One approach to improve the efficiency of electricity generation of solar cells is to use a luminescent/fluorescent dye that absorbs a part of the spectrum of incident light and then simultaneously emits clown-shifted light that matches the spectral response of the solar cells. In this study, the authors numerically simulated the escaping energy losses of isotropic diffuse clown-shifted light emitted by luminescent dyes doped in micro/nanostructured solar cell systems. The simulation was accomplished by using the two-dimensional total-field finite-difference time-domain (FDTD) method, which simulates not only reflection and refraction but also diffraction. Two simulation models-one based oil a V-grooved luminescent clown-shifting (LDS) layer and the other based on a planar luminescent solar concentrator (LSC)-were used, and the size effects of the LDS layer and LSC, effect of doping position on the escaping energy loss, and angle dependency of the escaping energy loss were clarified. For the V-grooved LDS layer, the escaping loss was found to be less than 10% in the wavelength range of 400-1170 nm when the height and width of the V-groove were 360 and 424 run, respectively. This value of the escaping loss is less than half of that Calculated from ray optics, which simulates only reflection and refraction. A planar LSC with a thickness of 300 nm and a length in the submicron range also exhibited smaller escaping loss than a conventional-sized one. Furthermore, the authors confirmed that the reflectance of the micro/nanostructured solar cell systems is lower than the theoretical ray optical reflectance of an air-PMMA-Flat Si layer. This indicates that doping luminescent dyes in Such micro/nanostructured solar cell systems potentially improves the light trapping efficiency of clown-shifted diffuse light emitted by the luminescent dyes. (C) 2009 Elsevier B.V. All rights reserved.