1. Department of Semiconductor Optoelectronics, Institute of Materials Science and Applied Research, Vilnius University, Sauletekio ave. 9 bld. 3, 10222 Vilnius, Lithuania
2. Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
3. Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), 33608, Pessac, France