Research Seminars in Physics

Tuesday, 6 February 2024, 15:15
Where: 21D302

Speaker: Leticia Christopholi, Department of Engineering and Physics, Karlstad University

Title: The role of processing solvent on electron-acceptor film morphology for organic solar cells

Abstract:

Organic solar cells (OSC) are a promising emerging renewable energy technology that provides a low-cost alternative to current well established photovoltaic technologies. Spin-coated small area OSCs have recently achieved power conversion efficiencies of over 19% to date, but they can also be made flexible and light weight through a continuous large-area coating process. The key molecular components of the photoactive layer are a conjugated polymer as electron donor and a non-fullerene electron acceptor (NFA), which both absorb light in the visible range and contribute to the charge photogeneration. This blend film is prepared in one step from a blend solution and form a distributed or bulk heterojunction (BHJ). Besides their advantages, NFAs also bring challenges for the processing of the photoactive layers, due to their limited solubility in commonly used organic solvents. In my PhD project, I study the morphology of the photoactive layers organic solar cells and how it influences the OSC performance. In this presentation I will focus on the neat films of the high-performance NFA molecules Y5 and Y6 and will present a rational processing strategy aiming to achieve well-ordered thin films of Y5 and Y6 by the choice of solvent. The films were studied by optical absorption spectroscopy, and atomic force microscopy and the molecular orientation in the films was examined by angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at the SOLARIS synchrotron in Poland. The next step in my project is to prepare and study the morphology of donor/acceptor bilayers, and compare their morphology and properties with BHJ films prepared from blend solutions.

https://www.kau.se/en/physics/research/research-seminars-physics