Synthesis and characterization of benzodithiophene-isoindigo polymers for solar cells

Zaifei Ma, Ergang Wang, Markus Jarvid, Patrik Henriksson, Olle Inganas, Fengling Zhang, Mats R. Andersson

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    143 Citations (Scopus)

    Abstract

    Three new alternating polymers with the electron-deficient isoindigo group as the acceptor unit and benzo[1,2-b:4,5-b′]dithiophene (BDT) or BDT flanked by thiophenes (or octylthiophenes) as the donor unit were designed and synthesized. All the polymers have good thermal stability, solubility and broad absorption spectra. Their photophysical, electrochemical and photovoltaic (PV) properties were investigated. To understand their different PV performance in the resulting polymer solar cells (PSCs), the morphology of their blends with fullerene derivatives was investigated by atomic force microscopy, and the molecular geometries as well as the molecular frontier orbitals were simulated by density functional theory calculations (Gaussian 09). The polymer PBDT-TIT, with BDT flanked by thiophenes as the donor unit and isoindigo as the acceptor unit, exhibits quite planar backbones and its blend with fullerene derivatives shows optimal morphology. As a result, the PSCs based on PBDT-TIT with a conventional device configuration of ITO/PEDOT:PSS/PBDT-TIT:PC 61BM/LiF/Al showed a power conversion efficiency of 4.22%, with a short-circuit current density of 7.87 mA cm -2, an open-circuit voltage of 0.79 V and a fill factor of 0.68 under the AM 1.5G illumination with an intensity of 100 mW cm -2 from a solar simulator.

    Original languageEnglish
    Pages (from-to)2306-2314
    Number of pages9
    JournalJournal of Materials Chemistry
    Volume22
    Issue number5
    DOIs
    Publication statusPublished - 7 Feb 2012

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