Solution processable planar heterojunction perovskite solar cell is a very promising new technology for low cost renewable energy. One of the most common cell structures is FTO/TiO2/CH3NH3PbI3-xClx/spiro-OMeTAD/Au. The main issues of this type of solar cell are the poor coverage and morphology control of the perovskite CH3NH3PbI3-xClx film on TiO2. For the first time, we demonstrate that the problems can be easily resolved by using a polymer additive in perovskite precursor solution during the film formation process. A 25% increase in power conversion efficiency at a value of 13.2% is achieved by adding 1 wt % of poly(ethylene glycol) in the perovskite layer using a 150 °C processed TiO2 nanoparticle layer. The morphology of this new perovskite was carefully studied by SEM, XRD, and AFM. The results reveal that the additive controls the size and aggregation of perovskite crystals and helps the formation of smooth film over TiO2 completely. Thus, the Voc and Jsc are greatly increased for a high efficiency solar cell. The amount of additive is optimized at 1 wt % due to its insulating characteristics. This research provides a facile way to fabricate a high efficiency perovskite solar cell by the low temperature solution process (<150 °C), which has the advancement of conserving energy over the traditional high temperature sintering TiO2 compact layer device.

Marine mussels anchor to a variety of surfaces in turbulent intertidal zones through the use of adhesive plaques formed from hardened mussel adhesive proteins (MAPs). It is believed that 3,4-dihydroxyphenylalanine (DOPA) imparts both water-resistant adhesive characteristics and rapid curing ability to MAPs. In this paper, DOPA-modified triblock copolymers were synthesized and used to form adhesive hydrogels. Amphiphilic block copolymers with DOPA content as high as 10 wt % were prepared, and aqueous solutions of the polymers rapidly (<1 min) formed hydrogels by photopolymerization of methacrylate end groups attached to the hydrophobic segments. Contact mechanics adhesion tests were performed on the photocured hydrogels, and it was shown that incorporating DOPA into the polymer structure significantly enhanced work of adhesion to titanium surfaces submerged in an aqueous medium. Work of adhesion values as high as 410 mJ/m 2 were recorded for polymers containing 10 wt % DOPA, although the introduction of Lys in the form of a DOPA-Lys copolypeptide reduced the work of adhesion. Oxidation of DOPA was shown to reduce work of adhesion to Ti, confirming earlier studies suggesting that the catecholic form of DOPA is largely responsible for adhesion to metal oxide surfaces. The DOPA-containing block copolymers described in this study are candidates for use as adhesive biomaterials for medical applications. Experimental SectionMaterials. 99% anhydrous HCl, 2-hydroxymethylpropane-1,3diol (HMPD), acetyl anhydride, sodium hydride (60 wt % in mineral oil, NaH), 3,6-dimethyl-1,4-dioxane-2,5-dione (LA), tert-butyldimethylsilyl chloride (TBDMS-Cl), redistilled pyridine, methacrylic anhydride, 4-(dimethylamino)pyridine (DMAP), 4 M HCl in dioxane, DOPA, di-tert-butyl dicarbonate (Boc 2 O), 2,2′-dimethoxy-2-phenylacetonephenone (DMPA), 1-vinyl-2-pyrrolidone (VP), and

We take advantage of self‐assembly in a hierarchically structured, hybrid material to develop photonic bandgaps in the visible which may be systematically tuned by application of thermal or electric fields. Hydrogen bonding between a host polymer and a guest small molecule is used to augment the molecular weight of an appropriately selected coil–coil diblock copolymer to bring the microdomain structure onto the length scale needed for significant interaction with visible light. Further, the use of liquid‐crystal‐mesophase‐forming moieties as the guest hydrogen‐bonding units adds functionality to the system as the optical properties of the liquid‐crystalline domains can be modulated by external stimuli. We use hydrogen bonding to sequester varying amounts of imidazole terminated mesogens within the acid domains of a poly[styrene‐block‐poly‐(methacrylic acid)] (PS‐b‐MAA) diblock copolymer. The resulting PS‐b‐MAA/LC side‐group liquid‐crystalline diblock copolymer possesses a photonic bandgap in the green with the exact location and structure of the gap dependent on the composition of the system. Here, we discuss the structure and optical properties of these materials as a function of their composition and the response of the optical properties to temperature. Varying the order parameter of the LC domains by heating into the isotropic state changes the peak reflectivity by 40 nm, resulting in a color change from green to orange.

In this report, we show that the microstructures of hydrogen‐bonded side‐chain liquid‐crystalline block copolymers can be rapidly aligned in an alternating current (AC) electric field at temperatures below the order–disorder transition but above the glass transition. The structures and their orientation were measured in real time with synchrotron X‐ray scattering. Incorporation of mesogenic groups with marked dipolar properties is a key element in this process. A mechanism related to the dissociation of hydrogen bonds is proposed to account for the fast orientation switching of the hydrogen‐bonded blends.

Experimental methods, characterization data and 1 H NMR and 13 C NMR spectra of monomers for all polymers are described below.Materials. Fluorene, 3-bromothiophene, 3-thiophenecarboxaldehyde and malononitrile were obtained from Aldrich Chemical Co. 9,9-Dihexylfluorene. 1 To a solution of 5.0 gm (30.1 mmol) of fluorene in THF (60 ml) at -78 o C was added dropwise, 25 ml (62.5 mmol) of n-butyllithium (2.5 M in hexane).The mixture was stirred at -78 o C for 1 h, and 11.5 gm (70 mmol) of 1-bromohexane in THF (15 ml) was added dropwise to the mixture. The solution was allowed to warm to room temperature and was stirred for overnight. The mixture was poured into water and extracted with ether (3 X 30 ml). The organic layer was washed with brine solution and dried over anhydrous MgSO 4 . The solvent was removed by reduced