Click Chemistry Post-functionalization of Mesoporous Diketopyrrolopyrrole Dye-Sensitized TiO2/NiO Electrode: Toward New Hybrid Multicomponent Materials for Highly Efficient Photoelectrochemical Solar Cells

Immobilization of dyes or molecular assemblies on mesoporous metal oxide semiconductor are at the heart of dye-sensitized solar cells (DSSCs) and dye-sensitized photoelectrosynthesis cells (DSPECs). However, there are few works investigating robust and versatile strategy for assembling several molecular components on the metal oxide surface. Toward this objectives, we describe in this study a simple method for direct post-functionalization dyes on nanocrystalline TiO2 or NiO electrodes. The strategy procedure is based on a thermal induced Huisgen “cross-linking” reaction between a crosslinking agent and the anchored Diketopyrrolopyrrole (DPP) sensitizers. The crosslinked layer was completely characterized by ATR-IR and TOF–SIMS mass spectroscopy. The desorption experiments indicated that the stability of the crosslinked films was significantly enhanced. Moreover, photovoltaic and transient absorption spectroscopic measurements showed that the photoelectrochemical properties of the dyes were conserved after crosslinking. Next, we fabricated a two-component system on the surface of NiO photocathode using the same strategy, by introducing a naphthalene diimide (NDI), as electron acceptor, on Diketopyrrolopyrrole dyes layer. The characterization by ultra-fast transient absorption spectroscopy and photovoltaic studies revealed that an effective electron transfer occurs from the valence band of NiO to the NDI through the DPP dye, leading to a long-lived charge-separated state of 170 µs. This new post-functionalization method can certainly be extended with further polyalkyne-substituted compounds such as antenna and catalyst to build multi-components surface and therefore fabricates a poly-functional hybrid devices.