The new electrodes reportedly achieve the same performance as their indium tin oxide-based counterparts and pave the way for lower indium consumption in heterojunction products.
A European research group led by the Italian University of Catania has tested the use of indium oxide (In2O3) doped with zirconium (Zr) as a transparent conductive film in silicon heterojunction (HJT) solar cells. developed by module maker 3Sun, a unit of Italian energy company Enel.
“Reducing the use of indium can be achieved by decreasing the thickness of the transparent conductive oxide (TCO) films,” the researchers explain. “The main problem of a TCO with reduced thickness is related to the consequent increase in the resistance of the sheet. Therefore, the key point is the doping of indium oxide with impurities that can improve conductivity.”
The scientists tested the film in various configurations, with varying atomic concentrations of Zr and thicknesses. They decided to dope In2O3 with Zr, since it is a type III transition metal (TM) that can be realized with high mobility and carrier concentration.
All films in this experiment were deposited at room temperature and subjected to postdeposition heat treatment at 200 °C in air. “This makes the synthesis procedure compatible with industrial manufacturing processes and applications in flexible devices with polymeric substrates,” they highlighted.
Zirconium-doped indium oxide (IZrO) thin films were deposited in an area of ??4 cm × 4 cm. While the standard value of thin film in commercial crystalline silicon solar cells is usually 100 nm, in the first experiment, IZrO was 40 nm thick. At the same time, the Zr content ranged from 0.6 at.% to 0.9 at.%.
With a Zr atomic concentration of 0.6%, films with different thicknesses of 15 nm, 40 nm, and 90 nm were created. “The thinnest 15nm film was compared with other ultrathin TCO films (ITO-20nm and AZO-20nm) showing the lowest sheet resistance,” the academics note.
Lastly, the group tested the IZrO electrodes on Suns cells. They used 90 nm IZrO films as front and back contacts of silicon bifacial HJT devices. The performance of the IZrO electrodes was “comparable” to that of their standard indium tin oxide-based counterparts.
“These results suggest that ultrathin IZrO films can be successfully used to reduce the costs and amount of indium used in indium-based transparent conductive oxide layers for solar cells,” the research group stated. |
