1. Organic Electronics Laboratory, Department of Physics, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
2. Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
3. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
4. Saha Institute of Nuclear Physics, HBNI, 1/AF Bidhannagar, Kolkata 700 064, India
5. School of Nanoscience and Technology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India