Evaluation of Optical Properties of Dye-sensitized Solar Cell Incorporating Mesoscopic Interfacial Roughness

染料敏化太阳能电池（DSC）通常具有层压结构。由于介质之间的本征折射率的差异，由于界面处的反射导致的光能损失是不可避免的。这些损耗的累积导致光电转换效率的显著降低。本文从光学阻抗匹配的角度研究了介观界面粗糙结构的作用，即“空气/玻璃/透明导电膜（ITO电极）/染料吸附TiO_2膜”和“Pt对电极”。采用射频溅射法制备了ITO和Pr薄膜。用紫外-可见-近红外光谱仪在0.24-2.60 μm波长范围内测量了样品的光学性质。使用原子力显微镜（AFM）观察表面形态。在此基础上，利用时域有限差分法（FDTD）在λ=0.4-1.0μm范围内进行了数值模拟。估算了空气/玻璃、玻璃/ ITO和ITO/染料吸附TiO_2粗糙化界面反射率分别降低3.6%、0.5%和0.5%。粗糙化后的铂膜显示出较大的漫反射率，本研究证实适当的粗糙度对于降低DSC中界面处的反射率是有用的。

Dye-sensitized solar cell (DSC) has usually a laminated structure. Optical energy loss due to the reflection at the interface is inevitable because of the difference in the intrinsic refractive index between mediums. The accumulation of these losses results in the considerable amount of the decrease of photo-electric conversion efficiency. In this study, the effect of mesoscopic interfacial rough-structure has been examined in a sense of optical impedance-matching due to the gradient-refractive index caused by the surface roughness.The structure concerned in a DSC is "air/ glass/ transparent conductive film (ITO electrode)/ dye adsorption TiO_2 film" and "Pt counter electrode". ITO and Pr films are prepared by the rf sputtering method. Optical properties of the specimens were measured using an ultraviolet-visible-near infrared spectrometer in the wavelength (λ) range of 0.24-2.60 μm. Surface morphology was observed using an atomic force microscope (AFM). Based on these observed data, the simulation of finite-difference time-domain (FDTD) method has been performed in a range of λ=0.4-1.0μm. The reductions of 3.6%, 0.5% and 0.5% in reflectance of respective roughened interfaces of air/ glass, glass/ ITO and ITO/ dye adsorption TiO_2 have been estimated. The roughened Pt film showed large diffusive reflectance.In this study, it has been confirmed that the suitable roughness is useful for the depression of reflectance at the interfaces in the DSC.