Circularly Polarized Electroluminescence and Spin‐Polarized Carrier Transport in Chiral‐Doped Polymer Films

ABSTRACT

Circularly polarized electroluminescence (CPEL) based on spin‐dependent light emission is of considerable interest for functional chiral optoelectronics and spin‐photonic applications. Here we report CPEL from devices incorporating achiral poly(9,9‐dioctylfluorene) (PFO) thin films doped with enantiopure chiral perylene diimide derivative (chiral‐BPP). Thermal annealing induces supramolecular chirality in the otherwise achiral polymer matrix, leading to pronounced circular dichroism and circularly polarized luminescence. The chiral‐doped films exhibit clear electroluminescence (EL) with circular polarization, showing dissymmetry factors on the order of 10 ⁻³ . The EL spectra display voltage‐dependent evolution arising from the interplay between polymer emission and excimer emission from aggregated chiral dopants, which is attributed to a recombination mechanism involving exciton–polaron quenching. Magnetic conductive atomic force microscopy (mc‐AFM) measurements reveal spin‐selective carrier transport in the chiral‐doped films, with opposite spin polarization observed for the two enantiomers, consistent with chiral‐induced spin selectivity (CISS). These results suggest that spin‐polarized carrier recombination may contribute to the observed CPEL, in addition to the conventional chirality‐induced emission process. This work demonstrates that chiral doping provides a simple strategy for introducing spin‐selective carrier transport and CPEL into achiral polymer semiconductors.