An effective way to simultaneous realization of excellent optical and electrical performance in large‐scale Si nano/microstructures

Abstract

Abstract Despite the optical advantage of near‐zero reflection, the silicon nanowire arrays (SiNWs)‐based solar cells cannot yet achieve satisfactory high efficiency because of the serious surface recombination arising from the greatly enlarged surface area. The trade‐off between reflection and recombination fundamentally prevents the conventional SiNWs structure from having both minimal optical and electrical losses. Here, we report the simultaneous realization of the best optical anti‐reflection (the solar averaged reflectance of 1.38%) and electrical passivation (the surface recombination velocity of 44.72 cm/s) by effectively combining the Si nano/microstructures (N/M‐Strus) with atomic‐layer‐deposition (ALD)‐Al 2 O 3 passivation. The composite structures are prepared on the pyramid‐textured Si wafers with large‐scale 125 × 125 mm 2 by the two‐step metal‐assisted chemical etching method and the thermal ALD‐Al 2 O 3 treatment. Although the excellent optical anti‐reflection is observed because of the complementary contribution of Si N/M‐Strus at short wavelength and ALD‐Al 2 O 3 at long wavelength, the low recombination has also been realized because the field effect passivation is enhanced for the longer and thinner SiNWs through the more effective suppression of the minority carrier movement and the reduction of the pure‐pyramid‐textured surface recombination. We have further numerically modeled the Al 2 O 3 ‐passivated Si N/M‐Strus‐based solar cell and obtain the high conversion efficiency of 21.04%. The present work opens a new way to realize high‐efficiency SiNWs‐based solar cells. Copyright © 2014 John Wiley & Sons, Ltd.