HOPV12 - Blogs

4 th Hybrid and Organic Photovoltaic Conference -Uppsala 2012 85
B39 - Synthesis and characterization of benzodithiophene–isoindigo polymers for
solar cells
Zaifei Ma a , Ergang Wang b , Markus Jarvid b , Patrik Henriksson b , Olle Inganäs a , Fengling Zhang a ,
Mats Andersson b
a, Department of Physics, Chemistry and Biology (IFM), Linköping university, Linköping university, Linköping, 58183, Sweden
b, Department of Chemical and Biological Engineering/Polymer Technology, Chalmers University of Technology, Göteborg, 41296,
Sweden
Three new alternating polymers with the electron-deficient isoindigo group as the acceptor
unit and benzo[1,2-b:4,5-b0]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:PC61BM/LiF/Al showed a power conversion efficiency of 4.22%, with
a short-circuit current density of 7.87 mA/cm2, 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/cm2 from a solar
simulator.
© SEFIN 2012