Organic room temperature phosphorescence (RTP) is used to realize rewriteable (>40 cycles), transparent and flexible optical tags with high resolution (>700 dpi). The devices contain an organic biluminescent emitter doped into polymethylmethacrylate (PMMA). They show phosphorescence, which in general is quenched by molecular oxygen. However, by illuminating with ultraviolet light (365 nm), this molecular oxygen locally vanishes at the irradiated area, enabling RTP at defined spots. Further, by illuminating with infrared light, the system can be refilled with oxygen leading to quenching of the RTP again. Therefore, any luminescent pattern can be written into and erased from the tag using light only.
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