Enhancing the conductivity of PEDOT PSS conducting polymer using green solvent for indium tin oxide free organic solar cells

The development of sustainable and high-performance transparent electrodes is critical for scalable ITO-free organic solar cells and next-generation flexible optoelectronics, yet conventional conductivity enhancement strategies for PEDOT: PSS rely heavily on toxic, corrosive acids that pose significant environmental and processing hazards. Despite extensive efforts using polar solvents and additives, achieving high electrical conductivity through environmentally benign materials and single-step methods remains a key challenge. Here, we report a simple, single-step pre-treatment of aqueous PEDOT: PSS dispersions with bio-based green solvents that dramatically boosts electrical conductivity while eliminating the need for hazardous acids. Ethanol, cyrene, and isoamyl alcohol increased the conductivity from 0.41 S/cm (pristine) to 823.5 S/cm, 602.7 S/cm, and 135.2 S/cm, respectively. The underlying mechanism involves effective diffusion of the green solvents into the PEDOT: PSS complex, enabling charge screening that weakens Coulombic interactions between conducting PEDOT and insulating PSS chains, followed by phase separation and selective removal of excess PSS from the film surface. This process promotes the formation of extended quinoid PEDOT conformations, enhanced crystallinity, and larger conductive domains, as confirmed by Raman, XPS, XRD, HRTEM, and AFM analyses. Ethanol-treated films achieved an outstanding figure of merit (σ dc /σ op ) of 36 at 550 nm, making them competitive with ITO for transparent electrode applications. When employed as an anode in organic solar cells, the green solvent-treated PEDOT: PSS delivered a power conversion efficiency of 1.86% with > 30-fold improvement over pristine PEDOT: PSS based OSC. This green solvent approach offers a sustainable, non-toxic and acid-free pathway to PEDOT: PSS based electrodes for eco-friendly ITO-free organic photovoltaics and flexible optoelectronic devices.