Interface engineering and electrode engineering play important roles in the performance improvement for organic solar cells (OSCs). We here would investigate the effect of various cathode modifying layers and ITO-free electrodes on the device performance. First, for inverted organic solar cells (IOSCs) with a poly (3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61 butyric acid methyl ester blend, an aqueous solution method using low temperatures is adopted to deposit a ZnO interlayer in IOSCs. When the ZnO annealing temperature is above 80°C, the corresponding IOSCs show senior PCEs over 3.5%. Meanwhile the flexible devices based on poly(ethylene terephthalate) substrate display a PCE of 3.26% and good flexibility. Second, the performance of IOSCs based on AZO cathode and Ca modifier are studied. The resulted IOSCs with an ultrathin Ca modifier (~1 nm) could achieve a senior PCE above 3%, and highly efficient electron transport at AZO/Ca/organic interface, which obviously weakens the light soaking issue. Third, by introducing a 2 nm MoO3 interlayer for Ag anode deposition, the obtained OSCs show an improved PCE of 2.71%, and the flexible device also achieves a comparable PCE of 2.50%. All these investigations may be instructive for further improvement of device performance and the possible commercialization in the future.
Part of the book: Nanostructured Solar Cells