Diphosphonic acid-modified PEDOT:PSS for enhanced stability and efficiency in organic solar cells: Achieving 19.5% PCE through PSS erosion mitigation and interface Optimization

Poly(3,4-ethylenedioxythiophenyl):poly(styrene sulfonic acid) (PEDOT:PSS) is valued for its electrical conductivity, transparency, and solution processability. Despite these benefits, the acidic PSS chains ionize readily in water, leading to a strongly acidic environment that affects device longevity. To address this, we introduce D3PACz, featuring bisphosphonic acid anchoring groups. The lower phosphate group anchors to ITO and modifies PEDOT:PSS to adjust its work function, while the upper group separates acidic PSS from PEDOT, mitigating PSS's corrosive effects on ITO. The D3PACz/PEDOT:PSS bilayer results in a smoother surface, facilitating active layer deposition and enhancing exciton dissociation and collection, thus improving conductivity. We then utilized this D3PACz/PEDOT:PSS as hole-transporting layer for constructing the organic solar cells devices, where a best performance of 19.5% is yielded with the enhanced photostability (PEDOT:PSS device:18.3%).