Ternary behavior and systematic nanoscale manipulation of domain structures in P3HT/PCBM/P3HT-b-PEO films
- ORNL
Nanophase separation plays a critical role in the performance of donor-acceptor based organic photovoltaic (OPV) devices. Although post-fabrication annealing is often used to enhance OPV efficiency, the ability to exert precise control over phase separated domains and connectivity remains elusive. In this work, we use a diblock copolymer to systematically manipulate the domain sizes of an organic solar cell active layer at the nanoscale. More specifically, a poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-b-PEO) diblock copolymer with a low polydispersity index (PDI = 1.3) is added to a binary blend of P3HT and 6,6-phenyl C{sub 61}-butyric acid methyl ester (PCBM) at different concentrations (0-20 wt%). Energy-filtered TEM (EFTEM) results suggest systematic changes of P3HT distribution as a function of block copolymer compatibilizer concentration and thermal annealing. X-ray scattering and microscopy techniques are used to show that prior to annealing, active layer domain sizes do not change substantially as compatibilizer is added; however after thermal annealing, the domain sizes are significantly reduced as the amount of P3HT-b-PEO compatibilizer increases. The impact of compatibilizer is further rationalized through quantum density functional theory calculations. Overall, this work demonstrates the possibility of block copolymers to systematically manipulate the nanoscale domain-structure of blends used for organic photovoltaic devices. If coupled with efficient charge transport and collection (through judicious choice of block copolymer type and composition), this approach may contribute to further optimization of OPV devices.
- Research Organization:
- Oak Ridge National Laboratory (ORNL); Center for Nanophase Materials Sciences
- Sponsoring Organization:
- SC USDOE - Office of Science (SC)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1043304
- Journal Information:
- Journal of Materials Chemistry, Journal Name: Journal of Materials Chemistry Journal Issue: 26 Vol. 22; ISSN JMACEP; ISSN 0959-9428
- Country of Publication:
- United States
- Language:
- English
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