High mobility In2O3:H as contact layer for a-Si:H/c-Si heterojunction and μc-Si:H thin film solar cells

• Crystallinity of IOH has been monitored during annealing with energy dispersive XRD.
• ITO/IOH bilayers have been integrated into a-Si:H/c-Si solar cells.
• Jsc gains due to higher bilayer transparency have been simulated with OPAL.
• IOH films have been applied to μc-Si:H cells as silver-free back contact.

The crystallization process of hydrogen doped In2O3:H (IOH) films is investigated with energy-dispersive X-ray diffraction measurements. At annealing temperatures between 125 and 150 °C crystallization of 220 nm thin films occurs within only 2 min, and the percentage of the crystalline phase does not change anymore when the temperature is raised above the crystallization temperature of 150 °C. Maximum electron mobilities above 100 cm2/Vs have been reached after crystallization. The IOH films were integrated as front contact into amorphous/crystalline silicon heterojunction cells and compared to In2O3:Sn (ITO) front contacts. Cells with ITO/IOH bilayer front contacts show a slightly lower open circuit voltage because of the a-Si:H passivation layer degradation caused by the longer annealing process needed for the crystallization of the bilayers, while all cells reach total area efficiencies around 20%. IOH films were also implemented as silver free back contact for μc-Si:H cells, and show higher short-circuit current densities than ZnO:Al back contacts because of the higher near-infra-red transmission of IOH.