Conductive Conjugated Polyelectrolyte as Hole-Transporting Layer for Organic Bulk Heterojunction Solar Cells

Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been extensively used as the hole‐transporting layer (HTL) in bulk heterojunction (BHJ) solar cells, however, its anisotropic electrical conduction and intrinsic acidic nature generally limit the device performance. Here we demonstrate the application of a water/alcohol soluble CPE (CPE‐K) as HTLs in BHJ solar cells, achieving a PCE up to 8.2%. The more superior and uniform vertical electrical conductivity found in CPE‐K reduces the series resistance and provides efficient hole extraction.