Low‐Work‐Function PEDOT Formula as a Stable Interlayer and Cathode for Organic Solar Cells

Abstract Cathode with low work‐function (WF) is a vital unit in optoelectronic devices. Yet, the stable cathode is still a big challenge. Here, PEDOT:PSS‐TBA is reported among series of PEDOT:PSS‐M, where PEDOT:PSS denotes poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate), M refers to monovalent cation and TBA is tetrabutylammonium specifically, as a stable cathode. The PEDOT:PSS‐TBA is synthesized via ion exchange with WF of 4.1–4.2 eV and its conductivity can be improved to 300 S cm⁻¹ by the additive. Meanwhile, PEDOT:PSS‐TBA is stable even under plasma, heat, or isopropanol sonication. Organic solar cells (OSCs) are fabricated with indium tin oxide (ITO)/PEDOT:PSS‐TBA and highly conductive PEDOT:PSS‐TBA (with additive, hc‐PEDOT:PSS) electrodes respectively. The OSCs display superior stability than the reference with ITO/ZnO as the cathode. As a proof of concept, solution‐processed OSCs are demonstrated with a three‐layered structure (hc‐PEDOT:PSS‐TBA/active layer/PEDOT:PSS), which proves PEDOT:PSS‐TBA as a promising cathode for printable optoelectronic with a simplified structure.