High bandgap dielectrics for antireflective coating in silicon solar cells by reactive ion sputtering

Abstract

High bandgap materials have recently attracted a lot of interest for their potential application in photovoltaics (PV). Aluminium nitride (AlNx) is a potential candidate for the passivation and antireflective coating on silicon solar cells. AlNx thin films have been deposited by a remote plasma deposition system HiTUS (High Target Utilisation Sputtering). The AlNx thin films were grown by reactive sputtering from an aluminium target in a N2 atmosphere, negating the use of silane gas commonly used in PECVD deposition. PC1D simulations have been performed to calculate the best thickness for an antireflective coating for silicon wafers. Several depositions have been performed at different substrate temperatures. Photo conductive measurements by a WCT‐100 were performed on silicon wafer after each thermal process to measure the effective minority carrier lifetime of p‐type crystalline silicon wafer boron doped 〈100〉. Reflectance measurements were performed for samples prepared at different bias and flow gas ratios. Results show that the coating provides reflection reduction to levels below 5% for samples with a thickness of 70 nm. An increase in carrier lifetime has been observed for AlN deposited at high temperature. Annealing at 400 °C has been shown to increase carrier lifetime to 12 µs compared to 7 µs, suggesting the potential of AlN for silicon passivation and an alternative antireflective coating (ARC) to silicon nitride. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Passivation of solar cell emitters using aluminum nitride

“…1 Ω cm FZ, p-type also consistent with the low level of passivation reported by Kaminski [10]. Increasing the hydrogen flow leads to an increase in lifetime accompanied by a decrease of the interface defect density.…”

“…Recent experiments for reactively sputtered aluminum nitride in silicon photovoltaics reached only a low level of passivation with lifetimes of 12 µs [10]. It has been shown for sputtered SiN x :H that the hydrogen concentration in the layer can significantly influence the obtainable solar cell efficiency [12,18].…”

“…Due to the very low interface defect density, AlN:H is an appealing alternative material for the passivation of p + and n + surfaces. It has furthermore very interesting optical properties as the refractive index and the extinction coefficient are very similar to SiN x :H [2,10]. Using Al 2 O 3 as a passivation layer on the front of a solar cell, a capping layer of 75 nm of SiN x :H is needed to ensure good anti-reflective properties.…”

Study of hydrogenated AlN as an anti‐reflective coating and for the effective surface passivation of silicon

“…Previous attempts in the use of aluminum nitride for silicon solar cells resulted in good anti‐reflection coatings, but good surface passivation was not achieved 21. In the present contribution, we demonstrate that sputtered hydrogenated aluminum nitride can provide both excellent surface passivation and good anti‐reflection properties, making it a suitable alternative to the aluminum oxide and silicon nitride stack that is currently used in silicon solar cells.…”

Antireflective Coatings: Conventional Stacking Layers and Ultrathin Plasmonic Metasurfaces, A Mini-Review

“…Beside classical uniform single-layer ARCs, many structured or patterned films and surfaces have also been developed which exhibit very low reflection in a range of spectra. These designs include (but are not limited to) silica particles [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] (see Figure 1 c,d), silica particle-polymer hybrids [ 19 ], polymer particles [ 20 ] and films [ 21 ], composites (silica-Teflon [ 22 ], spirooxazine-doped polystyrene [ 23 , 24 ]), vinyltrimethoxy silane films [ 25 ], SiO 2 /TiO 2 particles [ 26 , 27 ], and TiO 2 film [ 28 ] and AlN x [ 29 ]. Although a single-layer (wavelength) ARC is desired in laser and photodiodes [ 30 ] and solar cells [ 31 ] the narrow band of the reflection dip makes it impractical for many applications such, eyeglasses and displays.…”