Dye based light sensor for tag integration

Dye based solar cells have been studied thoroughly in recent years. However, using this technology for dye based light sensors in polymer based systems offers several advantages compared to classical devices. A printable light sensor could be easily integrated into current smart label fabrication processes. Moreover, printable light sensors combined with novel conductive polymers could solve reliability issues resulting from bonding processes. In this paper we report on the fabrication of dye based light sensors using Ruthenium 535-bis-TBA as active dye and Iodide solution as charge transporting layer. A prototype has been developed and tested successfully. In order to improve the technology towards smart label integration, silica gel has been used to harden the Iodide liquid electrolyte. Depending on the silica gel concentrations, different stiffness levels can be achieved. Whereas the first light sensor prototypes have been made on glass substrates, the new ones are based on polymer substrates. The polymer foil KAPTON by Du Pont has been used as substrate. Special care has to be taken regarding the preparation of the transparent electrodes. The transparent conductive oxide (TCO) Indium Tin Oxide (ITO), which has been used as transparent electrode, has to be cured at elevated temperatures. In conclusion we have shown that dye based light sensors can be used for the integration into smart labels. Moreover modifications in the process lead to a light sensor which is compatible to future polymer based systems.