Inkjet printing of charge-transfer complexes for dynamic optical storage.

Distinct color changes arising from the formation of charge-transfer complexes (CTCs) offer new opportunities for designing functional devices with tunable optical responses. We developed a dynamic optical storage system using charge-transfer complexes formed between 7,7,8,8-tetracyanoquinodimethane (TCNQ) as an electron acceptor and either phenanthrene (Phe) or biphenyl (Bp) as electron donors. Reversible formation and dissociation of the charge-transfer complexes were achieved by regulating the sublimation behavior of the donor molecules, producing distinct and reproducible color transitions applicable to optical data recording and erasure. Inkjet printing enabled precise patterning of donor and acceptor molecules, facilitating the straightforward fabrication of diverse patterns without the need for complex processing. The TCNQ-Phe and TCNQ-Bp charge-transfer complexes displayed time-dependent color fading, with their decoloration rates tunable by temperature. These controllable optical responses enabled multiple applications, including rewritable paper, time-temperature indicators (TTIs), information encryption, and anticounterfeit printing. RGB color analysis verified quantitative control of color intensity and retention time through printing parameters. The printed patterns maintained high reproducibility and stability during repeated print-erase cycles. This work demonstrates a simple, solution-processable, and switchable optical information storage platform that integrates molecular-level tunability with practical processability, offering a promising approach for optical storage and information security technologies.