Absorption Effeciency Enhancement Of Micromorph Tandem Solar Cellwith One Dimentional Photonic Crystalas Irland Back Reflector

One of the fundamental issue underlying the design of silicon solar cells for usein realistic settings is the maximum absorption of incident sunlight over the widestpossible range of wavelengths using the thinnest possible material. MicromorphTandem Solar cell a stack of a-Si:H, top cell, and uc-Si:H, bottom cell is one of themost promising new thin-film silicon solar-cells.The challenge of Micromorph Tandem solar cell is to achieve ideal short circuitcurrent density Jsc matching between the two sub cells. Since in the tandem solarcells, the Jsc is limited by the lowest Jsc of the sub cells, because the light passesthrough the top cell only once, and the weakly absorbed light will pass into the bottomcell and is eventually absorbed there. The light-induced degradation forbids the useof thick a-Si:H solar cells. Therefore, the limitation in Jsc comes usually from the topcell which has absorption lengths that are far greater than the absorber layer thickness.And for the bottom cell, most of the light in the long wave region~>900nm isweekly absorbed by hydrogenated microcrystalline silicon.The solution alleviating this problem is to use light trapping schemes utilizingone dimensional photonic crystal based reflectors which can strongly scatter longwavelength photons and increase their optical path lengths to enhance the absorptionthrough the wide spectrum. In our work,1D Photonic crystal (1DPC) interlayerreflectors and back-reflectors are designed and integrated at the middle and back of the tandem cell to investigate optical absorption enhancement for the a-Si:H and uc-Si:H solar cells respectively.In short, this thesis is concerned with improving the Optical absorptionefficiency of Micromorph Tandem Solar Cellusing Optical Modelling and Simulation.The Software that we used is COMSOL Multiphysics version4.3b. The absorptionefficiency, reflectance and transmittance of the tandem solar cell are analyzed byvarying the thicknesses of the top a-Si:H and the bottom uc-Si:H absorber layers. Theeffect of ZnO and1DPC have been identified as an interlayer respectively,1DPC isalso investigated as back reflector. And comparing the results of the tandem with andwithout ZnO/1DPC as interlayer. Finally, we compared the absorption efficiencyenhancement by1DPC over ZnO.In our model structure SiO/TiO2/a-Si/ZnO/uc-Si/1DPC, we found an absorptionefficiency enhancement of26.59%for a-Si and3.89%for uc-Si compared to a-Si/uc-Si.We further recommend to use Three Dimensional Photonic Crystal (3DPC). Webelieve that by properly designing3DPC for use as a back reflector, the longerwavelength region of solar spectrum will be scattered and absorbed in bottom cell.