Surface passivation of n-type doped black silicon by atomic-layer-deposited SiO_2/AI_2O_3 stacks

摘要

Black silicon (b-Si) nanotextures can significantly enhance the light absorption of crystalline silicon solar cells. Nevertheless, for a successful application of b-Si textures in industrially relevant solar cell architectures, it is imperative that charge-carrier recombination at particularly highly n-type doped black Si surfaces is further suppressed. In this work, this issue is addressed through systematically studying lowly and highly doped b-Si surfaces, which are passivated by atomic-layer-deposited AI_2O_3 films or SiO_2/Al_2O_3 stacks. In lowly doped b-Si textures, a very low surface recombination prefactor of 16 fA/cm~2 was found after surface passivation by AI_2O_3. The excellent passivation was achieved after a dedicated wet-chemical treatment prior to surface passivation, which removed structural defects which resided below the b-Si surface. On highly n-type doped b-Si, the SiO_2/Al_2O_3 stacks result in a considerable improvement in surface passivation compared to the AI_2O_3 single layers. The atomic-layer-deposited SiO_2/Al_2O_3 stacks therefore provide a low-temperature, industrially viable passivation method, enabling the application of highly n- type doped b-Si nanotextures in industrial silicon solar cells.