Work Package 4-T4.3 - July 2018

Objectives and Status


The front side electrodes of III-V solar cells comprise ofmetal grid lines on a patterned CAP. The task is to develop industrially scalable low cost processes for the front contact grid deposition suitable for tandem solar cells.


Reducing the total series resistance of electrodes (contact resistance and bulk-resistance):

  • Metal inks were applied as contacts on the surface of GaAs by inkjet printing and spin coating.
  • Two sintering methods (laser and reducing atmosphere) for metal NP inks were developed. With respect to environmental impact; laser sintering is so far a more promising process.
  • Ohmic contact behavior is observed in first results. Further activities to achieve an optimized contact resistance are ongoing.



Less than 2% of the front side area is shaded by electrodes.


  • Fine interdigitated structures of metal inks were deposited and sintered on the surface of n-GaAs. Further activities aim to optimize thickness and thin film homogeneity in order to achieve the required contact resistance.
  • The quality of printed structures was investigated using different methods such  as XPS/UPS, AFM, SEM, parametric analyzer and profilometer.
  • Selective etching of GaAs versus Au was successfully conducted, further investigations of selective etching with other electrode metals will be continued.



Task: Joanneum_Page_3.PNG

Development of bonding processes as an interconnection between top and bottom cells with high transparency and low contact resistance.

  • TCO thin films were spray-coated on highly doped Si and III-V epi layers and then annealed.
  • The quality of the applied TCO bonding films was investigated with electrical, mechanical (Maszara blade) and optical microscope characterization. Low resistance ohmic contact can be achieved for Si substrates. A high transmission is realized for the demanded wavelengths in general.
  • With respect to mechanical stability, a high bond strength is observed. Further investigations will focus on improving the contact resistance on III-V materials as well as on bond homogeneity.