1. The Organic Photonics and Electronics Group, Department of Physics, Umeå University, SE-90187 Umeå, Sweden
2. Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
3. School of Mechanical Engineering, Dongguan University of Technology, Dongguan 523808, China
4. LunaLEC AB, Linnaeus Väg 24, SE-901 87 Umeå, Sweden