1. School of Pure and Applied Physics, Mahatma Gandhi University, Priyadarsini Hills P O, Kottayam-686560, India
2. School of Energy Materials, Mahatma Gandhi University, Priyadarsini Hills P O, Kottayam-686560, India
3. Institut Lumière Matière UMR 5306, Univ Lyon, Université Claude Bernard Lyon 1, CNRS, F-69100 Villeurbanne, France