1. Department of Electrical and Computer Engineering, Georgia Institute of Technology 1 , Atlanta, Georgia 30332, USA
2. Center for Advanced Electronics and Photovoltaic Engineering, International Islamic University Islamabad 2 , Islamabad, Pakistan
3. Department of Chemistry and Biochemistry, University of South Carolina 3 , Columbia, South Carolina 29208, USA
4. Department of Electrical Engineering, University of South Carolina 4 , Columbia, South Carolina 29208, USA