Insight into Interface Engineering at TiO2/Dye through Molecularly Functionalized Caf1 Biopolymer

The fast charge recombination kinetics and poor sensitizing ability in dye-sensitized solar cells (DSSCs) result in a significant electron loss and performance degradation. However, the retarding of electron recombination and/or increasing light-harvesting efficiency (LHE) via employing an appropriate interface modifier in DSSCs has rarely been investigated. Here, we first report a molecularly engineered Caf1 protein (both in monomeric and polymeric forms) to modify the surface states by effectively shielding the unfavorable reactions and improve the light absorption properties by introducing alternative anchoring facilities. Using the novel Caf1 biopolymer with high thermal stability (even at 90 degrees C), we achieved an unprecedented efficiency of 8.31% under standard illumination test conditions and maintain the output performance even under prolonged irradiation. Time-resolved fluorescence spectroscopy measurement reveals an improved electron transfer rate (k(ET) = 0.26 to 0.98 x 10(8) s(-1)), whereas the V-oc decay rate is lower (70% decay in 90 s) for Caf1-P@TiO2 based cells than that of bare ones (similar to 85% decay in <10 s). We attributed this trend to the presence of chains in the biopolymer structure and the enhanced population of binding facilities with sensitizer molecules, promoting rapid charge transfer into TiO2 and enhanced dye-loading capability. Our results shed light on the interface engineering, and this novel Caf1 biopolymer offers a meaningful transfer of energy to develop efficient electrochemical cells with attractive properties for scale up and practical applications.