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The dependence of perovskite‐based photovoltaic devices on toxic solvents limits their applications. Therefore, we added polyoxometalates into ionic liquids, as the green solvent and polyoxometalates synergistically improve the performance of devices. Firstly, methylammonium formate (MAFa) as solvent delayed the crystallization process of perovskite thin films, thus obtained an extended crystal domain, and the photocurrent of the device was increased from 35.51 μA to 63.18 μA. Secondly, introducing PW12 into this green solvent system, the matched energy level and good electron transmission rate promoted the separation of photogenerated excitons and accelerated the transmission of photogenerated electrons in perovskite. After dual adjustment of MAFa and PW12, the photocurrent of the champion device reached 95.99 μA (about 2.7 times of the original device), the unpacked devices can still maintain 80 % of initial value after being placed under environmental conditions for 700 h. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POM) have already been confirmed to act as effective electron-transfer mediators for improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) based on previous studies. However, the improvement may be limited by the agglomeration of the polyoxoanions. In this paper, the previous synthesis strategy is improved upon by breaking the metal-organic frameworks (MOFs) with POMs as the secondary building units ([Ni(bpp)(H2O)2]3[P2W18O62] ⋅24 H2O ( 1) (bpp=1,3-bis(4-pyridyl)propane) and H6[Cu3(H2O)6(P2W18O62)2(3-dpye)6] ⋅28 H2O ( 2) (3-dpye=N,N′-bis(3-pyridinecarboxamide)-1,2-ethane)) to design and synthesize small sized and highly disperse POM nanoparticles by means of compositing with TiO2, through calcination to remove the organic ligand. TEM and element mapping confirm that P2W18O626− (denoted as P2W18) nanoparticles with the diameter of ≈1 nm are uniformly distributed in TiO2 composites. The loading amount (wt. %) of POM in MOFs reaches 75.67 %. The small sized and highly disperse P2W18 nanoparticles may provide more active sites and specific surface areas for improving the PCE of DSSCs. Finally, the investigations indicate that the PCE of composite P2W18⋅NiO@TiO2 photoanodes is up to 7.56 %, which was 26 % higher than the pristine TiO2 based photoanodes. [ABSTRACT FROM AUTHOR]

A huge 3D model of the metal‐organic framework, [Ni(bpp)(H2O)2]3[P2W18O62]⋅24 H2O, in which P2W18 clusters are the nodes in the MOF, appears at the top of the image. Many 3D models of P2W18 clusters fall from top to bottom of the image, which could symbolize that the POM‐based MOFs are broken to obtain nanosized POM clusters. A wide 3D model of the TiO2 photoanode appears at the bottom of picture to show nanosized POM clusters applied at the photoanode of a DSSC. More information can be found in the Full Paper by W. Chen, E. Wang et al. on page 8871. [ABSTRACT FROM AUTHOR]