The Control of the Positions of Fullerene Acceptors Relative to Polymer Main Chains in Mixed BHJs and Its Effect on OPV Performance
Chao Wang a
a RIKEN Center for Emergent Matter Science
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of International Conference on Perovskite and Organic Photovoltaics and Optoelectronics (IPEROP19)
Kyōto-shi, Japan, 2019 January 27th - 29th
Organizers: Hideo Ohkita, Atsushi Wakamiya and Mohammad Nazeeruddin
Oral, Chao Wang, presentation 054
Publication date: 23rd October 2018

Precise control of the molecular arrangements at the donor/acceptor interfaces in mixed bulk heterojunctions (BHJs) remains challenging, despite its vital importance for achieving high efficiency in organic photovoltaics (OPVs). This study reveals that the patterns of linear and branched alkyl side chains on electron-donating/-accepting alternating copolymers (D-A copolymers) can control the positions of fullerene acceptor molecules around the polymer main chains in mixed BHJs. Two-dimensional 1H-13C heteronuclear correlation solid-state NMR (2D HETCOR SS-NMR) results show a clear difference in the location of fullerene molecule between the BHJ films for twin polymers BDTP-1 and BDTP-2. A copolymer (BDTP-1) with an electron-accepting unit positioned in close proximity to fullerene molecule shows higher OPV performance. This is the first report to clearly demonstrate the molecular arrangements at the donor/acceptor interface in mixed BHJs. Our polymer design offers precise control over the interfacial molecular structure, thereby paving the way for overcoming the current limitations of OPVs based on mixed BHJs.

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