Injection kinetics at dye-sensitized semiconductor interfaces

The charge transfer kinetics at a semiconductor surface represents an important issue for the development of dye-sensitized solar cells (DSSC). It governs the performance of both the n- and p-type DSSCs, where either electron or hole is injected into the semiconductor, respectively.

Recently, we investigated the electron transfer kinetics from photoexcited Ru-based coordination complexes (N3 and N719 dyes) into the TiO2 and ZnO semiconductor substrates [1,2]. Applying the PES method, we were able to reveal the band alignment between the conduction band of the semiconductor and the transient singlet and triplet states of the dye molecule. It was shown that the dye-semiconductor electronic coupling is of primary importance rather than the band alignment. The formation of an interfacial complex was demonstrated to be responsible for the slow injection at the ZnO interface. Currently we investigate the hole injection dynamics into NiO sensitized with Zn-based porphyrins.

References

[1] M. Borgwardt, M. Wilke, T. Kampen, S. Mähl, W. Xiang, L. Spiccia, K. M. Lange, I. Yu. Kiyan, E. F. Aziz. Injection Kinetics and Electronic Structure at the N719/TiO2 Interface Studied by Means of Ultrafast XUV Photoemission Spectroscopy. J. Phys. Chem. C 119, 9099 - 9107 (2015). DOI: 10.1021/acs.jpcc.5b01216

[2] M. Borgwardt, M. Wilke, T. Kampen, S. Mähl, M. Xiao, L. Spiccia, K. M. Lange, I. Yu. Kiyan, E. F. Aziz, Charge Transfer Dynamics at Dye-Sensitized ZnO and TiO2 Interfaces Studied by Ultrafast XUV Photoelectron Spectroscopy, Scientific Reports 6, 24422 (2016). DOI: 10.1038/srep24422