Enhancement of the power conversion efficiency by expanding the absorption spectrum with fluorescence layers

The spectral response of Poly(3-hexylthiophene) (P3HT): 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) heterojunction film is between 350 nm and 650 nm, meaning that a lot of the sunlight is lost at ultraviolet and infrared regions. We fabricated solar cells by the attachment of a fluorescence layer which absorbs UV light, and emit visible light which will be re-used by P3HT, and thus the absorption spectrum is expanded. Since N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD) has high reflectance in the visible range, the usage of UV light will not manifest; when LiF is added as an antireflection layer, PCE was enhanced from 2.50% to 2.68%.