A highly self-healable polymeric system with enhanced mechanical properties is prepared by blending conventional polyurethane (PU) with functional polyimide (PI). PU and PI synthesized in this study are miscible with each other and the thermal stability of the self-healable blend (PUPI) is improved by incorporation of PI into PU. Interestingly, on adding only a small amount of PI to PU, PUPI exhibits higher self-healing efficiency and faster self-healing kinetics. Furthermore, unlike conventional self-healing materials, PUPI also has superior surface and bulk mechanical properties. A model for the mechanism for the improvement of self-healing and mechanical properties is derived by analyzing FT-IR spectra. The outstanding self-healing and mechanical properties are attributed to the unique intermolecular networks resulting from the strong supramolecular interactions between urethane groups in PU and imide groups in PI. As a result, the PI chain acts as a polymeric glue inside the PU matrix of PUPI, which results in significant enhancements in both properties mentioned previously.

The introduction of a low band-gap oligomer, oligo(benzo[1,2,5]thiadiazole-alt-3,3'''-dihexylquaterthiophene) (BT4T) improved the performance of P3HT:PCBM bulk heterojunction organic photovoltaic cells due to improved UV-vis absorption and increased P3HT crystallinity.

We report on the photovoltaic characteristics of organic/inorganic hybrid solar cells fabricated on 'flexible' transparent substrates. The solar cell device is composed of ZnO nanorod array and the bulk heterojunction structured organic layer which is the blend of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM). The ZnO nanorod array was grown on indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates via a low-temperature (85 • C) aqueous solution process. The blend solution consisting of conjugated polymer P3HT and fullerene PCBM was spin coated at a low spinning rate of 400 rpm on top of the ZnO nanorod array structure and then the photoactive layer was slow dried at room temperature in air to promote its infiltration into the nanorod network. As a top electrode, silver was sputtered on top of the photoactive layer. The flexible solar cell with the structure of PET/ITO/ZnO thin film/ZnO nanorods/P3HT:PCBM/Ag exhibited a photovoltaic performance with an open circuit voltage (V OC ) of 0.52 V, a short circuit current density (J SC ) of 9.82 mA cm −2 , a fill factor (FF) of 35% and a power conversion efficiency (η) of 1.78%. All the measurements were performed under 100 mW cm −2 of illumination with an air mass 1.5 G filter. To the best of our knowledge, this is the first presentation of investigation into the fabrication and characterization of organic/inorganic hybrid solar cells based on bulk heterojunction structured conjugated polymer/fullerene photoactive layer and ZnO nanorod array constructed on flexible transparent substrates.

We report a low-temperature aqueous solution growth of uniformly aligned ZnO nanorod arrays on flexible substrates. The substrate is Indium Tin Oxide (ITO) film coated on polyethylene terephthalate (PET). Solutions with five different concentrations of the precursors with equimolar Zinc Nitrate and Hexamethylenetetramine (HMT) in distilled water were prepared to systematically study the effect of precursor solution concentration on the structural and optical properties of ZnO nanorods. It was concluded that the precursor concentration have great influence on the morphology, crystal quality, and optical property of ZnO nanorods. The diameter, density, and orientation of the nanorods are dependent on the precursor solution concentration. X-ray diffraction and micro-Raman spectroscopy showed that the ZnO nanorods with the highest concentration of 50 mM were highly aligned and have the highest level of surface coverage. It was also found that the diameter and length of the nanorods increases upon increasing precursor solution concentration. This is the first systematic investigation of studying the effect of precursor solution concentration on the quality of ZnO nanorods grown on ITO/PET substrates by low-temperature solution method. We believe that our work will contribute to the realization of flexible organic-inorganic hybrid solar cell based on ZnO nanorods and conjugated polymer.

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