Bismuth-Catalyzed and Doped Silicon Nanowires for One-Pump-Down Fabrication of Radial Junction Solar Cells

Abstract

Silicon nanowires (SiNWs) are becoming a popular choice to develop a new generation of radial junction solar cells. We here explore a bismuth- (Bi-) catalyzed growth and doping of SiNWs, via vapor-liquid-solid (VLS) mode, to fabricate amorphous Si radial n-i-p junction solar cells in a one-pump-down and low-temperature process in a single chamber plasma deposition system. We provide the first evidence that catalyst doping in the SiNW cores, caused by incorporating Bi catalyst atoms as n-type dopant, can be utilized to fabricate radial junction solar cells, with a record open circuit voltage of V(oc) = 0.76 V and an enhanced light trapping effect that boosts the short circuit current to J(sc) = 11.23 mA/cm(2). More importantly, this bi-catalyzed SiNW growth and doping strategy exempts the use of extremely toxic phosphine gas, leading to significant procedure simplification and cost reduction for building radial junction thin film solar cells.

High efficiency and stable hydrogenated amorphous silicon radial junction solar cells built on VLS-grown silicon nanowires

“…A group of low melting point metals, including tin (Sn) [22][23][24][25], indium (In) [23,26,27], gallium (Ga) [28] and bismuth (Bi) [29], have been adopted to mediate the VLS growth of SiNWs in a Plasma Enhanced Chemical Vapor Deposition (PECVD) system. In this way, we have demonstrated Sn assisted SiNW growth at a substrate temperature as low as 240 1C [23], with yet a very important bonus that after growing the SiNWs into a desired length, the remnant Sn can be removed by a simple hydrogen (H 2 ) plasma etching without the need of any ex situ cleaning [30].…”

All-silicon spherical-Mie-resonator photodiode with spectral response in the infrared region

“…First, the spherical topology would allow an omnidirectional light harvesting 15 . Second, in addition to an enhanced photocurrent response above and near the band gap edge, as reported for nanowire devices [7][8][9][10][11] , the strong confinement effect appearing in high-Q optical resonances would allow IR light dwelling for a time long enough to be absorbed even beyond the absorption edge of silicon. For instance, the light trapped in a Mie mode with QB6 Â 10 3 , for a typical wavelength of 1,100 nm, would stay in the microcavity for 3,5 Â 10 À 12 s, the time needed to travel a distance of 300 mm in bulk silicon (equivalent to the thickness of a standard silicon solar cell).…”

“…The impinging light is strongly confined inside those photonic structures enhancing the photocarrier generation, as it has been observed in nanowire resonators 2,3 and in the electrooptical response of the optical cavities [4][5][6] . Simultaneously, photoexcited carriers are generated close to the collecting electrodes, boosting the power generation in photovoltaic cells [7][8][9][10][11] . Furthermore, thanks to an increased absorption near the band gap edge, some recent works report on efficiency values beyond the SQ limit 10,11 .…”

Incorporation and redistribution of impurities into silicon nanowires during metal-particle-assisted growth

“…S ilicon nanowires (SiNWs) are popular building blocks for developing a new generation of high-performance transistors 1,2 , sensors 3 and solar cells [4][5][6] . The use of nanoscale metal particles as a molten soft agent to absorb precursors and precipitate crystalline SiNWs (c-SiNWs) has enabled the fabrication of SiNWs at relatively low temperatures.…”

“…However, an immediate consequence of the metal-particle-assisted SiNW synthesis is that the catalyst metals are also constantly dissolved into the as-grown c-NWs. This could be an advantage if the incorporated elements can render desirable chemistry modification in the SiNWs, for instance, causing a suitable doping effect 4 . On the contrary, it could pose a serious threat to electronic and optoelectronic applications if the dissolved metals introduce fast recombination centres in the SiNWs, as is the case for the well-known deep-level traps caused by Au atoms in c-Si 11,12 .…”