A light-triggered molecular switch for an efficient OFET-based organic memory device

Abstract

Organic memory devices are currently being actively developed for use in flexible and wearable electronics, smart packaging, etc. Organic memory elements with purely electrical or electrooptical programming have become widespread, while their characteristics still need to be improved. In contrast, the inherent advantages of using molecular switches triggered by absorption of photons of different wavelengths have not been exploited yet. The application of organic photochromic compounds in optical memory devices has been restricted so far mainly due to the hindered photoisomerization of these molecules in the solid state, as the optical programming of the devices requires typically very long times (minutes or tens of minutes), whereas the switching effects are negligibly small. Herein, we present a new concept for organic optical memory design, which utilizes a redox-active photochromic molecular switch, whose photoisomerization is triggered through light-induced charge separation. In particular, ionic spiropyran/merocyanine with a chromooxalate anion [Cr(C₂O₄)₃]³⁻ was used to fabricate an OFET-based optical memory device modulated by light with wavelengths of 405 and 532 nm, which delivered an impressive switching coefficient K_SW of 65 and a memory window of 2.4 V. The use of electrooptical programming improved the device performance and enhanced K_SW up to 3.14 × 10³. Thus, the obtained results show the great potential of using light-induced charge separation as an additional driving force to facilitate photoisomerization of photochromic molecules in the solid state. Going beyond the presented OFET-based memory devices, the developed approach paves a way to the design of a new generation of light-triggered single molecule magnets and high-density molecular memory devices.