Photo-induced storage and mask-free arbitrary micro-patterning in solution-processable and simple-structured photochromic organic light-emitting diodes

Abstract

A photochromic diarylethene-based compound BMTA, which undergoes a reversible conversion between ring- open and closed isomers by alternating UV and visible light illumination, has been designed and synthesized. By utilizing a mask-free Digital Micro-mirror Device (DMD) micro-lithography system, arbitrary micro-photopatterning in polymer films doped with BMTA can be easily obtained with UV light writing. This recorded photo information can easily be erased by further visible light irradiation. The reversible and rewritable optical storage is based on photo-switched intermolecular energy transfer between the emissive host and the ring-closed isomer c-BMTA. Furthermore, the solution-processable organic light-emitting devices (OLEDs) with the single emitting layer doped with BMTA were fabricated, which exhibit rewritable memory behavior with light control. The luminescence and current density decrease significantly upon UV light irradiation, and recover by further visible light illumination. This is because the hole trapping is much facilitated in closed-ring isomer based devices, due to elevated HOMO level of c-BMTA. Without incorporating any cross-linking layer, the maximum luminescence and current density on/off ratios of this solution-processable and simple-structured device are 1.9×103 and 1.4×102, respectively. Arbitrary micro-photolithography of OLEDs by DMD system has also been demonstrated, which shows great prospects in large-scale production of high resolution OLED displays.