Fundamental Studies of Ternary Blends for Bulk heterojunction Solar Cells Public Deposited

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  • March 22, 2019
Creator
  • Kelly, Mary
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Organic photovoltaics have risen to prominence in the last twenty-five years, with efficiencies broaching 12 %, but the inherent limitation of a narrow absorption window has restricted the performance of these solar cells. Ternary blends offer an attractive solution to this conundrum: combining the extended complementary absorption of a tandem solar cell with the ease of single-junction fabrication. Parallel-like bulk heterojunctions (PBHJ) not only exhibit improved current, but a tunable voltage, which is a promising development. However, the development of such ternary blends is still largely an empirical process. In this dissertation, we investigate the guidelines for material selection for ternary blend solar cells. We begin by ascertaining the importance of backbone structure for compatibility in PBHJ OPVs. It immediately becomes clear that to obtain a working PBHJ, a common donor moiety is required in the polymer backbone. We build on this by comparing the performance and behavior of a physically fluorinated vs. chemically fluorinated system. In this case, the characteristics of both blends are nearly identical, indicating that compatible, miscible polymers will behave similarly to their random copolymer. Additionally, this study highlighted that the addition of a high mobility polymer into a PBHJ can improve the hole mobility and fill factor. Finally, we used these guidelines to selected high performance polymers for use in PBHJs and tested their behavior. Interestingly, with these polymers, the behavior of the physical blend differed significantly from that of the copolymer, demonstrating the complexity of ternary blends. What is true of one materials system may not hold for another.
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Rights statement
  • In Copyright
Advisor
  • Atkin, Joanna
  • Warren, Scott
  • You, Wei
  • Sheiko, Sergei
  • Cahoon, James
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill
Graduation year
  • 2017
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