Thiophene-rich fused-aromatic thienopyrazine acceptor for donor–acceptor low band-gap polymers for OTFT and polymer solar cell applications
作者:Rajib Mondal、Hector A. Becerril、Eric Verploegen、Dongwook Kim、Joseph E. Norton、Sangwon Ko、Nobuyuki Miyaki、Sangjun Lee、Michael F. Toney、Jean-Luc Brédas、Michael D. McGehee、Zhenan Bao
DOI:10.1039/c0jm00903b
日期:——
Thiophene enriched fused-aromatic thieno[3,4-b]pyrazine systems were designed and employed to produce low band gap polymers (Eg = 1.0â1.4 eV) when copolymerized with fluorene and cyclopentadithiophene. The copolymers are mainly investigated for organic thin film transistor and organic photovoltaic applications. Molecular packing in the thin films of these polymers was investigated using Grazing incidence X-ray Scattering. Although both fluorene and cyclopentadithiophene polymers follow similar face to face ÏâÏ stacking, the latter polymers show much smaller lamellar d-spacings due to side-chain interdigitation between the lamellae. This lead to the higher charge carrier mobilities in cyclopentadithiophene polymers (up to 0.044 cm2/V.s) compared to fluorene polymers (up to 8.1 à 10â3 cm2/V.s). Power conversion efficiency of 1.4% was achieved using fluorene copolymer in solar cells with a fullerene derivative as an acceptor. Although the cyclopentadithiophene polymers show lower band gaps with higher absorption coefficients compared to fluorene copolymers, but the power conversion efficiencies in solar cells of these polymers are low due to their low ionization potentials.