1. Institute of Polymer Optoelectronic Materials and Devices; State Key Laboratory of Luminescent Materials and Devices; South China University of Technology; 381 Wushan Road Guangzhou 510640 China
2. Advanced Light Source; Lawrence Berkeley National Lab; Berkeley CA 94720 USA
3. Materials Sciences Division; Lawrence Berkeley National Lab; Berkeley CA 94720 USA
4. Polymer Science and Engineering Department; University of Massachusetts; Amherst MA 01003 USA