A monolithic all-silicon multi-junction solar device for direct water splitting. (August 2016)

• Record Type: Journal Article
• Authors: Nordmann, S.; Berghoff, B.; Hessel, A.; Wilck, N.; Osullivan, B.; Debucquoy, M.; John, J.; Starschich, S.; Knoch, J.
• Is Part Of: Renewable energy. Volume 94(2016)
• Page Start: 90
• Page End: 95
• Publication Date: 2016-08
• Subjects: Monolithic -- Silicon -- Multi-junction -- Solar water-splitting -- Photovoltaic electrolysis (PV-E); Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2016.03.050
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: We present a silicon-based, monolithic multi-junction solar device that is suitable for the sustainable and reliable production of hydrogen. It is based on an interdigitated back-contact (IBC) solar cell which is modified, so that the p- and n-regions are connected in a combination of series and parallel connections, which triples the photovoltage compared to a single-junction cell. Thus, it provides a potential larger than the water redox potential of 1.23 V plus over-potentials at the electrodes. We fabricated a working demonstrator with an open-circuit voltage of 1.81 V and a short-circuit current density of 12.2 mA/cm 2 . The processing can be integrated in an existing IBC cell line with one additional fabrication step and a modified contact layout. Coupled to a 1 M H2 SO4 electrolysis system, with Pt and RuO2 electrodes, our device shows a solar-to-hydrogen conversion efficiency of 8%. In contrast to existing solutions, which are based on external series connections, it does not suffer from ohmic losses and holds the potential to reach 16.6%. Highlights: The concept of a monolithic, multi-junction PV-E device, based on high efficient, silicon, IBC solar cells is presented. A working demonstrator with 8% STH efficiency is fabricated and a detailed loss analysis is performed. The potential for more than 16% STH is deduced. 10% STH could be achieved at a total over-potential of 670 mV.