[1] Vilnius Univ, Inst Photon & Nanotechnol, Fac Phys, LT-10257 Vilnius, Lithuania
[2] Bowling Green State Univ, Dept Phys, Bowling Green, OH 43403 USA
[3] Calif Technol Ctr, Solar 1, Santa Clara, CA 95050 USA
[4] Adv Res, Solar 1, Perrysburg, OH 43551 USA
[5] Chem & Nanosci Ctr, Natl Renewable Energy Lab, Golden, CO 80401 USA