Small molecule sensitizers for near-infrared absorption in polymer bulk heterojunction solar cells

A low band gap small molecule chromophore has been incorporated into a polymer/fullerene bulk heterojunction (BHJ) solar cell yielding increased carrier generation in the near infrared and increased overall short circuit current. The use of a small concentration of a soluble oligothiophene with a diketopyrrolopyrrole core can extend the absorption and photocurrent of poly(3-hexyl thiophene):[6,6]-phenyl C-71 butyric acid methyl ester solar cells to 800 nm. Photocurrent from the dye embedded within the polymer BHJ is demonstrated, and the use of soluble small molecule sensitizers as a path toward high efficiency solar cells is discussed. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3001802].