Sequential Chiral-Layer Processing for Large Chiroptical Responses in Polymer Films and CP-LEDs
Year: 2026
Type: preprint
Abstract: Chiral small molecules can induce chiroptical responses in otherwise achiral fluorescent polymers, making these materials relevant to circularly polarized lightemitting materials and devices. Sequential deposition offers a route to chiroptical polymer films when a fluorescent polymer and a chiral small molecule cannot be readily co-processed from the same solvent. Here, poly(9,9-dioctylfluorene-altbithiophene) (F8T2) and a chiral inducer are deposited as initially separate layers from orthogonal solvents. A chiroptical response develops after thermal annealing, after which the excess inducer is reduced by selective ethanol treatment. With R-DbHP, the apparent peak absorption dissymmetry factor (|gabs|) increases from 0.09 for an optimized blend film to 0.35 for the sequentially processed film. With R-5011, the apparent film value reaches 1.06, and CP-LEDs show |gEL| up to 1.02. Across two independently fabricated devices per condition, the external quantum efficiency was 0.16–0.17% without EtOH treatment and 0.20–0.27% with treatment, and the corresponding turn-on voltages were 9V and 7V; the peak gEL remains similar, whereas the maximum luminance is lower in the treated devices. These device comparisons are exploratory and no statistical inference is made. The CD-derived values are also treated as apparent because complete polarization-artifact controls and independent validation of the largest raw ellipticities were not available. Within these limitations, the results identify sequential chiral-layer processing as a potential alternative to bulk co-doping in polymer CP-LEDs.
Source: ChemRxiv
Author: Hsin-Tso Chen
Institution: National Taiwan Normal University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204966969