Evaluation of thermal evaporation as a deposition method for vacuum-processed polymer-based organic photovoltaic devices

In this study, we aimed to evaluate the evaporating fractions of a polymeric material by thermal evaporation to scale up polymer-based organic photovoltaic (OPV) devices. Due to its high thermal stability and suitable optoelectronic properties, we used a poly(azomethine)-based material (PAZ2ThA2) as the donor layer. The control and reproducibility of our methodology were confirmed through two specific analyses: size exclusion chromatography, which allowed us to separate and measure the size of the deposited material, and UV–visible absorption spectroscopy, which provided information about the light absorption of the evaporated fractions. Our deposition rates reached a maximum of 1.4 Å·s−1. We fabricated bilayer OPV devices to evaluate the thickness dependence of the deposited fractions and achieved a maximum short-circuit current density of 1.60 mA·cm−2 at 9 nm thickness. These results confirm the feasibility of obtaining reproducible vacuum-processed polymer-based OPV devices, a significant step toward their scalability.