Two-step brush-painted PEDOT:PSS electrodes for ITO-free organic solar cells

To demonstrate efficient and reliable indium thin oxide (ITO)-free organic solar cells (OSCs), we fabricated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrodes by two-step brush-painting of PEDOT:PSS and dimethyl sulfoxide (DMSO). While one-step brush-painted electrodes with PEDOT:PSS and DMSO mixed solution showed large deviation in morphology and efficiency, uniform and highly conductive PEDOT:PSS electrodes were obtained by successive brush-painting of PEDOT:PSS and DMSO, respectively. ITO-free OSC exhibiting power conversion efficiency (PCE) of 3.74% was successfully demonstrated by optimized successive brush-painting.