Efficient photovoltaic energy conversion in tetracene-C60 based heterojunctions -: art. no. 243506

We report organic solar cells fabricated with small-molecule organic semiconductor tetracene/C-60 heterojunction as the photoactive layer. The external power conversion efficiency of the devices under AM 1.5 solar illumination at 100 mW/cm(2) (1 sun) is 2.3 +/- 0.5% with relatively high open-circuit voltage (Voc=0.58 +/- 0.06 V) compared to most of the other small-molecular donor-acceptor (D-A) heterojunction solar cells reported so far. Using atomic force microscopy and x-ray diffraction we found that tetracene thin films consist of submicron-sized grains with rough surface and well defined molecular order. Therefore, using high mobility polycrystalline tetracene thin films for D-A heterojunction devices dramatically increases area of tetracene and C-60 interface for exciton diffusion to reduce the recombination. (c) 2005 American Institute of Physics.