The Sino-Danish joint research between two Danish Universities, namely the Technical University of Denmark (DTU), and Aalborg University (AAU), was initiated in 2009. Such two teams have built up effective and solid collaboration in respects to solar cell materials and device fabrication. Students exchange program plays an important role in such co-operations. In AAU, part of our work was carried out with series of donor-acceptor low band gap polymers composed of alternating dithienopyrrole or its derivative as donors and phthalimide or thieno[3,4-c]pyrrole-4,6-dione as acceptors are synthesized by Stille coupling polymerization. All polymers show strong absorption in the visible region, for polymers possessing thieno[3,4-c]pyrrole-4,6-dione as an acceptor, their film absorption covers the region of 500-800 nm and 500-750 nm respectively, which makes them attractive as low band gap polymer solar cell (PSC) materials. With the incorporation of thiophene bridges, thieno[3,4-c]pyrrole-4,6-dione containing products have 0.24 and 0.21 eV higher HOMO energy levels than phthalimide polymers, respectively. A band gap as low as 1.66 eV is obtained for one of the polymers.An up-scaling experiment is performed as bulk-heterojunction PSCs with an inverted device geometry with an inverted device geometry fabricated on small scale by spin coating and on large scale using roll-to-roll (R2R) slot-die coating and screen printing, which are relative better performance than a standard P3HT/PCBM driven device.

Donghong Yu obtained his Ph.D. degree in Polymer Chemistry and Physics at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, China, in 1997. From 1998 to 2000, he worked as a postdoctoral research fellow in National Institute of Materials and Chemical Research, Tsukuba, Japan, then moved to Aalborg University, Denmark, being a postdoc until 2001. He was appointed as an Assistant Professor at Aalborg University in 2001, and Associate Professor in 2006. Currently he is focusing on syntheses of conjugated polymers/small molecules as either donor or acceptor materials for organic solar cells.