A Study on Electronic Structure of Interfaces between Substrate and Dyes for Electron Transfer Mechanism of Dye Sensitization

Dye sensitization is now understood as the electron transfer process from excited dye molecules to the conduction band of a substrate (AgX in photography and TiO2 in dye-sensitized solar cell). The electronic structure that is compatible with the electron transfer is characterized by the vacuum level shift at the interface between AgX and dyes. It was found that the alignment of permanent dipoles in organic dye molecules to the surface of AgX dominantly contributed to the vacuum level shift, while the formation of coordinate bonds between sulfur atoms with lone-paired electrons in dye molecules and silver ions on the surface of AgX gave the minor and opposite contribution to the vacuum level shift.