Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells
2014 (English)In: Journal of physical chemistry C, ISSN 1932-7455, Vol. 118, no 46, 26462-26470 p.Article in journal (Refereed) Published
The film morphology and device performance of planar heterojunction
solar cells based on the molecular donor material α-sexithiophene (6T) are investigated.
Planar heterojunctions of 6T with two different acceptor molecules, the C60 fullerene and
diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom
layer has been varied between room temperature and 100 °C for each acceptor. By means
of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular
orientation of 6T is influenced by the preparation conditions and that the 6T film
templates the growth of the subsequent acceptor layer. These structural changes are
accompanied by changes in the characteristic parameters of the corresponding
photovoltaic cells. This is most prominently observed as a shift of the open circuit
voltage (Voc): In the case of 6T/C60 heterojunctions, Voc decreases from 0.4 to 0.3 V,
approximately, if the growth temperature of 6T is increased from room temperature to 100
°C. By contrast, Voc increases from about 1.2 V to almost 1.4 V in the case of 6T/DIP solar
cells under the same conditions. We attribute these changes upon substrate heating to
increased recombination in the C60 case while an orientation dependent intermolecular coupling seems to change the origin of the photovoltaic gap in the DIP case.
Place, publisher, year, edition, pages
2014. Vol. 118, no 46, 26462-26470 p.
Condensed Matter Physics
Research subject Physics; Materials Science
IdentifiersURN: urn:nbn:se:kau:diva-35420DOI: 10.1021/jp506180kISI: 000345474000005OAI: oai:DiVA.org:kau-35420DiVA: diva2:797053
FunderGerman Research Foundation (DFG), SPP 1355Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
publication date: October 27, 20142015-03-222015-03-222016-06-08Bibliographically approved