1. College of Polymer Science and Engineering, Sichuan University, Chengdu 610065, P. R. China
2. Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, Norrköping SE-601 74, Sweden
3. RISE Research Institutes of Sweden, Digital Systems, Smart Hardware, Bio-, Organic and Printed Electronics, Norrköping 60233, Sweden
4. Division of Fibre Technology, Department of Fibre and Polymer Technology, School of Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden
5. Wallenberg Wood Science Centre, Department of Science and Technology, Linköping University, Norrköping SE-601 74, Sweden
6. Wallenberg Wood Science Centre, Department of Fibre and Polymer Technology, School of Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm SE-100 44, Sweden