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Abstract: Nanoparticles (NPs) having different surface capping agent, variant electrical conductivity and sunlight absorption have been studied for the ternary hybrid containing poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) in bulk heterojunction (BHJ) organic photovoltaics (OPVs). These NPs are composed of conducting gold, semiconducting CdS or PbS, or insulating cage-like molecular silica (POSS). We use a series of microscopic methods including TEM, AFM, SEM, optical, and fluorescence microscopy to estimate NP size and to probe the agglomeration and/or aggregation of NPs in P3HT/PCBM blends. Surface capping agent aromatic thiophenol (SPh) was found to be poor in the dispersion of NPs in P3HT/PCBM blends. The light harvesting of these NPs ranges from transparent (POSS NP), near transparent (CdS NP), visible light absorbing (Au NP), to near-infrared absorbing (PbS NP). Nevertheless, the absorbance of these NPs is all too small relative to that of P3HT polymer. Concerning the charge separation of P3HT exciton, the LUMO energy levels of these NPs have been determined by the combination of optical band-gap energy and HOMO energy levels. By the transient photocurrent time-of-flight method, charge carrier mobility of P3HT/PCBM/NP(CdS-SPh) ternary hybrid was found to be improved, although fluorescence quenching studies imply insufficient or ineffective contact between P3HT and all NPs in the present study. NPs hybrid P3HT/PCBM BHJ OPVs were fabricated by solution process. Regardless of conductivity or sunlight absorbance, all NPs show no improvement on power conversion efficiency of ternary hybrid OPVs, which is 3.03–3.91% less than 4.0–4.1% of P3HT/PCBM OPVs without NPs. Based on the present study, a few problems that associate with the inferior performance of NPs hybrid P3HT/PCBM BHJ OPVs are delineated. [Copyright &y& Elsevier]

Abstract: To obtain nonlinear optical (NLO) polyimides exhibiting excellent thermal stability and large electro-optical (EO) coefficients, we synthesized a series of novel hyperbranched polyimides from a tris(ether anhydride) [1,1,1-tris[4-(3,4-dicarboxyphenoxy)phenyl]ethane trianhydride (III)] and a difunctional chromophore [(2,4-diamino-4′-(4-nitrophenyldiazenyl)azobenzene) (DNDA)], through ring-opening polyaddition at room temperature to form poly(amic acid)s (PAAs), followed by poling/curing process. The presence of the imide rings in the hyperbranched NLO polymers imparted them with excellent thermal stability. Moreover, their highly hyperbranched architectures resulted in site-isolation effects, which restricted the aggregation of the chromophore units. All of these hyperbranched polymers exhibited larger EO coefficients (14.6–17.2pmV−1) and better temporal stability at 120°C than those of linear NLO polymers. In addition, we also observed waveguide properties for hyperbranched NLO polymers (3.4–4.6dBcm−1 at 1310nm). Relative to the analogous linear NLO polyimide, the hyperbranched NLO polyimides exhibited superior temporal stability, larger EO coefficients, and lower optical losses. [Copyright &y& Elsevier]

Abstract: The purpose of this study is to determine the effects of process parameters on optical quality of lenses during injection molding. The quality characteristics chosen are light transmission, surface waviness and surface finish. The Taguchi method is used to perform screening experiments to identify the important significant process parameters affecting quality of lenses. Through empirical and theoretical analysis, the most significant process parameters affecting surface waviness is the melt temperature, followed by mold temperature, injection pressure and packing pressure. On the other hand, injection molding process parameters are found to have little effect on light transmission and surface finish of lenses. Regression approach is then implemented based on surface waviness data from full factorial experiments to formulate the regression models. Three different regression methods are used, namely, linear, exponential and nonlinear regression. Verification experiments are executed to examine the accuracy of the regression model for predicting quality characteristics of lenses. The result showed the highest accuracy prediction of surface waviness was from a nonlinear regression model. An error of only 4.24% suggested the existence of a correlation among injection molding process parameters. [Copyright &y& Elsevier]