We have used Stille polycondensation to prepare a series of low-bandgap copolymers, P1−P4, by conjugating the electron-accepting pyrido[3,4-b]pyrazine (PP) moieties with the electron-rich benzo[1,2-b:3,4-b′]dithiophene (BDT) or cyclopentadithiophene (CPDT) units. P1 and P3 are based on PP and BDT units while P2 and P4 are based on PP and CPDT units. All of these polymers exhibited excellent thermal stability and sufficient energy offsets for efficient charge transfer and dissociation, as determined through thermogravimetric analyses and cyclic voltammetry, respectively. The bandgaps of the polymers could be tuned in the range 1.46−1.60 eV by using the two different donors, which have different electron-donating abilities. The three-component copolymers, P3 and P4, incorporating the thiophene and bithiophene segments, respectively, absorbed broadly, covering the solar spectrum from 350 to 800 nm. The morphologies of the blends of P3 and P4 with [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) were more homogeneous than those of P1 and P2; in addition, devices incorporating the P3 and P4 blends exhibited superior performance. The best device performance resulted from an active layer containing the P4:PC70BM blend; the short-circuit current was 10.85 mA cm−2 and the power conversion efficiency was 3.15%.

We have synthesized a narrow‐bandgap conjugated polymer (PCTDPP) containing alternating cyclopentadithiophene (CT) and diketo‐pyrrolo‐pyrrole (DPP) units by Suzuki coupling. This PCTDPP exhibits a low band gap of 1.31 eV and a broad absorption band from 350 to 1000 nm, which allows it to absorb more available photons from sunlight. A bulk heterojunction polymer solar cell incorporating PCTDPP and C70 at a blend ratio of 1:3 exhibited a high short‐circuit current of 10.87 mA/cm2 and a power conversion efficiency of 2.27%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1669–1675, 2010

Recently, the control of correlated color temperature (CCT) of artificial solid-state white-light sources starts to attract more attention since CTs affect human physiology and health profoundly. In this work, we proposed and demonstrated a method that can widely tune the CCTs of electroluminescence (EL) from white-light-emitting electrochemical cells (LECs) by employing plasmonic filters. These integrated on-chip plasmonic filters are composed of semicontinuous thin Ag film or Ag nanoparticles (NPs) both included in the indium tin oxide anode contact, which have different characteristics of plasmonic resonant absorptions that can tune the EL spectra of white LECs. The CCTs of EL from white LECs integrated with semicontinuous thin Ag film and randomly distributed Ag NPs are 5778 and 2350 K, respectively. A commercially available laser scanning system was used to locally thermal anneal the semicontinuous thin Ag film to form the randomly distributed Ag NPs on the scanned areas. Hence, these two kinds of filters can be integrated on the same chip of white LEC, giving more freedom to control the CCTs of white EL and more potential applications. In addition, the laser scanning system used here is quite often used in display manufactures so that our proposed method can be immediately adopted by the light-emitting diode industry.

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