Configuration effect in polyoxometalate-based dyes on the performance of DSSCs: An insight from theoretical perspective
The electronic properties of dyes can be readily tuned by modifying the structure. Herein, the polyoxometalate (POM)-based dyes derived from dye XW11 with new patterns, donor–acceptor–π linker–acceptor (D–A–π–A) structure (dye 1), and D–π–A–π–A structure (dye 2) were designed by inserting POM moiety besides the extensively exploited D–π–A structure (dye 3). Based on density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, the configuration effect on designed dyes was investigated. The results indicate that dye 3 possesses the largest short-circuit photocurrent density JSC due to the red-shifted absorption spectra, superior intramolecular charge transfer (ICT) parameters and largest electron injection efficiency. At the same time, dye 1 with D–A–π–A structure not only benefits for the conduction band energy shift, but also retards the charge recombination and dye aggregation effect, which is beneficial for open-circuit photovoltage VOC. Moreover, the dynamics analysis of interfacial electron transfer shows that the electrons in dye 1 are almost completely injected after 14 fs, while it takes a long time for dyes 2 and 3. The present work is expected to establish the structure-property relationship for dye design.