Impact of Aryl End Group Engineering of Donor Polymers on the Morphology and Efficiency of Halogen-Free Solvent-Processed Nonfullerene Organic Solar Cells

• Published in: ACS applied materials & interfaces Vol. 14; no. 8; pp. 10616 - 10626
• Main Authors: Gayathri, Rajalapati Durga, Gokulnath, Thavamani, Park, Ho-Yeol, Kim, Jeonghyeon, Kim, Hyerin, Kim, Jongyoun, Kim, BongSoo, Lee, Youngu, Yoon, Jinhwan, Jin, Sung-Ho
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.03.2022
• Subjects: Organic Electronic Devices; Flory−Huggins interaction parameter; miscibility; morphology; halogen-free solvent-processed nonfullerene organic solar cells; end group
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.1c22784

End group engineering on the side chain of π-conjugated donor polymers is explored as an effective way to develop efficient photovoltaic devices. In this work, we designed and synthesized three new π-conjugated polymers (PBDT-BZ-1, PBDT-S-BZ, and PBDT-BZ-F) with terminal aryl end groups on the side chain of chlorine-substituted benzo­[1,2-b:4,5b′]­dithiophene (BDT). End group modifications showed notable changes in energy levels, dipole moments, exciton lifetimes, energy losses, and charge transport properties. Remarkably, the three new polymers paired with IT-4F (halogen-free solvent processed/toluene:DPE) displayed high power conversion efficiencies (PCEs) compared to a polymer (PBDT-Al-5) without a terminal end group (PCE of 7.32%). Interestingly, PBDT-S-BZ:IT-4F (PCE of 13.73%) showed a higher PCE than the benchmark PM7:IT-4F. The improved performance of PBDT-S-BZ well correlates with its improved charge mobility, well-interdigitated surface morphology, and high miscibility with a low Flory–Huggins interaction parameter (1.253). Thus, we successfully established a correlation between the end group engineering and bulk properties of the new polymers for realizing the high performance of halogen-free nonfullerene organic solar cells.