Impacts of humidity and temperature on the performance of transparent conducting indium tin oxide and electrical interconnects for solar applications

The impact of humidity and temperature on indium doped tin oxide based transparent conducting oxide (TCO) and electrical interconnects were assessed under hot and humid conditions. A review of thin film photovoltaic (PV) literature has shown one major failure mode of cells/modules is associated with the ingress of water into modules in the field. Water contamination has been shown to degrade the performance of the TCO in addition to corroding interconnects and other conductive metals/materials associated with the module. Few interconnects have been tried traditionally however currently the industry needs an alternative to traditional bonding methods which is reliable and has lower manufacturing costs. In this work, the impact of varying TCO process parameters on the thin film stability is studied in a hot and humid environment. Electrically conducting pressure sensitive adhesives have been applied as interconnects which hold manufacturing advantages. The stability of laminated TCO and interconnects is studied under hot and humid conditions and an optimized TCO layer and interconnect structure is proposed for a laminated CIGS module. A method for evaluation of TCO, interconnect, lamination materials and processes have been established to support qualification for the use in CIGS manufacturing.