Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 8: Poster: Organic Semiconductors

CPP 8.22: Poster

Montag, 14. März 2011, 17:30–19:30, P2

The role of molecular design for optimized morphology in organic solar cells — •Christoph Schuenemann, Joerg Alex, Jan Meiss, Wolfgang Tress, Karl Leo, and Moritz Riede — IAPP, TU Dresden

Diindenoperylene (DIP) is a well known organic semiconductor which is also an attractive absorber material for applications in small molecule organic solar cells. We have synthesized Ph4-DIP, a new derivative, consisting of the DIP core and four phenyl rings attached to the two indeno-groups. To compare these two similar molecules, DIP and Ph4-DIP, we characterize the morphology of thermally evaporated thin films using x-ray diffraction and atomic force microscopy. Pristine films and mixed layers with C60 (1:1 by volume) relevant for bulk heterojunction solar cells are deposited at different substrate temperatures. Whereas DIP forms highly crystalline pristine and DIP:C60 blend layers, Ph4-DIP is found to grow amorphous even at substrate temperatures of 110°C in pristine and Ph4-DIP:C60 blend layers. These results highlight the strong influence of the molecular design on the molecular arrangement in organic thin films. The stacking of the Ph4-DIP molecules is disturbed by the four phenyl rings that are tilted with respect to the flat DIP core. The DIP molecules without these phenyl rings, however, are able to stack very densely and form large crystallites. These morphological differences can explain the diverse performance of organic solar cells made from DIP and Ph4-DIP due to different exciton diffusion length and charge carrier mobilities.