Influence of thiophene spacer on conjugated polymer for organic photovoltaics

A new D-A structured conjugated polymers PBDTT-TPD and PBDTT-TTPDT based on electron-rich benzo[1,2-b:4,5-b'] dithiophene (BDT) conjugated with alkylthiophene side chains with an electron-deficient 1,3-dibromo-5-(2-octyl)-4H-thieno [3,4-c]pyrrole-4,6(5H)-dione (TPD) and thiophene as a spacer were designed and synthesized via Stille coupling reaction. The polymer exhibits a broad UV-Visible absorption spectra. The HOMO and LUMO energy levels of PBDTT-TPD and PBDTT-TTPDT are -5.22 eV, -3.22 eV and - 5.72 eV, -3.55 eV respectively. The PCEs of PBDTT-TPD was found to be 1.9% efficiency.