The nanostructuring of silicon surfaces—known as black silicon—is a promising approach to eliminate front-surface reflection in photovoltaic devices without the need for a conventional antireflection coating. This might lead to both an increase in efficiency and a reduction in the manufacturing costs of solar cells. However, all previous attempts to integrate black silicon into solar cells have resulted in cell efficiencies well below 20% due to the increased charge carrier recombination at the nanostructured surface. Here, we show that a conformal alumina film can solve the issue of surface recombination in black silicon solar cells by providing excellent chemical and electrical passivation. We demonstrate that efficiencies above 22% can be reached, even in thick interdigitated back-contacted cells, where carrier transport is very\ud
sensitive to front surface passivation. This means that the surface recombination issue has truly been solved and black silicon solar cells have real potential for industrial production. Furthermore, we show that the use of black silicon can result in a 3% increase in daily energy production when compared with a reference cell with the same efficiency, due to its better angular acceptance.Peer ReviewedPostprint (author's final draft
This work demonstrates the high potential of Al 2 O 3 passivated black silicon in high-efficiency interdigitated back contacted (IBC) solar cells by reducing surface reflectance without jeopardizing surface passivation. Very low reflectance values, below 0.7% in the 300-1000 nm wavelength range, together with striking surface recombination velocities values of 17 and 5 cm/s on p-type and n-type crystalline silicon substrates, respectively, are reached. The simultaneous fulfillment of requirements, low reflectance and low surface recombination, paves the way for the fabrication of high-efficiency IBC Si solar cells using black silicon at their front surface. Outstanding photovoltaic efficiencies over 22% have been achieved both in p-type and n-type 9-cm 2 cells. 3D simulations suggest that efficiencies of up to 24% can be obtained in the future with minor modifications in the baseline fabrication process.
A. Alcañiz (a) , G. López (a) , I. Martín (a) , A. Jiménez (b) , A. Datas (a,b) , E. Calle (a) , E. Ros (a) , L.G. Gerling (a) , C. Voz (a) , C. del Cañizo (b) , R. Alcubilla (a)
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