Comparison of selenophene and thienothiophene incorporation into pentacyclic lactam-based conjugated polymers for organic solar cells
2015 (English)In: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, no 42, 7402-7409 p.Article in journal (Refereed) Published
In this work, we compare the effect of incorporating selenophene versus thienothiophene spacers into pentacyclic lactam-based conjugated polymers for organic solar cells. The two cyclic lactam-based copolymers were obtained via a new synthetic method for the lactam moiety. Selenophene incorporation results in a broader and red-shifted optical absorption while retaining a deep highest occupied molecular orbital level, whereas thienothienophene incorporation results in a blue-shifted optical absorption. Additionally, grazing-incidence wide angle X-ray scattering data indicates edge- and face-on solid state order for the selenophene-based polymer as compared to the thienothiophene-based polymer, which orders predominantly edge-on with respect to the substrate. In polymer : PC71BM bulk heterojunction solar cells both materials show a similar open-circuit voltage of similar to 0.80-0.84 V, however the selenophene-based polymer displays a higher fill factor of similar to 0.70 vs. similar to 0.65. This is due to the partial face-on backbone orientation of the selenophene-based polymer, leading to a higher hole mobility, as confirmed by single-carrier diode measurements, and a concomitantly higher fill factor. Combined with improved spectral coverage of the selenophene-based polymer, as confirmed by quantum efficiency experiments, it offers a larger short-circuit current density of similar to 12 mA cm(-2). Despite the relatively low molecular weight of both materials, a very robust power conversion efficiency similar to 7% is achieved for the selenophene-based polymer, while the thienothiophene-based polymer demonstrates only a moderate maximum PCE of similar to 5.5%. Hence, the favorable effects of selenophene incorporation on the photovoltaic performance of pentacyclic lactam-based conjugated polymers are clearly demonstrated.
Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY , 2015. Vol. 6, no 42, 7402-7409 p.
IdentifiersURN: urn:nbn:se:liu:diva-122675DOI: 10.1039/c5py01245gISI: 000363214600007OAI: oai:DiVA.org:liu-122675DiVA: diva2:871674
Funding Agencies|Chalmers Areas of Advance Materials Science, Energy and Nanoscience and Nanotechnology; Swedish Research Council; Knut and Alice Wallenberg foundation; Swedish Energy Agency; South Australian government; NSF; NIH/NIGMS via NSF [DMR-1332208]2015-11-162015-11-132016-03-01