Fluorine tuning of morphology, energy loss, and carrier dynamics in perylenediimide polymer solar cells

Weigang Zhu, Joaquin M. Alzola, Thomas J. Aldrich, Kevin L. Kohlstedt*, Ding Zheng, Patrick E. Hartnett, Nicholas D. Eastham, Wei Huang, Gang Wang, Ryan M. Young, George C. Schatz, Michael R. Wasielewski, Antonio Facchetti, Ferdinand S. Melkonyan, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

We investigate backbone fluorination effects in bulk-heterojunction (BHJ) polymer solar cells (PSCs) with the fluorine-poor PBDTT-FTTE and fluorine-rich PBDTTF-FTTE donor polymers, paired with the perylenediimide (PDI) 3D "propeller acceptor" Ph(PDI)3. The PBDTTF-FTTE:Ph(PDI)3 devices exhibit a >50% power conversion efficiency (PCE, up to 9.1%) increase versus PBDTT-FTTE:Ph(PDI)3. This enhancement reflects structurally optimized phase separation due to templating effects, affording reduced energy loss, higher electron mobility, greater free charge lifetimes and yields, and lower bimolecular recombination, as quantified by UPS, AFM, TEM, GIWAXS, SCLC, light intensity dependence measurements, and fs/ns transient absorption (TA) spectroscopy. In PBDTTF-FTTE, the DFT-computed dipole orientations of the ground and excitonic states are nearly antiparallel, explaining the longer free charge lifetimes, minimized recombination, and lowered exciton binding energy. The PBDTTF-FTTE:Ph(PDI)3 performance enhancement vs that of the fluorine-poor PBDTT-FTTE:Ph(PDI)3 analogue as well as the overall PSC performance exceeds that of the corresponding PC71BM- A nd ITIC-Th-based cells.

Original languageEnglish (US)
Pages (from-to)2695-2702
Number of pages8
JournalACS Energy Letters
Volume4
Issue number11
DOIs
StatePublished - Nov 8 2019

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Materials Chemistry

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