title: Nanostructure formation and passivation of large-area black silicon for solar cell applications.
abstract: Nanoscale textured silicon and its passivation are explored by simple low-cost metal-assisted chemical etching and thermal oxidation, and large-area black silicon was fabricated both on single-crystalline Si and multicrystalline Si for solar cell applications. When the Si surface was etched by HF/AgNO(3)  solution for 4 or 5 min, nanopores formed in the Si surface, 50-100 nm in diameter and 200-300 nm deep. The nanoscale textured silicon surface turns into an effective medium with a gradually varying refractive index, which leads to the low reflectivity and black appearance of the samples. Mean reflectance was reduced to as low as 2% for crystalline Si and 4% for multicrystalline Si from 300 to 1000 nm, with no antireflective (AR) coating. A black-etched multicrystalline-Si of 156 mm × 156 mm was used to fabricate a primary solar cell with no surface passivation or AR coating. Its conversion efficiency (η) was 11.5%. The cell conversion efficiency was increased greatly by using surface passivation process, which proved very useful in suppressing excess carrier recombination on the nanostructured surface. Finally, a black m-Si cell with efficiency of 15.8% was achieved by using SiO(2)  and SiN(X)  bilayer passivation structure, indicating that passivation plays a key role in large-scale manufacture of black silicon solar cells.
authors.affiliation: Beijing National Laboratory for Condensed, Matter Physics Institute of Physics, Chinese Academy of Sciences, Beijing 100190, PR China.
authors.forename: Yaoping
authors.initials: Y
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Lai
authors.forename: Hailing
authors.initials: H
authors.lastname: Li
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Zengxia
authors.initials: Z
authors.lastname: Mei
authors.forename: Huili
authors.initials: H
authors.lastname: Liang
authors.forename: Zhilei
authors.initials: Z
authors.lastname: Li
authors.forename: Fengming
authors.initials: F
authors.lastname: Zhang
authors.forename: Wenjing
authors.initials: W
authors.lastname: Wang
authors.forename: Andrej Yu
authors.initials: AY
authors.lastname: Kuznetsov
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Du