The invention discloses a broad-spectrum absorption 
black silicon solar cell structure. The structure sequentially comprises an irradiated face 
broad spectrum light 
trapping layer, a p-shaped 
silicon substrate, a n-shaped phosphorous 
diffusion layer and a backlight surface broad-spectrum absorption 
black silicon layer from top to bottom. The invention simutaneously discloses a preparation method of the broad-spectrum absorption 
black silicon solar cell structure. In the invention, the characteristics of the black 
silicon material can be fully utilized to enable sunlights entering into the 
cell to be almost absorbed; simutaneously a back 
dopant gradient can be utilized to separate eletron-hole pairs generated in the black 
silicon by a self-configuration 
field separation method, so that the eletron-hole pairs can be received and transfomred into light current by electrodes, thereby solving the problem that the traditional silicon substrate 
cell can not absorb and transform solar spectrum of which the 
wavelength is above 1.1 microns; and the PN junction of the structure is formed by diffuse junctions, the open-circuit 
voltage of the 
cell can be ensured not to be influenced by lowered black silicon lower-energy 
photon conversion, thereby effectively improving the 
photoelectric conversion efficiency of the silicon substrate sollar cell.