Progress on Energy Selective Contacts for Hot Carrier Solar Cells at UNSW

  • Santosh Shrestha, ARC Photovoltaic Centre of Excellence, University of New South Wales, Australia
  • Gavin Conibeer, ARC Photovoltaic Centre of Excellence, University of New South Wales, Australia
  • Yasuhiko Takeda, Toyota Central Research and Development Laboratories, Inc., Japan
  • Tadashi Ito, Toyota Central Research and Development Laboratories, Inc., Japan

    • Hot Carrier solar cells are promising third generation photovoltaic devices. One of the important requirements of HC solar cells is the extraction of ‘hot’ carriers within a narrow range of energies with Energy Selective Contacts (ESCs) so that only a small fraction of their excess energy above the band edge is lost when the hot carriers comes in contact with the cold carriers in the metal electrodes.

    In this paper we present progress on the fabrication and characterisation of ESCs at UNSW. Double barrier resonant tunnelling devices consisting SiO2/Si QD/SiO2 layers have been fabricated for ESCs by RF magnetron sputtering using quartz and silicon targets followed by high temperature annealing.

    Electrical characterisation has shown the evidence of negative differential resistance (NDR) for these types of structures. Results of an I-V measurement on a typical resonant tunnelling device are shown in Fig. 1. Here, the black and the red data points are results of two subsequent measurements on a device with an interval of few minutes. In both I-V profiles, NDR resonance can be observed. This demonstrates that NDR characteristic is repeatable. Similar results have been observed for other similar devices. However, further work is required to improve the quality factor of the resonance (ratio of peak height to peak width).