* Corresponding authors

^a Materials Research Institute and School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
E-mail: h.ye@qmul.ac.uk, w.gillin@qmul.ac.uk

^b State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun, P. R. China

^c Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China
E-mail: mafontune@sina.com.cn

^d Materials Research Institute and School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, UK
E-mail: p.b.wyatt@qmul.ac.uk