Macromolecules · 2005 · 189 citations · 45 references
Natural SciencesChemistryMaterials ScienceOrganic ChemistryPolymer ChemistryPolymer MaterialsOptical PolymersOrganic SemiconductorsPhotovoltaic MaterialsPolymer PhysicsSolar Cell MaterialsSolar CellsAbsorption SpectraBand GapConjugated PolymersOptical Band GapOrganic Photovoltaic CellsOrganic PhotovoltaicsOrganic Solar CellsPolythiophene
The absorption spectra of the polymers exhibit two peaks, one in the UV attributed to conjugated side chains and one in the visible due to π–π* transitions of the main chains. The study aimed to create PT4 by doubling the conjugation length of phenylene‑vinylene side chains and reducing their concentration, yielding a polymer with strong, broad visible absorption (380–650 nm) suitable for polymer solar cells. The authors synthesized six soluble polythiophene derivatives via GRIM or Stille coupling, produced PT4 with extended side‑chain conjugation, and calculated their HOMO/LUMO levels and band gaps from electrochemical measurements. The polymers’ film absorption spectra red‑shifted by 30–50 nm relative to solution, shifted further and narrowed the band gap after 130 °C annealing, XRD showed enhanced ordering and expanded interlayer spacing, and cyclic voltammetry confirmed reversible p‑ and n‑doping for all six polymers.
Six soluble polythiophene derivatives with phenylene−vinylene conjugated side chains were synthesized by GRIM or Stille methods. The absorption spectra of the polymers show two peaks located in the UV and visible region, where the visible absorption peak is attributed to the π−π* transition of the conjugated main chains and the UV absorption peak results from the conjugated side chains. By doubling the conjugation length of the phenylene−vinylene side chains and reducing the concentration of the conjugated side chains, we synthesized PT4, which possesses a strong and broad absorption in the visible region from 380 to 650 nm and is promising for the application in polymer solar cells. For the polymers of PEHPVT and PMEHPVT where every thiophene unit is attached with a conjugated side chain, the absorption spectra of their films red-shifted by 30 and 50 nm, respectively, in comparison with their solution. After thermal annealing at 130 °C for 10 min, the absorption of the films red-shifted further, and the band gap of the polymers was reduced. XRD results reveal that the ordering structure of the two polymers was enhanced and their interlayer d-spacing expanded after the annealing. Cyclic voltammograms display that the p-doping/dedoping and n-doping/dedoping processes of all the six polymers are reversible. The HOMO and LUMO energy levels and energy gap of the polymers were calculated from the electrochemical measurements.
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Hybrid Nanorod-Polymer Solar Cells
Wendy U. Huynh, Janke J. Dittmer, A. Paul Alivisatos · Science · 2002 · 5K citations
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