Ultraviolet Anti-Reflective Films

Ultraviolet (UV) anti-reflective films can improve the performance of many devices such as photoelectric detector, laser and solar cells, etc. For Si solar cells, due to the refractive index which is much higher than air, most of ultraviolet light is reflected at the surface. Reducing the reflection will improve the conversion efficiency of the solar cells. This thesis is mainly focused on the reduction of ultraviolet reflection at the silicon surface. The followings are the main points of the thesis:1. Starting from the principle of traditional anti-reflective films, we have derived the method to design the antireflective films for short wavelength light which can be absorbed by silicon.2. A kind of two-layer structure of ultraviolet antireflective films is designed. We use nano-pillar array as the upper layer and the mixture of two kinds of different materials as the bottom layer. The ultraviolet antireflective films are optimized by the TFCalc software, and the simulation results show that the films can significantly reduce the ultraviolet reflection.3. We design a kind of four-layer structure of ultraviolet antireflective films with YAG:Ce which has the down-shifting characteristic which can convert short-wavelength light to long-wavelength light. The nano-pillar arrays are used as two upper layers, so the equivalent refractive index can be adjusted. The TFCalc simulation results show that the reflection of ultraviolet incident light can be reduced to below 18%, and the reflections of the visible and infrared light are also lowered to 4%.4. The four-layer ultraviolet antireflective films with YAG:Ce are prepared. The reflection of short-wavelength light (350nm?500nm) is reduced to 16.6%, and the average reflection (350nm?1100nm) reaches to 13%. The result shows that the four-layer anti-reflective films are effetive not only to the ultraviolet, but also to the visible and infrared.