The Effect of Dyes with Different π-Linkers on the Overall Performance of P-DSSCs: Lessons from Theory

A series of Keggin-type polyoxometalate (POM)-based organic-inorganic complexes (systems 2-8) were designed with different π-linkers on the basis of the molybdate-pyrene hybrid (system 1). UV-vis spectra and charge transfer (CT) parameters of designed systems were systematically analyzed by density functional theory (DFT) and time-dependent DFT (TD-DFT). The results indicate that the absorption spectra are red-shifted and the absorption intensities are enhanced with increasing number of phenylacetylene π-oligomers and introducing benzodifuranone between benzene and ethyne. However, the π-linkers near POMs are "dissolved" in the total system and the excitation occurs in a local region with increasing π-linkers. Systems 3 and 6 possess the maximum CT distance and CT charge among systems 1-5 and systems 6-8, respectively, resulting from the balance point between effectiveness of structures and delocalization. The absorption spectra of systems 6-8 obviously red-shift in comparison to systems 1-5. The present study is a further step toward the optimal absorption and CT properties.