Speaker
Mr
Kedar Deshmukh
(Monash University)
Description
The microstructure and device physics of photovoltaic polymer blends based on the donor polymer BFS4 (a dithienyl-benzo[1,2- b:4,5-b]dithiophene / 5-fluoro-2,1,3-benzothiadiazole co-polymer) paired with the naphthalene diimide-based acceptor polymer P(NDI2OD-T2) will be presented. Efficiencies of over 4% are demonstrated, with an open circuit voltage of greater than 0.9 V achieved. Near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy and atomic force microscopy (AFM) measurements reveal that the top surface of BFS4:P(NDI2OD-T2) blends is covered with a pure BFS4 capping layer. XPS Depth profiling measurements confirm this vertical phase separation with a surface-directed spinodal decomposition wave observed. Grazing-incidence wide-angle x-ray scattering (GIWAXS) measurements confirm that BFS4 and P(NDI2OD-T2) are semicrystalline with both polymers retaining their semicrystalline nature when blended. Transmission electron microscopy reveals a relatively coarse phase-separated morphology, with elongated domains up to 200 nm in width. Photoluminescence spectroscopy reveals incomplete photoluminescence quenching with as much as 30% of excitons failing to reach a donor/acceptor interface Addition of DIO as solvent improves the fill factor of the devices from 0.46 to 0.54, thus improving the overall efficiency from 3.9% to 4.5%. Effect of addition of DIO in the neat polymers and blends is also studied using NEXAFS and GIWAXS techniques. NEXAFS and GIWAXS measurements were performed at the Australian Synchrotron, Soft X-ray and SAXS/WAXS beamlines respectively.
| Keywords or phrases (comma separated) | OPV, Morphology, GIWAXS, NEXAFS |
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Primary author
Mr
Kedar Deshmukh
(Monash University)
Co-authors
Dr
Amelia Liu
(MCEM)
Prof.
Christopher McNeill
(Monash University)
Dr
Eliot Gaan
(Australian Synchrotron)
Mr
Joseph Gallaher
(Victoria University of Wellington, NewZealand)
Prof.
Justin Hodgkiss
(Victoria University of Wellington)
Dr
Kane O'Donnell
(Curtin University, Bentley)
Dr
Lars Thomsen
(Australian Synchrotron)
Dr
Scott Watkins
(CSIRO)
Dr
Tianshi Qin
(CSIRO)
