Controlling Polymer Morphology in Blade-Coated All-Polymer Solar Cells

eScholarship, University of California 2021-08-10

Translating all-polymer solar cells from spin-coating to scalable roll-to-roll-compatible fabrication techniques is a critical step toward the application of organic photovoltaics at a scale. Techniques to control polymer crystallization and phase separation during solution printing are essential to obtain high-performance printed organic solar cells. Here, we demonstrate a novel solvent additive approach employing trace amounts of phthalates as additives to control polymer crystallinity and suppress unfavorable phase separation in a representative PTB7-Th/P(NDI2OD-2T) all-polymer solar cell. The best-performing additive increased the blade-coated device performance from 2.09 to 4.50% power conversion efficiency, an over twofold improvement, mitigating the loss in performance that is typically observed during process transfer from spin-coating to blade-coating. It is suggested that the improved device performance stems from a finer polymer phase-separation size and overall improved active layer morphology, evidenced by device characterization data and indirectly supported by grazing incidence wide-angle X-ray scattering analyses. Real-time X-ray diffraction measurements during blade-coating provide mechanistic insights and suggest that the dioctyl phthalate additive may act as a compatibilizer, reducing the demixing of the donor and acceptor polymer during film formation, enabling a smaller phase separation and improved performance. The structural diversity of the class of phthalate additives makes this simple yet effective concept promising for translating other all-polymer material systems to blade-coating and other scalable printing techniques.

Materials; Chemical Sciences; Engineering; article

Open access content. Open access content
public

application/pdf
Chemistry of Materials vol 33, iss 15, 5951-5961 0897-4756

CDLER oai:escholarship.org:ark:/13030/qt80x7s0wq
qt80x7s0wq
https://escholarship.org/uc/item/80x7s0wq
https://escholarship.org/
1298733224

UC MASS DIGITIZATION
From OAIster®, provided by the OCLC Cooperative.

edsoai.on1298733224