Film morphology is a key factor in determining device performance of small-molecule solar cells (SM-SCs). In self-assembly systems, the dipolar anchoring terminals can be used to fine-tune the morphology on a nanometer scale, but the mechanism of this control in solution-processed SM-SCs and its influence on device performance has remained largely unknown.

Chuanlang Zhan, Jiannian Yao, and colleagues, Institute of Chemistry, Chinese Academy of Sciences, Beijing, have systemically demonstrated that the stacking distance, phase size, and molecular orientation within thin films can be effectively controlled by engineering the dipolar anchoring terminals on the alkyl-chain spacer of a substituted diketopyrrolopyrrole-dithienylbenzodithiophene organic semiconductor. The team found that terminal ester groups are particularly suited to improving the photocurrent generation. These results indicate that the manipulation of dipolar anchoring terminals is an alternative method to molecular backbone design and alkyl-chain engineering to enhance device performance.

• Photocurrent Enhancement in Diketopyrrolopyrrole Solar Cells by Manipulating Dipolar Anchoring Terminals on Alkyl-Chain Spacer,
  Ailing Tang, Zhenhuan Lu, Shuming Bai, Jianhua Huang, Yuxia Chen, Prof. Qiang Shi, Prof. Chuanlang Zhan, and Prof. Jiannian Yao,
  Chem. Asian J. 2013.
  DOI: 10.1002/asia.201301416