[1] South China Univ Technol, Inst Polymer Optoelect Mat & Devices, State Key Lab Luminescent Mat & Devices, Guangzhou 510640, Guangdong, Peoples R China
[2] Shanghai Jiao Tong Univ, Dept Phys & Astron, Shanghai 200240, Peoples R China
[3] Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA
[4] Univ Massachusetts, Dept Polymer Sci & Engn, Amherst, MA 01003 USA