1. Key Laboratory of LCR Materials and Devices of Yunnan Province, National Center for International Research on Photoelectric and Energy Materials, School of Materials and Energy, Yunnan University, Kunming 650091, P. R. China
2. School of Physics and Astronomy, Yunnan University, Kunming 650091, P. R. China
3. Department of Physics, Government College Women University, Sialkot 51310, Pakistan
4. Department of Chemistry, Fatima Jinnah Women University, The Mall, Rawalpindi 46000, Pakistan
5. Center for Micro & Nano Devices, Department of Physics, COMSATS University Islamabad, Park Road, Islamabad 44000, Pakistan
6. TASC Labs, IOM CNR, Area Science Park, Trieste 34149, Italy