Open-Circuit Voltage in Organic Solar Cells: The Impacts of Donor Semicrystallinity and Coexistence of Multiple Interfacial Charge-Transfer Bands
Type
ArticleAuthors
Ngongang Ndjawa, Guy Olivier
Graham, Kenneth
Mollinger, Sonya
Wu, Di M.
Hanifi, David
Prasanna, Rohit
Rose, Bradley Daniel

Dey, Sukumar
Yu, Liyang
Bredas, Jean-Luc

McGehee, Michael D.
Salleo, Alberto
Amassian, Aram

KAUST Department
KAUST Solar Center (KSC)Laboratory for Computational and Theoretical Chemistry of Advanced Materials
Material Science and Engineering Program
Organic Electronics and Photovoltaics Group
Physical Science and Engineering (PSE) Division
Date
2017-01-16Online Publication Date
2017-01-16Print Publication Date
2017-06Permanent link to this record
http://hdl.handle.net/10754/623882
Metadata
Show full item recordAbstract
In organic solar cells (OSCs), the energy of the charge-transfer (CT) complexes at the donor-acceptor interface, E , determines the maximum open-circuit voltage (V ). 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 enormously. Yet, the question of how structural heterogeneities alter CT states and the V is seldom addressed systematically. In this work, we combine experimental measurements of vacuum-deposited rubrene/C 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 and V . 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 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 configurations and maximizes V .Citation
Ndjawa GON, Graham KR, Mollinger S, Wu DM, Hanifi D, et al. (2017) Open-Circuit Voltage in Organic Solar Cells: The Impacts of Donor Semicrystallinity and Coexistence of Multiple Interfacial Charge-Transfer Bands. Advanced Energy Materials: 1601995. Available: http://dx.doi.org/10.1002/aenm.201601995.Sponsors
The Office of Competitive Research Funds at the King Abdullah University of Science and Technology supported this work in part under the CRG-3 program (A.A. and J.-L.B.). J.-L.B. acknowledges support in part from the Office of Naval Research–Global under Award No. N62909-15-1-2003. This work was also supported in part by the ONR Award Nos. N00014-14-1-0580 and N00014-16-1-2520. Portions of this work were done at the Cornell High Energy Synchrotron Source (CHESS). G.O.N.N., K.R.G., M.D.M., and A.A. acknowledge the Office of Competitive Research Funds for a GRP-CF award. K.R.G. and A.A. acknowledge SABIC for a postdoctoral fellowship. A.A. acknowledges SABIC for the Career Development SABIC Chair. The authors thank Dr. Detlef-M. Smilgies for help with acquisition of GIWAXS data at CHESS. CHESS was supported by the NSF & NIH/NIGMS via NSF Award No. DMR-1332208. The authors also acknowledge Dr. Sean Ryno for helpful discussions. Figure 3 was updated on January 17, 2017 to remove a formatting error. The scientific content was not changed.Publisher
WileyJournal
Advanced Energy MaterialsAdditional Links
http://onlinelibrary.wiley.com/doi/10.1002/aenm.201601995/fullae974a485f413a2113503eed53cd6c53
10.1002/aenm.201601995