Low-temperature solution-processed flexible organic solar cells with PFN/AgNWs cathode

We report on highly efficient flexible inverted organic solar cells (IOSCs) fabricated by low-temperature solution process on polyethylene terephthalate (PET) substrate. In general, IOSCs have been required to use an annealed (>200 degrees C) zinc oxide (ZnO) as an electron transport layer. However, any twisting of the flexible substrate during heat treatment leads to poor device performance. To overcome this issue, we developed a novel low temperature process for flexible IOSCs using an alcohol-/water-soluble conjugated polymer, namely poly [(9,9-bis(3'-(N, N-dimethylamino) propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) instead of the ZnO. Using this low-temperature process, we successfully demonstrate highly efficient flexible IOSCs that are proven to be capable of the power conversion efficiency (PCE) of 6.17% which retain 96% of its efficiency at a bending radius of R approximate to 5 mm or less. To the best of our knowledge, this PCE 6.17% is the best result among the reported values so far for flexible OSCs fabricated on PET substrate. (C) 2015 Elsevier Ltd. All rights reserved.