Chiral π-Conjugated Polymer Films via Kinetic-Controlled Dip-Coating for Circularly Polarized Light Information Encoding

Abstract

The development of chiral organic semiconductors with efficient circularly polarized light (CPL) detection capability is crucial for advanced optoelectronic applications, such as secure communication and optical information processing. However, translating their promising molecular-level chirality into solid-state devices remains a challenge. The core issue lies in the difficulty of controlling the quality of the active film during film formation, including ordered molecular packing and supressed surface defects, which governs both charge transport and chiral expression. Herein, we report high-quality thin films of a novel n-type chiral π-conjugated polymer, (S)-P(NDI2MH-T), fabricated via a kinetic-controlled dip-coating method. Systematic investigation of the dip-coating parameters, especially tailoring the surface wettability, reveals that the substrate with contact angle of ~36° and temperature of 25 °C at the polymer concentration of 5 mg mL⁻¹ yield continuous, pinhole-free films with enhanced molecular ordering. Based on these films, organic n-type phototransistors demonstrate a high electron mobility of 0.82 cm² V⁻¹ s⁻¹ and a high photoresponsivity of 38 A W⁻¹. Furthermore, the devices show a pronounced chiral selectivity towards CPL, with a photocurrent dissymmetry factor (gph) of up to 0.28. Leveraging this selectivity, we successfully demonstrate the application of the device in binary logic information encoding and decoding, mimicking Morse code communication. This work provides a viable pathway from material processing to device integration for constructing sensitive and integrable chiral optoelectronic systems.