Conjugated Block Copolymers In Organic Photovoltaics

Open Access
Witman, Matthew David
Area of Honors:
Chemical Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Enrique Daniel Gomez, Thesis Supervisor
  • Darrell Velegol, Honors Advisor
  • self-assembly
  • organic solar cells
  • all-conjugated block copolymers
Organic semiconductors for photovoltaic devices represent the next generation of solar cell technology. Yet limitations including weak intermolecular interactions, disorder at semiconductor interfaces, and lack of control over the active layer microstructure have resulted in devices that cannot compete with the power conversion efficiencies of traditional silicon technologies. Conjugated block copolymers address these restrictions as we demonstrate an ability to control donor-acceptor heterojunctions through microphase-separation by utilizing these polymers in the active layer of photovoltaic cells. Block copolymer-based devices present efficient power conversion well beyond devices composed of homopolymer blends. While traditional organic solar cells rely on fullerene electron acceptors, our block copolymer device functions without the use of such compounds and can achieve efficiencies upwards of 3%, rivaling P3HT:PCBM systems. Results of X-ray scattering characterization indicates that the block copolymer solar cells can self-assemble into mesoscale lamellar morphologies primarily containing face-on P3HT crystallite orientations. Through enhancing photoconversion efficiencies by controlling the microstructure at donor-acceptor interfaces, conjugated block copolymers serve as an exciting new technology in organic photovoltaics.