PEDOT:PSS‐Free Polymer Non‐Fullerene Polymer Solar Cells with Efficiency up to 18.60% Employing a Binary‐Solvent‐Chlorinated ITO Anode

Abstract Despite the tremendous development of different high‐performing photovoltaic systems in non‐fullerene polymer solar cells (PSCs), improving their performance is still highly demanding. Herein, an effective and compatible strategy, i.e., binary‐solvent‐chlorinated indium tin oxide (ITO) anode, is presented to improve the device performance of the state‐of‐the‐art photoactive systems. Although both ODCB (1,2‐dichlorobenzene) solvent‐ and ODCB:H₂O₂ (hydrogen peroxide) co‐solvent‐chlorinated ITO (ITO‐Cl_‐ODCB and ITO‐Cl_‐ODCB:H2O2) show similar optical transmittance, electrical conductivities, and work function values, ITO‐Cl_‐ODCB:H2O2 exhibits higher Cl surface coverage and more suitable surface free energy close to the poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐buffered ITO anode (ITO/PEDOT:PSS). As a direct consequence, the performance of ITO‐Cl_‐ODCB‐based PBDB‐T‐2F:BTP‐eC9:PC₇₁BM PSCs is comparable as the bare ITO‐based devices. In contrast, the performance of ITO‐Cl_‐ODCB:H2O2‐based devices with both small and the scaled‐up areas significantly surpass the ITO/PEDOT:PSS‐based devices. Furthermore, detailed experimental studies are conducted linking optical property, blend morphology, and physical dynamics to find the reasons for the performance difference. By applying the ITO‐Cl_‐ODCB:H2O2 anode to six other photovoltaic systems, the device efficiencies are enhanced by 3.6–6.2% relative to those of the ITO/PEDOT:PSS‐based control devices, which validates its great application potential of co‐solvent‐modified ITO anode employed into PEDOT:PSS‐free PSCs.