TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Solar Cell: A difference between the refraction index of the layer of low refraction index and that of the I layer in contact with the layer of low refraction index is greater than or equal to 1.5. A thickness of the layer of low refraction index is less than 150 nm. The layer of low refraction index is made of N type silicon oxide (N-SiOx), N type silicon carbide (N-SiCx), N type silicon nitride (N-SiNx), N type amorphous silicon (N-a-Si), or N type micro-crystalline silicon (N- mu c-Si). When the layer of low refraction index is an N type silicon oxide (N-SiOx) layer, an electrical conductivity of the N-SiOx layer is greater than 10-7 S/cm. The solar cell having a reflective structure further comprises a set of bottom cells located between the N layer and the back contact, where each of the bottom cells comprises a bottom cell P layer, a bottom cell I layer, and a bottom cell N layer that are stacked together, and the layer of low refraction index comprises microcrystalline structure. The refraction index of the layer of low refraction index is lower than that of the bottom cell P layer. A solar cell having a reflective structure comprises a front contact, a P layer, an I (intrinsic) layer, an N layer, and a back contact that are stacked together, where the N layer is a multi-layer structure formed by films in such a manner that films with low refraction indexes and films with high refraction indexes are stacked alternately, and a film in contact with the I layer in the multi-layer structure is a film of low refraction index, and a refraction index of the film of low refraction index is lower than that of the I layer. A film in contact with the back contact in the multi-layer structure is a film of high refraction index, and a refraction index of the film of high refraction index is greater than that of the back contact. A difference between the refraction index of the film of low refraction index and that of the film of high refraction index is greater than or equal to 1.5. The solar cell having a reflective structure further comprises a bottom cell located between the N layer and the back contact, where the bottom cell comprises a bottom cell P layer, a bottom cell I layer, and a bottom cell N layer, and the film of low refraction index comprises microcrystalline structure. The multi-layer structure comprises the film of low refraction index, the film of high refraction index, and another film of low refraction index that are stacked together. A refraction index of the another film of low refraction index is lower than that of the bottom cell P layer.