1. College of Materials Science and Engineering, Fuzhou University, Fujian 350108, China
2. Catalonia Institute for Energy Research−IREC, 08930 Sant Adrià de Besòs, Barcelona, Spain
3. Department of Electronic and Biomedical Engineering, Universitat de Barcelona, 08028 Barcelona, Spain
4. ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain