Porous silicon formation by HF chemical etching for antireflection of solar cells

Abstract

Macroporous and luminescent nanoporous Si are formed on Si wafers, which are modified with fine metal particles, by simply immersing the wafers in a HF solution without a bias or an oxidizing agent. The metal particles are deposited onto n-Si wafers by electroless displacement deposition from a metal salt solution including HF. The etching of Si consists of a local cathode reduction of oxygen and a local anode oxidation of Si. The porous layer is formed only on the metal-particle-deposited area of the Si wafers. The etching rate and surface morphology of Si change with the etching conditions such as dissolved oxygen concentration, kinds of metal particles, and photoillumination intensity during etching. The micrometersized macroporous Si layer is effective for the antireflection of solar cells. Efficient photoelectrochemical solar cells can be prepared by entire chemical modification of the n-Si surface.

Solar to Chemical Conversion Using Metal Nanoparticle Modified Low-Cost Silicon Photoelectrode

“…8d and e, conditions f and g, respectively). The structure change in the porous layer of multicrystalline n-Si by changing the photoillumination intensity and dissolved oxygen concentration is consistent with our previously reported results on single crystalline n-Si (Yae et al, 2005(Yae et al, , 2006b(Yae et al, , 2009). Table 1, respectively.…”

“…The metal-particle-assisted hydrofluoric acid etching can form both macroporous and microporous layers on multicrystalline Si wafers, which are modified with fine metal particles, by simply immersing the wafers in an hydrofluoric acid solution without a bias and a particular oxidizing agent (Yae et al 2006a(Yae et al , 2009. In previous papers, we reported that porous layer formation by this etching for 24 h decreased the reflectance of Si and increased the solar cell characteristics, which are not only photocurrent density but also photovoltage (Yae et al 2003(Yae et al , 2005(Yae et al , 2006a(Yae et al , 2009). …”

“…The metal-particle-assisted hydrofluoric acid etching of Si proceeds by a local galvanic cell mechanism requiring photoillumination onto Si or dissolved oxygen in the solution (Yae et al 2005(Yae et al , 2007d(Yae et al , 2009(Yae et al , 2010. Figure 5 shows a schematic diagram of n-Si and electrochemical reaction (equations (5), (6) and (7)) potential in a hydrofluoric acid solution.…”

“…0.2 mW cm -2 illumination for 6 h, dark condition for 12 h and then ca. 0.2 mW cm -2 illumination for 6 h, is suitable to produce the macro-and microporous combined structure effective for improving the solar cell characteristics (Yae et al 2005(Yae et al , 2006b(Yae et al , 2009. In this section, we applied this method to the Pt-nanoparticle-modified multicrystalline n-Si to improve the solar cell characteristics, and attempted to shorten the etching time by controlling etching conditions such as the photoillumination intensity and the dissolved oxygen concentration.…”

A Feasible Routine for Large-Scale Nanopatterning via Nanosphere Lithography

“…They have potential applications in photonic crystal devices (Yablonovitch, 1987), large-density magnetic recording devices (Chou et al, 1994), novel electronic devices (Schmidt & Eberl, 2001), synthesis of DNA electrophoresis mediate (Volkmuth & Austin, 1992)，nanocontainers , surface-plasmon resonance biosensors (Brolo et al, 2004), antireflective coatings for solar cells (Yae et al, 2005), and etc. Such broad applications of nanostructures were intimately associated with their unique properties, which are sensitively dependent on their size and/or shape.…”