Revealing the Morphology of Non-Fullerene Based Organic Solar Cells Using Vapor Phase Infiltration

events hall

Mr. Oded Nahor - PhD candidate

27.10.2022

David Wang Auditorium, 3rd floor Dalia Meidan Bldg.

14:30

Organic solar cell (OSC) bulk heterojunctions (BHJ) typically feature a rich phase morphology with the phase composition and distribution significantly affecting processes such as charge generation, recombination and extraction, and, in turn, device performance. While fullerene-based BHJs are relatively well understood structurally, especially when blends with a flexible-chain donor are employed, donor:non-fullerene acceptor (NFA) blends are more challenging to elucidate. The reason is that NFAs often display different polymorphs; moreover, their glassy states can be complex. In this study, we developed a method that uses vapor phase infiltration (VPI) and allows direct imaging of the NFA-based blend morphology. We applied different protocols and revealed the conditions for physical affinity or chemical reaction between the gaseous precursors and the NFA. These interactions lead to a unique staining mechanism with distinct feature characteristics. We then used the VPI-imaging method together with differential scanning calorimetry (DSC) and grazing incidence wide-angle x-ray scattering (GIWAXS) to study the phase evolution of a typical NFA-based OSC blend as a function of blend composition and temperature. The combination of techniques allows us to identify the co-existence of two glassy phases: an NFA-rich one and a mixed donor-acceptor one and their distribution in the different films. Our observations help to explain earlier device results and highlight the complexity of NFA-based BHJs, emphasizing the need for a deeper understanding of the phase behavior of such systems.

BIO

  • 2006-2010 B.Sc.: Materials engineering and Chemistry, Technion
  • 2011-2013 M.Sc.: Nanoscience and Nanotechnology (RBNI), prof. Gitti Frey group.
  • 2013-2018 Rafael- advanced defense systems ltd.: Team manager, professional group leader, research leader, and composite engineer.

Advisor: Prof. Gitti Frey