Bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole) (BTQBT) templating effect on structure and performance of organic solar cells

We have studied the templating effect of bis(1,2,5-thiadiazolo)-p-quinobis(1,3-dithiole) (BTQBT) on structure and performance of organic solar cells having the multilayer of ITO/BTQBT/metal-free phthalocyanine (H₂Pc)/C₆₀/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Al. Orientation of H₂Pc molecules has been studied by infrared reflection-absorption spectroscopy. The angle between the molecular plane and the substrate surface was 82° for an ITO/H₂Pc sample, whereas 32 ° for an ITO/BTQBT/H₂Pc sample. The angle depends on the materials below the H₂Pc layer. The short-circuit current was increased from 3.97 to 5.45 mA/cm² by the insertion of the BTQBT layer. This result probably originates from the change in orientation of H₂Pc molecules. The power conversion efficiency of the solar cell with the ITO/BTQBT/H₂Pc/C₆₀/BCP/Al structure was 1.4 %, whereas that of a cell without the BTQBT layer was 1.1 %. The efficiency was also enhanced by the insertion of the BTQBT layer.