New Photodiode Composed of a Polymer-Metal Complex Film

4 New Photodiode Composed of a Polymer-metal Complex Film 

Photodiodes utilize principally the photophysical process of semiconductors. The most typical juctions to attain photoinduced charge separation are shown in Fig. 27 a c. If a photoexcited compound (P) is arranged with donor and/or acceptor on an electrode as shown in Fig. 25 (d), it must work as a kind of photodiode based on new principle of photochemical reaction. A polymer film must be most promising to construct such photoconversion element. 

The surface of a carbon electrode was at first coated with a thin film of an anionic polymer such as sodium poly(styrene-sulfonate) 95) or nafion 96) (thickness thousand A) then the cationic Ru(bpy)2+ was adsorbed in the anionic layer electrostatically. The modification was also made by coating water insoluble polymer pendant Ru(bpy)2 + ( ) from its DMF solution 97). These Ru(bpy) +/polymer modified electrode gave a photoresponse in the MV2+ solution with the Pt counter electrode 95-97) The time-current behaviours induced by irradiation and cutoff of the light under argon are shown in Fig. 28. It is interesting to see that the direction of the photocurrent reversed at the electrode potential of ca. 0.4 V (vs. Ag—AgCl) under 

An anisotropic photoinduced electron flow is important to produce an efficient photocurrent. The anisotropic arrangement of the reaction components is necessary for that purpose. Polymer materials are very useful to achieve such arrangement. The arrangement of Ru(bpy)j+ and MV2+ was attained by coating electrode at first with a polymer pendant Ru complex film and then with a polymer pendant MV2+ (28) film. The photocurrent induced by this bilayer coating system is shown in 

Polymer coating thus not only makes electrodes photoresponsive by incorporating photoreactive function in that layer, but also provides a kind of sew photodiode based on photochemical reaction by arranging the components in its multilayer str cture (for example, see Fig. 30). 

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