Enhancing Efficiency and Photo-Stability of Organic Solar Cells via Vertical Phase Separation Morphology Induced by Surface Modification of PEDOT:PSS with Star-Shaped Benzene-Based DFTAB Additive

As a hole transport layer in organic solar cells (OSCs), many efforts have focused on modifying PEDOT:PSS to augment its hole transport capability. In contrast, instances of utilizing organic molecules are relatively scarce, primarily due to the challenges associated with interface regulation compatibility. Herein, we present a novel approach involving the integration of 3,6-difluoro-octakis(4-methoxyphenyl) benzene-1,2,4,5-tetraamine (DFTAB), featuring star-shaped benzene moieties with an electron-poor core deeply enveloped within electron-rich surroundings. This distinctive molecular architecture prompts a transition from homogeneous to a face-on orientation feature, inducing a distinct vertical phase separation, and enhances crystallization within the active layer. Utilizing DFTAB modification, a remarkable power conversion efficiency (PCE) of 19.14% was yielded based on the PM6:ITOA:BTP-eC9 ternary device. Additionally, it enhanced the photostability of the device, benefiting from the UV absorption capacity of DFTAB. This synergistic enhancement in efficiency and stability underscores the potential of DFTAB-modified PEDOT:PSS as a promising avenue for advancing OSCs.