1. Department of Advanced Materials Engineering, Daejeon University, 62 Daehak-ro, Dong-gu, Daejeon 34520, Korea
2. Department of Physics, Kunsan National University, 558 Daehak-ro, Gunsan 54150, Korea
3. Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
4. Department of Chemistry, Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
5. Thermoelectric Conversion Research Center (TCRC), Creative and Fundamental Research Division, Korea Electrotechnology Research Institute (KERI), 10-12 Bulmosan-ro, Changwon 51543, Korea