Formamidinium lead triiodide (HC(NH 2 ) 2 PbI 3 or FAPbI 3 ) is gaining increasing interest in the field of mesoscopic perovskite solar cells (PSCs) for its broader light absorption compared with the more widely studied CH 3 NH 3 PbI 3 (MAPbI 3 ). Since FAPbI 3 has two polymorphs ('black' α-FAPbI 3 and 'yellow' δ-FAPbI 3 ) at ambient temperature, where α-FAPbI 3 is the desirable photoactive perovskite phase, it becomes particularly important to suppress the formation of the non-perovskite δ-FAPbI 3 for achieving high efficiency in FAPbI 3 -based mesoscopic PSCs. In this study, we demonstrate that the judicious use of low-volatility additives in the precursor solution assists in the evolution of α-FAPbI 3 through the formation of non-δ-intermediate phases, which then convert to α-FAPbI 3 during thermal annealing. The underlying mechanism involved in the additive-modulated evolution of α-FAPbI 3 upon mesoporous TiO 2 substrates is elucidated, which suggests guidelines for developing protocols for the fabrication efficient FAPbI 3 -based mesoscopic PSCs.

Supramolecular assembly: Spherical and stable hybrid assemblies based on a cationic polymer with spermine side chains and an anionic Gd(3+)-containing polyoxometalate cluster (GdW) are prepared by electrostatic interaction. The T1-weighted MRI performance of GdW is enhanced about three times in the assemblies; meanwhile, the assemblies show good biocompatibility, which enables them to be promising candidates for MRI contrast agents.

We study experimentally second harmonic generation in a one-dimensional nonlinear photonic crystal with randomized inverted-domain structure. We show that the randomness enables one to realize an efficient broadband emission of high-quality second harmonic beam. V

A new amphiphilic molecule bearing poly(ethylene oxide) (PEO) and quaternary ammonium group, was designed and synthesized to encapsulate paramagnetic Gd(III)-containing polyoxometalate (Gd-POM) through electrostatic interaction for obtaining a water-soluble organic-inorganic hybrid building block based on POM. The yielding organic cation-encapsulated Gd-POM (OCEP-Gd) complex exhibited water-solubility and amphiphility, leading to the spontaneous self-assembly into a regular vesicular structure with PEO chains towards water phase and POM units locating at the middle. The vesicular aggregate which has a regular monolayer structure, was further studied by means of dynamic light scattering, transmission electron microscopy, and X-ray diffraction. Due to the synergy of different building units, the self-assembly of the complexes was demonstrated to be efficient to adjust the ability of Gd-POM to accelerate relaxation of water-proton, which results from the paramagnetic property of Gd-POM, to a large extent. The present work provides a new methodology to obtain water-soluble hybrid building blocks based on POM, which may generate more hybrid self-assembly structures in aqueous solution and further direct POM-based materials towards biomedical applications.