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HL: Fachverband Halbleiterphysik

HL 114: Oxides: Bulk, films and interfaces

HL 114.12: Vortrag

Freitag, 4. April 2014, 12:30–12:45, POT 251

Transparent photovoltaics: ZnO/NiO heterojunctions working as UV solar cells — •Robert Karsthof, Paul Räcke, Zhipeng Zhang, Holger von Wenckstern, and Marius Grundmann — Universität Leipzig, Insitut für Experimentelle Physik II, Linnéstraße 5, 04103 Leipzig, Germany

A solar cell transmitting visible light rather than absorbing it seems to contradict the general idea of efficient energy conversion. However, it has been shown recently [1] that a device which only absorbs photons from the IR and UV range of the solar spectrum can reach conversion efficiencies up to 37% (Shockley-Queisser limit). PV modules consisting of such cells could be used to generate electric power e.g. on large window areas on office buildings without reducing the daylight illumination of the interior – in contrast to conventional technologies.

In this work we present an approach based on zinc oxide-nickel oxide thin film heterojunctions. We grew p-type NiO by reactive DC and RF sputter deposition on top of pulsed laser deposited (PLD) n-type ZnO on a-sapphire to produce semi-transparent pn-junctions. A highly Al-doped PLD-grown ZnO layer was used as transparent back contact. The completed cell stack showed a high transmission of 50% and above. The cells were characterized by means of IV and external quantum efficiency (EQE) measurements. We could confirm that with this approach energy conversion efficiencies above 1% and EQE around 100% in the UV range are already feasible.
[1] R. Lunt: Appl. Phys. Lett. 101, 043902 (2012)