In the field of material chemistry, it is of great significance to develop abundant and sustainable materials for solar energy harvesting and management. Herein, after evaluating the energy band characteristics of 13 kinds of polyoxometalates (POMs), the trisubstituted POM compound K6H4[α-SiW9O37Co3(H2O)3]·17H2O (SiW9Co3) was first studied due to its relatively smaller band gap (2.23 eV) and higher lowest unoccupied molecular orbital (LUMO) level (-0.63 V vs NHE). Additionally, the preliminary computational modeling indicated that SiW9Co3 exhibited the donor-acceptor (D-A) structure, in which the cobalt oxygen clusters and tungsten skeletons act as the electron donor and electron acceptor, respectively. By employing SiW9Co3 to modify the TiO2 film, the visible photovoltaic and photocurrent response were both enhanced, and the light-induced photocurrent at 420 nm was improved by 7.1 times. Moreover, the highly dispersive and small sized SiW9Co3 nanoclusters loading on TiO2 were successfully achieved by fabricating the nanocomposite film of {TiO2/SiW9Co3}3 with the layer-by-layer method, which can result in the photovoltaic performance enhancement of dye-sensitized solar cells (DSSCs), of which the overall power conversion efficiency was improved by 25.6% from 6.79% to 8.53% through the synergistic effect of POMs and Ru-complex.

Polyoxometalate (POM)-based organic-inorganic hybrid systems are designed as p-type dyes containing double D-A1-π-A2 chains. The A1 spacers are thiophene, 1,2,3-triazole, 1,3,4-oxadlazole, thienothiadiazole units or their combinations and the A2 spacer is hexamolybdate. The electronic structures, absorption spectra, and electronic transition characteristics of systems were systematically studied on the basis of density functional theory (DFT) and time-dependent DFT (TDDFT). The highest occupied molecular orbital (HOMO) levels of systems were below the valence bond (VB) of NiO and the lowest unoccupied molecular orbital (LUMO) levels of studied systems were higher than the I2/I3(-) redox level, which benefit hole injection and dye regeneration. The HOMOs of systems were predominantly delocalized over the organic groups and Mo[triple bond, length as m-dash]N, which are more helpful to hole injection than systems . Introduction of thienothiadiazole units is an effective way to improve the light absorption ability of dyes, and inserting thiophene and 1,2,3-triazole as A1 spacers can increase the efficiency of dye in dye-sensitized solar cells (DSSC).

We use time-dependent density functional theory methods to discuss the absorption spectra, electronic transition properties, and photovoltaic performance of metalloporphyrin−polyoxometalates (POM) complexes for p-type dye-sensitized solar cells (DSSCs). The results show that the energy levels of the frontier molecular orbitals for dyes 2−6 match the requirements of p-type DSSCs. The absorption spectra of dyes 2−6 exhibit larger and broader absorptions compared to that of dye 1 by the introduction of POM. In addition, the photovoltaic performances of dyes 2−6 are suitable for high-efficiency DSSCs. This paper is expected to advance the design of metalloporphyrin−POM hybrid dyes with excellent performance in DSSCs.

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