Achieving high efficiency and stability in inverted organic solar cells fabricated by laminated gold leaf as top electrodes

We investigated inverted bulk heterojunction solar cells fabricated with gold (Au) leaf as laminated top electrodes. We demonstrate that the Au leaf can be successfully transferred from a supporting polyethylene terephthalate (PET) substrate to the surface of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) due to sufficiently higher work of adhesion with PEDOT:PSS compared to PET. By optimizing the lamination conditions, the contact between the Au leaf and the PEDOT:PSS becomes homogeneous and the power conversion efficiency (PCE) improves. Using Naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole based polymer as the p-type semiconductor, the PCE reaches 5.07%. The laminated devices exhibit excellent stability comparable to that of the evaporated devices.