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Open-Circuit Voltage in Organic Solar Cells: The Impacts of Donor Semicrystallinity and Coexistence of Multiple Interfacial Charge-Transfer Bands.
- Source :
- Advanced Energy Materials; 6/21/2017, Vol. 7 Issue 12, pn/a-N.PAG, 10p
- Publication Year :
- 2017
-
Abstract
- In organic solar cells (OSCs), the energy of the charge-transfer (CT) complexes at the donor-acceptor interface, E<subscript>CT</subscript>, determines the maximum open-circuit voltage ( V<subscript>OC</subscript>). The coexistence of phases with different degrees of order in the donor or the acceptor, as in blends of semi-crystalline donors and fullerenes in bulk heterojunction layers, influences the distribution of CT states and the V<subscript>OC</subscript> enormously. Yet, the question of how structural heterogeneities alter CT states and the V<subscript>OC</subscript> is seldom addressed systematically. In this work, we combine experimental measurements of vacuum-deposited rubrene/C<subscript>60</subscript> bilayer OSCs, with varying microstructure and texture, with density functional theory calculations to determine how relative molecular orientations and extents of structural order influence E<subscript>CT</subscript> and V<subscript>OC</subscript>. We find that varying the microstructure of rubrene gives rise to CT bands with varying energies. The CT band that originates from crystalline rubrene lies up to ≈0.4 eV lower in energy compared to the one that arises from amorphous rubrene. These low-lying CT states contribute strongly to V<subscript>OC</subscript> losses and result mainly from hole delocalization in aggregated rubrene. This work points to the importance of realizing interfacial structural control that prevents the formation of low E<subscript>CT</subscript> configurations and maximizes V<subscript>OC</subscript>. [ABSTRACT FROM AUTHOR]
- Subjects :
- OPEN-circuit voltage
SOLAR cells
ELECTRODE reactions
CHARGE transfer
HETEROGENEITY
Subjects
Details
- Language :
- English
- ISSN :
- 16146832
- Volume :
- 7
- Issue :
- 12
- Database :
- Complementary Index
- Journal :
- Advanced Energy Materials
- Publication Type :
- Academic Journal
- Accession number :
- 123715731
- Full Text :
- https://doi.org/10.1002/aenm.201601995