Reducing Reflection Of Silicon Solar Cells With YAG:Ce Phosphors

Photovoltaic(PV)technologies for solar energy conversion represent promising routes to green and renewable energy generation.Despite relevant PV technologies being available for more than half a century,the production of solar energy remains costly,largely owing to low power conversion efficiencies of solar cells.The main difficulty in improving the efficiency of PV energy conversion lies in the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the band-gap of a semiconductor material.In recent years,luminescent materials,which are capable of converting a broad spectrum of light into photons of a particular wavelength,have been synthesized and used to minimize the losses in the solar-cell-based energy conversion process.Recent progress in the development of spectral converters,with a particular emphasis on lanthanide-based up-conversion,quantum-cutting and down-shifting materials,for PV applications.In addition,the technical challenges that arise in developing cost-effective high-performance solar cells based on these luminescent materials.Silicon solar cells have poor spectral response to the shorter wavelength photons.These photons are absorbed before reaching PN junction and cannot generate separate electron-holes pairs because of their high absorption coefficient.One of the potential solutions is to introduce luminescent down-shifting materials on the surface of the solar cells.These materials have ability to absorb the ultraviolet(UV)or blue light and re-emit visible or near-infrared light.YAG:Ce is one of the most preferable LDS material,which absorbs photons typically in the range of 0.2-0.5?m,and re-emits them at a longer wavelength where the solar cells shows a significantly better spectral response.However,introducing YAG:Ce phosphors into solar cells brings the increase of the surface reflection,and will negatively influence the performance of the cells.Therefore,it is important to reduce the reflection brought by the phosphors.In this work different diameters of inexpensive YAG:Ce phosphor particles with EVA have been used on the surface of crystalline silicon solar cells.The influence of different size of YAG:Ce particles with different periodicity were investigated.Ce-doped yttrium aluminum garnet(YAG:Ce)particles having diameter 10?m um and 15?m were introduced as luminescent down shifting(LDS)on the surface of mono-crystalline silicon solar cells.The particles were printed on the solar cells by using screen printing method.They convert ultraviolet and blue light into yellow light.Simulation has done by using optical ray tracing software "TracePro" and "AutoCAD." Simulation and experimental results show that the introduction of YAG:Ce particles having diameter 15?m improves the conversion efficiency from 16.64%of the cells to 17.47%of the module.The increasing efficiency is attributed to LDS effect of YAG:Ce particles and the reduced reflection of short wavelength photons.