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

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.

Automated summary

This study introduces a strategy using a binary solvent-chlorinated indium tin oxide (ITO) anode to enhance the performance of non-fullerene polymer solar cells (PSCs). Experimental results show that devices based on ITO-Cl-ODCB:H2O2 exhibit significantly better performance compared to those based on ITO/PEDOT:PSS, indicating its great potential for application in PEDOT:PSS-free PSCs.