Fei Huang and colleagues, South China University of Technology, Guangzhou, China, improved the performance of inverted polymer solar cells (IPSCs) by introducing a rationally designed polymeric interlayer based on a conjugated metallopolymer with improved charge transport.
This new metallopolymer cathode interlayer is a Hg-containing derivative of amino-functionalized conjugated polymers (AFCPs), PFEN-Hg. It was synthesized and employed as an efficient interlayer for improving the electron transport and collection properties of high-performance IPSCs. The new polymer offers properties including orthogonal solvent processability, good film formation, effective high-work function (WF) modification of the indium-tin oxide (ITO) substrate, low optical absorption, good electron selectivity, and good electron transport properties.

The resulting devices exhibited significantly improved performance with power conversion efficiencies exceeding 9 %. These are among the best reported for single-junction PSCs. Moreover, good device performance was achievable over a wider range of film thickness. The team thinks this is likely due to the Hg−Hg interactions and improved π−π stacking.

• High-Efficiency Polymer Solar Cells via the Incorporation of an Amino-Functionalized Conjugated Metallopolymer as a Cathode Interlayer,
  Shengjian Liu, Kai Zhang, Junming Lu, Jie Zhang, Hin-Lap Yip, Fei Huang, Yong Cao,
  J. Am. Chem. Soc. 2013.
  DOI: 10.1021/ja408363c