Beyond Intrinsic Limits: Polarization-Sensitive Carrier Dynamics Amplify Subtle Intrinsic Optical Anisotropy into Giant Linear Dichroism.

Abstract

Filterless polarization-resolved photodetection is attractive for compact optoelectronic systems, but its polarization contrast is fundamentally constrained by the low intrinsic absorption anisotropy of semiconductors. Here, we introduce polarization-sensitive carrier dynamics (PSCD), a design principle that shifts polarization discrimination from static absorption anisotropy to the time evolution of photocarrier populations. We implement PSCD in a nonvolatile floating-gate phototransistor by integrating a molecularly thin p-type organic single crystal with a two-dimensional covalent organic framework floating gate. Orthogonal linearly polarized light generates different photogeneration rates in the anisotropic crystal, which induce distinct optical-erasure kinetics and temporally divergent recovery of the channel hole population. Consequently, the absorption linear dichroism ratio (LDR) of 3.4 is dynamically amplified by over four orders of magnitude, reaching a transient photocurrent LDR of 3.6 × 10⁴ under optimized bias conditions. The device further maintains strong polarization discrimination under partially polarized illumination, achieving a transient photocurrent LDR of 9.8 × 10² at a degree of linear polarization of 0.3. These results establish time-domain amplification of weak optical anisotropy through carrier-dynamic modulation as a strategy for filterless, high-contrast polarimetric sensing in compact optoelectronic platforms.