Coatings of fluorescent coloring agent (FCA) on the solar cells are proposed to increase the energy conversion efficiency of the cells by reducing the reflection of incident light. Some optical characteristics and quantum efficiency of the FCA are clarified. The reflectance shows lower values at the excitation wavelengths, where the incident light is absorbed to excite the FCA. The red FCA coatings provide about a 30% increase in the energy conversion efficiency of the solar cell. It is also effective to coat the FCA on the solar cell with an antireflection film. The energy conversion efficiency increases by about 5%.