Caballero, R.; Siebentritt, S.; Sakurai, K.; Kaufmann, C.A.; Lux-Steiner, M.Ch.: CGS-thin films solar cells on transparent back contact. In: 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion : Waikoloa, Hawaii, 7 - 12 May 2006Piscataway, NJ: IEEE Operations Center, 2006, p. 479-482
Abstract:
The goal of this work is to fabricate and study wide gap CuGaSe2 solar cells to be used as top cell of a mechanically stacked tandem device. CuGaSe2 (CGS) absorber thin films are prepared by co-evaporation in a-three stage process onto Mo soda-lime glass substrates and onto different transparent conductive oxides (TCOs): SnO2:F (FTO) and In2O3:Sn (ITO). Laser Light Scattering (LLS) is used as an in-situ process control. A deterioration of the transparency of the TCOs is observed after CGS deposition, especially for the ITO. The cell performance is lower for devices on TCOs due to the increased resistivity of the transparent back contact which leads to a decrease in fill factor (FF). The Cu-content during the process appears as a critical parameter to control the optical transmission as well as the efficiency of the device. Quantum efficiency measurements also reveals a smaller minority carrier collection for the solar cells grown on TCOs. A total area efficiency of 4.2 % for a device on FTO is achieved.