Spatially Resolving Ordered and Disordered Conformers and Photocurrent Generation in Intercalated Conjugated Polymer/Fullerene Blend Solar Cells
Open Access
- 25 July 2014
- journal article
- research article
- Published by American Chemical Society (ACS) in Chemistry of Materials
- Vol. 26 (15), 4395-4404
- https://doi.org/10.1021/cm501252y
Abstract
Resonance Raman spectroscopy was used to identify ordered and disordered conformers of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) blended with the electron acceptor [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in bulk heterojunction (BHJ) solar cells where PCBM intercalates into PBTTT side groups. We show that the PBTTT thiophene ring symmetric C=C stretching mode consists of contributions from ordered (ℏωC=C = 1489 cm-1, fwhm ∼ 15 cm-1) and disordered (ℏωC=C = 1500 cm-1, fwhm ∼ 25 cm-1) components and their relative amounts are sensitive to PCBM loading, annealing and excitation energy. The 1500 cm-1 PBTTT component originates from twisted thiophene rings and disordered side groups due to PCBM intercalation in a mixed kinetic phase and thermal annealing promotes ordering of PBTTT chains from the formation of bimolecular PBTTT/PCBM crystals. Density functional theory (DFT) Raman simulations of PBTTT monomers support these assignments. Resonance Raman images of annealed PBTTT/PCBM model solar cells confirm that ordered PBTTT chains are most concentrated in PCBM-rich bimolecular crystals and corresponding intensity modulated photocurrent spectroscopy (IMPS) and imaging measurements show increased nongeminate charge recombination at the boundaries of ordered/disordered regions.Keywords
Funding Information
- NIH Office of the Director (IIA-1301346)
- Division of Chemistry (CHE-0955242)
This publication has 50 references indexed in Scilit:
- Characterization of Charge-Carrier Transport in Semicrystalline Polymers: Electronic Couplings, Site Energies, and Charge-Carrier Dynamics in Poly(bithiophene-alt-thienothiophene) [PBTTT]The Journal of Physical Chemistry C, 2013
- Factors Governing Intercalation of Fullerenes and Other Small Molecules Between the Side Chains of Semiconducting Polymers Used in Solar CellsAdvanced Energy Materials, 2012
- Three-Dimensional Packing Structure and Electronic Properties of Biaxially Oriented Poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) FilmsJournal of the American Chemical Society, 2012
- Molecular Packing and Solar Cell Performance in Blends of Polymers with a Bisadduct FullereneNano Letters, 2012
- The phase behavior of a polymer‐fullerene bulk heterojunction system that contains bimolecular crystalsJournal of Polymer Science Part B: Polymer Physics, 2011
- Understanding Morphology-Dependent Polymer Aggregation Properties and Photocurrent Generation in Polythiophene/Fullerene Solar Cells of Variable CompositionsThe Journal of Physical Chemistry C, 2010
- Photoinduced Charge Carrier Generation in Blends of Poly(Thienothiophene) Derivatives and [6,6]-Phenyl-C61-butyric Acid Methyl Ester: Phase Segregation versus IntercalationThe Journal of Physical Chemistry C, 2010
- Role of Intermolecular Coupling in the Photophysics of Disordered Organic Semiconductors: Aggregate Emission in Regioregular PolythiophenePhysical Review Letters, 2007
- Raman Dispersion and Intermolecular Interactions in Unsubstituted Thiophene OligomersThe Journal of Physical Chemistry B, 2007
- Methods of Representing Emission, Excitation, and Photoconductivity SpectraJournal of the Optical Society of America, 1969