Nickel Silicide Nanowire Arrays for Anti‐Reflective Electrodes in Photovoltaics

Abstract

Conductive nanowires (NWs) provide several advantages as a template and electrode material for solar cells due to their favorable light scattering properties. While the majority of NW solar cell architectures studied are based on semiconductor materials, metallic NWs could provide equivalent anti‐reflection properties, while acting as a low‐resistance back contact for charge transport, and facilitate light scattering in thin layers of semiconductors coated on the surface. However, fabrication of single‐crystalline highly anti‐reflective NWs on low‐cost, flexible substrates remains a challenge to drive down the cost of NW solar cells. In this study, metallic NixSi NW arrays are fabricated by a simple, bottom‐up, and low‐cost method based on the thermal decomposition of silane on the surface of flexible Ni foil substrates without the need for lithography, etching or catalysts. The optical properties of these NW arrays demonstrate broadband suppression of reflection to levels below 1% from 350 nm to 1100 nm, which is among the highest values reported for NWs. A simple route to control the diameter and density of the NWs is introduced based on variations in a carrier gas flow rate. A high‐resolution TEM, XRD and TEM‐EDS study of the NWs reveals that they are single crystalline, with the phase and composition varying between Ni2Si and NiSi. The nanowire resistivity is measured to be 10−4 Ω‐cm, suggesting their use as an efficient back electrode material for nanostructured solar cells with favorable light scattering properties.

25th Anniversary Article: Semiconductor Nanowires – Synthesis, Characterization, and Applications

“…Metal silicides, titanium silicide (TiSi) in particular, have also been chosen as a highly conductive material to realize TiSi/TiO 2 , TiSi/WO 3 , and TiSi/Fe 2 O 3 photoanodes via atomic layer deposition. The optical properties of metal silicide NW arrays have been shown to exhibit highly efficient light‐trapping properties to minimize reflection and enhance absorption, providing a highly conductive template for coating with a thin absorbing material . WO 3 has also been reported as a core material in combination with BiVO 4 , not only for the good conductivity of WO 3 but also for its desirable band‐bending at the heterojunction, which enhances charge separation.…”

Solution-phase synthesis of single-crystal Cu3Si nanowire arrays on diverse substrates with dual functions as high-performance field emitters and efficient anti-reflective layers

“…Traditionally in electronic circuitry, metallic silicides have been widely used for Schottky diodes, metal gates, and local interconnections in complementary metal oxide-semiconductor (CMOS) devices. [8][9][10][11] A variety of metal silicide nanowires have been achieved by either silicidation of silicon nanowires, [12][13][14] delivery of Si ux on metal lms, 7,10,11,15 reactions of metals with silicon substrates, 16,17 or co-pyrolysis of organometallic precursors of metals and silicon via chemical vapor deposition (CVD) and chemical vapor transport (CVT). [3][4][5][6][7] The major challenging issues for the controlled growth of silicide nanomaterials are their many possible phases from metal-rich to silicon-rich silicides and complex phase behaviors within a narrow composition range.…”

Controlled assembly of graphene-capped nickel, cobalt and iron silicides

“…Ni-rich silicides, like Ni 3 Si, Ni 2 Si and Ni 31 Si 12 , can be used for p-MOS gates due to their higher work function, while NiSi, NiSi 2 and Ni 3 Si 2 are attractive for n-MOS applications27. Ni and Co silicides also exhibit intriguing electronic properties, especially in the form of nanowires or nanobelts28293031. The compound CoSi 2 , similarly to Ni silicides, is a material of choice to contact the source, drain and gate areas in complementary MOS1819.…”