Axially Chiral Semiconducting Polymers Enabling NIR Circularly Polarized Light-Sensing Phototransistors and Neuromorphic Synapses.

Abstract

Waveplate-free detection of near-infrared (NIR) circularly polarized light (CPL) has been limited by the absence of materials that simultaneously exhibit strong NIR circular dichroism and efficient charge transport. Here, we present a family of axially chiral conjugated polymers, S- and R-pDPP4TBN-X, designed by grafting S/R-6,6'-dimethoxy-1,1'-binaphthyl (S/R-MeBN) onto a diketopyrrolopyrrole (DPP)-bithiophene backbone. By tuning the MeBN: DPP ratio, the polymers exhibit extended absorption up to ∼1000 nm, enhanced circular dichroism in the 500-870 nm region, and optimized thin-film morphology for charge mobility. Organic phototransistors based on S/R-pDPP4TBN-10 achieve hole mobilities up to 0.13 cm² V^-1 s^-1, responsivities as high as 12.52 A W^-1, detectivities on the order of 10¹¹ Jones, and dissymmetry factors (g_Iph) of 0.30 and -0.34 under 808 nm CPL, enabling unambiguous discrimination of left- and right-handed light. Beyond static sensing, these devices emulate synaptic plasticity under CPL stimulation and, when coupled with an artificial neural network, deliver classification accuracies exceeding 95%. This work establishes a modular design paradigm for compact, NIR-active CPL sensors that integrate high charge transport, pronounced chiroptical response, and neuromorphic function, paving the way for photonic encryption, wearable optoelectronics, and bioinspired computing platforms.