A-D-A-Type Oligothiophenes Containing Benzothiadiazole Terminal Units for Small Molecule Organic Solar Cells

摘要: The electron-deficient, fused-heterocycle benzo(c)(1,2,5)thiadiazole (BTDA) is investigated as accep- tor group in A-D-A-type oligothiophenes order to corre- late their relative acceptor strength with opto-electronic and photovoltaic properties. In this respect, two novel BDTA-capped were synthesized char- acterized by optical electrochemical measurements. They showed broad absorptions the visible spectrum HOMO-LUMO energies well suited for organic solar cells. attachment of terminal BTDA units conjugated oligothiophene backbone resulted a hypsochromic shift UV-Vis absorption larger band gap comparison previously reported analogous di- cyanovinylene (DCV)-substituted indi- cating that BDTA weaker than DCV. Vacuum- processed m-i-p (metal-intrinsic-p-doped)-type bilayer so- lar cells using these co-oligomers donor C60 gave moderate power conversion efficiencies around 1.0%. Bulk-heterojunction (BHJ) pre- pared solution-processing fullerene PC61BM generated slightly lower 0.9%, which increased 1.5% higher PC71BM. It was found cell mostly limited low photocurrent densities due light devices fill factors coming from inefficient charge transport solution- BHJ devices.