Precise Optical Modulation of Charge Transport in 2D Organic Molecular Crystals through Tailor-Designed Photoswitchable Guest–Host Architectures

Two-dimensional organic molecular crystals (2DOMCs) have emerged as promising candidates for next-generation ultrathin electronics. However, precisely and reversibly modulating their charge-transport characteristics remains a significant challenge. Herein, we report a molecular engineering strategy to create light-programmable field-effect transistors (FETs) based on a monolayer thick 2DOMCs, which is achieved by dispersing photochromic diarylethene (DAE) guests into a crystal host matrix of 2,6-bis(4-hexylphenyl) anthracene (C6-DPA). By systematically functionalizing the DAE periphery with substituents of varying electron-donating and -withdrawing strengths, we precisely tune the HOMO energy levels of the guest molecules. We identify DAE-OCH3 as the optimal dopant, which enables a 54% modulation of the FET current within just 5 s of UV light "writing" process. Notably, the optimized C6-DPA/DAE-OCH3 (15%) guest-host system exhibits approximately 85 distinct and stable current levels, corresponding to a storage capacity exceeding 6 bits, with excellent retention over 16 days. This performance represents a significant advancement in ultrathin multilevel memories based on high-mobility organic semiconductors. Our approach establishes a general platform for developing stimuli-responsive 2D organic materials with programmable (opto)electronic properties, opening new avenues for high-density data storage and future generation intelligent (opto)electronics.