Dynamics of biexciton polarization inversion controlled by damping and spin in conjugated polymers

The polarization inversion dynamics during biexciton decay via single-electron transition in cispolyacetylene is investigated using the extended Su-Schrieffer-Heeger model and non-adiabatic evolution method. Two key factors—damping and electron-electron interaction—are examined. Without damping, transition energy drives persistent lattice vibration, causing singlet exciton dissociation into polarons. With damping, complete polarization inversion from reverse to normal occurs. Electron-electron interaction induces dipole oscillation in singlet excitons, whereas triplet excitons relax smoothly due to Pauli-principle reduced wavefunction overlap. Results show that energy dissipation governs exciton stability, while spin configuration modulates interelectronic repulsion to determine dynamical pathways. This work reveals the microscopic mechanism of polarization inversion and offers insights for spin-controlled optoelectronic processes in organic semiconductors.