Strain discovered in hybrid perovskite films made by existing methods affects perovskite solar cells’ intrinsic stability.

Layered perovskites have been shown to improve the stability of perovskite solar cells while its operation mechanism remains unclear. Here we investigate the process for the conversion of light to electrical current in high performance layered perovskite solar cells by examining its real morphology. The layered perovskite films in this study are found to be a mixture of layered and three dimensional (3D)-like phases with phase separations at micrometer and nanometer scale in both vertical and lateral directions. This phase separation is explained by the surface initiated crystallization process and the competition of the crystallization between 3D-like and layered perovskites. We further propose that the working mechanisms of the layered perovskite solar cells involve energy transfer from layered to 3D-like perovskite network. The impact of morphology on efficiency and stability of the hot-cast layered perovskite solar cells are also discussed to provide guidelines for the future improvement.

Here we explored the potential of using copper as the electrode material for long-term stability of perovskite solar cells.

Rapid growth in the field of supramolecular chemistry 1 has resulted in a new generation of conformationally rigid polyhedral structures of controlled shape and size which can be built from the spontaneous assembly of complementary subunits. The structural and functional features of the self-assembled product may be entirely encoded in its components without the use of templates. 2 The resulting ensemble possesses a central void that makes it potentially useful for the development of molecular sensors, new types of catalysts, and various other materials with useful properties. 3 Here we report the preparation of dodecahedra with outer dimensions of ∼5 and ∼8 Å. The actual process of self-assembly of a single dodecahedron molecule involves formation of 60 metal-ligand bonds and participation of 50 individual molecules. As the size of these self-assembled metallocyclic structures increases, the rigidity of the individual building blocks becomes essential for transmission of directing effects over larger distances. Flexible linear connectors cause the formation of oligomers instead of discrete molecules with defined shape presumably due to the formation of defects which cannot selfcorrect.The most complex of the five Platonic polyhedra, the dodecahedron, contains 12 fused five-membered rings that comprise the highest symmetry group I h . Its 12 pentagonal faces are formed from 20 vertexes and 30 edges; hence it can be prepared via edgedirected assembly from 20 tridentate angular subunits with approximately 108°directing angles combined with 30 bidentate linear subunits (Figure 1). A suitable angular subunit, tri(4′-pyridyl)methanol (1), was prepared from the known di(4-pyridyl)-ketone 4 in good yield. X-ray crystallographic analysis established the structure of compound 1 (Figure 2), 5 demonstrating that the tetrahedral directing angles in 1 are near the optimal 108°. The linear bidentate units bis[4,4′-(trans-Pt(PEt 3 ) 2 OTf)]benzene (2), bis[4,4′-(trans-Pt(PPh 3 ) 2 OTf)]biphenyl (3), and bis[4,4′-(transPt(PEt 3 ) 2 OTf)]biphenyl (4) were prepared according to procedures previously described. 6 Bis[1,4-(trans-Pt(PPh 3 ) 2 OTf)]ethynylbenzene (5) was obtained via a base-catalyzed coupling of 1,4-diethynylbenzene with trans-diiodobis(triethylphosphine)platinum(II) and subsequent treatment with AgOTf.When a solution of the angular component 1 in acetone was added to the linear unit 2 in dichloromethane, under careful monitoring of the stoichiometry by 1 H and 31 P NMR, a selfassembled dodecahedron 6 was formed in 99% isolated yield. The observed 1 H, 31 P, 13 C NMR spectra 5 are all consistent with the formation of a single, highly symmetrical molecule. This molecule has 60 positive charges and contains 60 triflate counterions. Its estimated diameter along the 3-fold axis is about 5.5 nm and it has a molecular weight of 41656.0 Da, making it comparable in size and molecular weight to small proteins. Despite the large size and molecular weight, it is remarkably soluble in polar organic solvents, presumably due to ext...