Silicon-core glass fibres as microwire radial-junction solar cells

Abstract

Vertically aligned radial-junction solar cell designs offer potential improvements over planar geometries, as carrier generation occurs close to the junction for all absorption depths, but most production methods still require a single crystal substrate. Here, we report on the fabrication of such solar cells from polycrystalline, low purity (99.98%) p-type silicon starting material, formed into silicon core, silica sheath fibres using bulk glass draw techniques. Short segments were cut from the fibres, and the silica was etched from one side, which exposed the core and formed a conical cavity around it. We then used vapour deposition techniques to create p-i-n junction solar cells. Prototype cells formed from single fibres have shown conversion efficiencies up to 3.6%, despite the low purity of the starting material. This fabrication method has the potential to reduce the energy cost and the silicon volume required for solar cell production. Simulations were performed to investigate the potential of the conical cavity around the silicon core for light collection. Absorption of over 90% of the incident light was predicted, over a wide range of wavelengths, using these structures in combination with a 10% volume fraction of silicon.

Crystalline silicon core fibres from aluminium core preforms

“…3, Supplementary Note 2). Furthermore, X-ray diffraction (XRD) and Raman spectrum 30,31 help identify that the Si core wire is polycrystalline, which is similar to that of the core drawn from molten-core method 18,24 (Supplementary Figs 4 and 5). The EDX mappings shown in Fig.…”

“…The redraw technique could also be applied to achieve nanometer-scale Si wires 23 . Also the thin interface layer that lies between the core and the cladding as seen in Figs 2i and 3j could be of interest for the potential advantage on oxygen gettering and surface modification for the post-drawing process 18,39 . The smoothness of the Si is verified in the atomic force scan (AFM) image ( Supplementary Fig.…”

“…In recent years the opportunities for tighter integration between electronics and photonics have led to the emergence of the field of Si photonics where wafer processes are used to combine the best features of both materials [11][12][13][14] . In a mirror effort the advanced demonstrations of incorporating Si into fibres have been explored in electronics and photonics, such as photodetection 15 , fibre battery 16 , fibre solar cell 17,18 , electro-optical modulation 19 , material engineering 20 , non-linear optics 21,22 , pressurized Si sphere fabrication 23 and so on. Two disparate methods of producing Si-core silica-cladded fibres have been reported, the first relies on the physical flow process and the second on a chemical reaction internal to a pre-fabricated fibre.…”

Crystalline GaSb-core optical fibers with room-temperature photoluminescence

“…The literature on Group IV semiconductor-core glass fibers is now significant [1][2][3][4][5], including processing improvements [6][7][8] and device demonstrations [9][10][11][12][13][14][15][16][17]. There are also reports on both SiGe alloy and II-VI core fibers [18][19][20][21][22][23], one including low temperature photoluminescence [21].…”

Light trapping in horizontally aligned silicon microwire solar cells

“…One such design is the vertically aligned nanowire/microwire cell which has emerged as a promising candidate for achieving high conversion efficiencies at a low cost [1][2][3][4][5][6][7][8]. The majority of these solar cells consist of vertically aligned microwires with diameters D from ∼ 1 µm up to ∼ 30 µm.…”