Fully printed organic photovoltaic employing F and N co-doped graphene oxide/polyaniline as hole extraction layer and copper nanowires as transparent conductive electrode

Organic photovoltaics (OPVs) hold great promise for flexible and lightweight solar energy applications; however, their long-term stability and efficiency remain constrained by the performance of interfacial layers. In particular, the widely used hole extraction layer (HEL) material, PEDOT:PSS, suffers from intrinsic acidity and moisture sensitivity, which adversely affect device longevity. In this study, we report a novel HEL based on fluorine and nitrogen co-doped graphene oxide-polyaniline (FNGO/PANI) synthesized via in situ oxidative polymerization of aniline in the presence of doped graphene oxide under acidic conditions. The co-doping strategy modulates the band structure of graphene oxide, enabling bandgap formation and favorable energy-level alignment while preserving carrier mobility. The FNGO/PANI composite exhibits excellent film uniformity, solution processability, and compatibility with low-temperature annealing (120 °C), making it suitable for flexible substrates and scalable fabrication. When integrated into fully printed OPVs utilizing copper nanowire (Cu NW) transparent conductive electrodes and a conventional bulk heterojunction active layer, devices incorporating FNGO/PANI as the HEL achieve a short-circuit current density (J_sc) of 16.90 mA cm⁻², open-circuit voltage (V_oc) of 0.80 V, fill factor (FF) of 69.82 %, and a power conversion efficiency (PCE) of 9.44 %. These results represent a significant improvement over devices using FNGO alone and demonstrate the synergistic benefits of co-doping and polymer integration. The findings highlight the potential of FNGO/PANI as a high-performance, solution-processable HEL for next-generation, fully printed OPV technologies.