In this study, four novel silafluorene (SiF) and benzotriazole (Btz) bearing conjugated polymers are synthesized. In the context of electrochemical and optical studies, these polymers are promising materials both for electrochromic device (ECD) and polymer solar cell (PSC) applications. All of the polymers are ambipolar (both p‐ and n‐dopable) and multichromic. Electrochemistry experiments indicate that incorporation of selenophene instead of thiophene unit increases the HOMO energy level of the polymers. Power conversion efficiency of the PSCs reached 1.75% for PTBTSiF, 1.55% for PSBSSiF, 2.57% for PBTBTSiF, and 1.82% for PBSBSSiF. The hole mobilities of the polymers are estimated through space charge limited current (SCLC) model. PBTBTSiF has the highest hole mobility as 2.44 × 10−3 cm2 V s−1. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1541–1547

A low band gap donor-acceptor (D-A) copolymer PTBTBDT, namely, poly(2-dodecyl-4,7-di(thiophen-2yl)-2H-benzo [d][1,2,3]triazole-alt-4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b 0 ]dithiophene), was designed and synthesized via a Pd-catalyzed Stille polycondensation reaction. The polymer was characterized using 1 H NMR spectroscopy, UV-vis absorption spectroscopy, cyclic voltammetry, and gel permeation chromatography (GPC). PTBTBDT has good solubility in common organic solvents, good thermal stability, broad absorption, low band gap and exhibits not only high hole mobility but also moderate photovoltaic properties. PTBTBDT displays broad absorption in the wavelength range from 300 nm to 630 nm, and its HOMO and LUMO energy levels were calculated to be À4.98 eV and À3.34 eV, respectively.Bulk heterojunction solar cells were fabricated using PTBTBDT as the electron donor and PC 70 BM as the acceptor. The device exhibits a power conversion efficiency of 2.12% with a current density of 5.45 mA cm À2 , an open-circuit voltage of 0.72 V, and a fill factor of 54% under the illumination of AM 1.5 G, 100 mW cm À2 .Under similar device fabrication conditions, the PTBTBDT based device showed considerably improved efficiency among its previously synthesized counterparts, i.e. PBDTDTBTz and PBDTBTz based devices, which have 1.7% and 1.4% efficiencies, respectively. The hole mobility of the PTBTBDT : PC 70 BM (1 : 2 w/w) blend reached up to 1.47 Â 10 À3 cm 2 V À1 s À1 as calculated by the space-charge-limited current (SCLC) method. By side-chain engineering, this study demonstrates a good example of tuning the absorption range, energy level, charge transport, and photovoltaic properties of polymers.

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In this study, the effect of Si 3 N 4 insulator layer on the electrical characteristics of Au/n-4H SiC diode was investigated. The current-voltage (I −V), capacitance-voltage (C−V) and conductance-voltage (G/w−V) measurements were carried out at room temperature condition. Under thermionic emission model, electrical parameters as zero-bias barrier height (Bo), ideality factor (n), interface states (D it), and series (R s) and shunt (R sh) resistances were estimated from forward bias I −V analyses. The values of n and Bo were about 1.305 and 0.796 eV for metal-semiconductor (MS) rectifying diode, and 3.142 and 0.713 eV for metal-insulator-semiconductor (MIS) diode with the insertion of Si 3 N 4 layer, respectively. Since the values of n were greater than the unity, the fabricated diodes showed non-ideal I −V behaviour. The energy distribution profile of D it of the diodes was calculated by taking into account of the bias dependence of the effective barrier height (e) and R s. The obtained D it values with R s are almost one order of magnitude lower than those without R s for two diodes. According to Cheung's model, R s were calculated and these values were found in increasing behaviour with the contribution of Si 3 N 4 insulator layer. In addition, the J R −V plot behaviours with linear dependence between ln(J R) vs. V 0.5 indicated that the dominant conduction mechanism in the reverse bias region was Schottky effect for both MS and MIS diodes. In the room temperature C−V measurements, different from the results of MIS diode, the values of C for MS diode was observed in decreasing behaviour from ideality with crossing the certain forward bias voltage point (∼2.5 V). The decrease in the negative capacitance corresponds to the increase of G/w.

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