Ultrafast charge-generation dynamics through interfacial energetic modulation for high-performance single-component organic photovoltaics with 14.8% efficiency.

Abstract

Bulk heterojunction (BHJ) organic solar cells (OSCs) have achieved high efficiencies but suffer from poor morphological stability due to phase separation after long-term operation. Single-component OSCs (SCOSCs) based on double-cable polymers (DCP), offer improved stability through covalently linked donor and acceptor units. However, their efficiency remains limited by inefficient charge generation arising from extensive intermixed morphologies. Here, we report a fluorinated double-cable polymer, DCPY2-F, which achieves an outstanding efficiency of 14.8% with high short-circuit current density of 26.83 mA cm^-2. Ultrafast pump-probe transient absorption spectroscopy reveals that fluorination of DCPY2 into DCPY2-F accelerates interfacial charge transfer and long-range charge separation dynamics. The pump-push-probe transient absorption spectroscopy and steady-state electroluminescence show that the faster interfacial charge transfer arises from a reduced reorganization energy and a correspondingly accelerated molecular reorganization process (2.5 ps vs. 0.8 ps). Despite comparable acceptor aggregate sizes with DCPY2, DCPY2-F also shows faster long-range charge separation dynamics, which we attribute to a narrower charge transfer states (CTs) energetic distribution. Molecular dynamics simulations further reveal that fluorination strengthens non-covalent interactions, promoting well-aligned intermolecular donor-acceptor interfaces. These structurally and energetically ordered interfacial CT states enable ultrafast and efficient charge generation. In corresponding binary blends, fluorination similarly enhances charge-transfer dynamics and photocurrent. These findings establish a unified fluorination strategy for accelerating charge generation dynamics in both SCOSCs and blends, and provide a mechanistic understanding for improving charge generation for high-performance single-component systems.