Surface passivation of n -type doped black silicon by atomic-layer-deposited SiO2/Al2O3 stacks
B.W.H. van de Loo (Eindhoven University of Technology)
A. Ingenito (TU Delft - Photovoltaic Materials and Devices)
M. A. Verheijen (Eindhoven University of Technology)
O. Isabella (TU Delft - Photovoltaic Materials and Devices)
M. Zeman (TU Delft - Electrical Sustainable Energy)
W. M.M. Kessels (Eindhoven University of Technology)
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Abstract
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 Al2O3 films or SiO2/Al2O3 stacks. In lowly doped b-Si textures, a very low surface recombination prefactor of 16 fA/cm2 was found after surface passivation by Al2O3. 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 SiO2/Al2O3 stacks result in a considerable improvement in surface passivation compared to the Al2O3 single layers. The atomic-layer-deposited SiO2/Al2O3 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.