Degradation study under air environment of inverted polymer solar cells using polyfluorene and halide salt as electron transport layers

Analysis of stability and degradation of inverted organic solar cells (iOSCs) formed by the blend PTB7Th:PC70BM, with different stacks of electron transport layers (ETLs) PFN, PFN/LiF, LiF/PFN, LiF and without one are manufactured under N-2 environment. The degradation study of the iOSCs is done following ISOS-D1 protocols under air environment, up to 7110 h. Performance parameter obtained from J-V curves such as open circuit voltage (V-oc), short circuit current density (J(sc)), fill factor (FF) and power conversion efficiency (PCE) are analyzed for each group of iOSCs with the above mentioned different stacks of ETLs and compared between of them. The cell manufactured with the stack PFN/LiF shows the highest stability over time and its T-S80 is reached to 201 h. Cells with the stack LiF/PFN and PFN show their T-S80 to 153 h and 144 h, respectively. The S-shape is presented on all J-V curves under study and are modeled using an equivalent circuit of three-diodes, in order to understand the physical mechanism related to it.