Optothermal Properties of Donor–Acceptor Layers, Including PTB7, PTB7th, Y5, and Y6, for Organic Photovoltaic Cell Applications

This study addresses the development and optothermal analysis of donor-acceptor thin layers, including materials universally used in organic photovoltaic cells. This article presents the impact of temperature on the optical properties and morphology of thin films made from materials commonly used in organic solar cells. This research focused on two donor materials (PTB7 and PTB7th) and two non-fullerene acceptors (Y5 and Y6), individually and in binary combinations with PTB7 and PTB7th. This study employed various techniques, including UV-Vis spectroscopy, ellipsometry, and atomic force microscopy (AFM), to analyze changes in the absorption, refractive index, extinction coefficient, and morphology at temperatures ranging from 30 °C to 120 °C. This research shows reversible changes in thickness and absorption with temperature, but the extent of these changes differs between PTB7 and PTB7th. Y5 shows some reversible changes, while Y6 demonstrates greater instability and more permanent changes at higher temperatures. The enhanced thermal stability of binary mixtures compared to single-component materials was observed.