Vapor deposition of poly(hexafluorobutyl acrylate) nanocoating for encapsulation of organic solar cells

Abstract

The biggest problem of organic photovoltaics is their quickly deterioration in atmospheric conditions. O2 and moisture in the air affect device performance negatively. In this study, at first, it is determined which electrical parameter used in the device efficiency calculation is affected by atmospheric conditions. For this context, produced devices were kept in room conditions, desiccator, and glovebox, respectively. Stability tests were performed for 8 weeks. According to the results, predominantly, current density (Jsc) is affected by O2, open circuit voltage (Voc) is affected by moisture while fill factor (FF) is affected by both O2 and moisture. Normalized efficiency (eta) values are decreased, the devices kept in room conditions, desiccator, and glovebox, 90 %, 60 %, and 20 %, respectively. In the second part, devices were encapsulated with poly(Hexafluorobutylacrylate) (PHFBA) using batch initiated chemical vapor deposition (iCVD) technique at varying thicknesses. FTIR and XPS studies revealed successful PHFBA polymerization coatings. Efficiency losses for encapsulated devices was measured as between 30 and 35 %. When the non-encapsulated and encapsulated devices kept under room conditions were compared, the reductions in efficiency were found to be 90 % versus 30 %. According to the results, PHFBA has good barrier properties against O2 and moisture.