[1] Australian Natl Univ, Dept Elect Mat Engn, Res Sch Phys Sci & Engn, Canberra, ACT 0200, Australia
[2] Australian Natl Univ, Ctr Sustainable Energy Syst, Fac Engn & Informat Technol, Canberra, ACT 0200, Australia
[3] CNR, Ist Struttura Mat, Unita Staccata Trieste Basovizza, I-34012 Trieste, Italy