The thin film organic photovoltaic cells (OPVs) using organic semiconductors are inferior to oxgen-resistance and water-resistance, and the OPVs have a drawback that the photoelectric conversion efficiency (η) is low. For high efficiency of the OPVs, control of bulk heterojunction (BHJ) structure in the active layer is demanded. Therefore, it is thought that we can control the BHJ structure easily if we can bring a change in the aggregated structure and the crystallinity of the BHJ structure by introducing the third component that is different from the organic semiconductor into the activity layer. In this study, we introduced peptide consisting of phenylalanine of 2 molecules into the active layer prepared by poor solvent addition effect for the organic thin film solar cells and intended to try high efficiency of the organic thin film solar cells and examined the electrochemistry characteristic of the cells.

An optical intensity distribution under light irradiation in the organic photovoltaic cell affects the absorbance of the active layer, which determines the photovoltaic performance. In this research, we evaluated the optimum thickness of the organic active layer with poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] and [6,6]-phenyl C71-butyric acid methyl ester. The spectral response of external quantum efficiency was good agreement with the simulated optical intensity distribution within a device stack as a function of the position and the wavelength. As a result, the highest photoconversion efficiency of 10.1% was achieved for the inverted device structure.