Improverment of electrical and optical properties of doped amorphous silicon layers applied to heterojunction solar cells

The optimisation of electrical and optical properties of doped amorphous silicon layers (the emitter layer) is the key importance to obtain high efficiency heterojunction (HJ) solar cells. Desired properties for the emitter layer include wide bandgap, low surface and interface recombination, and good doping efficiency. In this study, we report the thinfilm properties of n-doped nc-Si:H emitter layers deposited using RF (13.56 MHz) PECVD, at different SiH4/H2 gas flow ratios, at the same RF power, pressures, and temperatures. Trends relating deposition conditions to relevant film characteristics such as thickness, wide bandgap, crystalline fraction and conductivity are discussed. Finally, the heterojunction solar cells using the optimised parameters for n-doped nc- Si:H layers are fabricated with high short circuit current (17 mA).

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17.8%-efficient Amorphous Silicon Heterojunction Solar Cells on p-type Silicon Wafers

MRS Proceedings ◽

10.1557/proc-0910-a26-05 ◽

2006 ◽

Vol 910 ◽

Cited By ~ 2

Author(s):

Qi Wang ◽

Matt P. Page ◽

Eugene Iwancizko ◽

Yueqin Xu ◽

Yanfa Yan ◽

...

Keyword(s):

Solar Cells ◽

Solar Cell ◽

Amorphous Silicon ◽

High Efficiency ◽

Short Circuit ◽

Open Circuit ◽

Layer Growth ◽

Surface Recombination Velocity ◽

Back Contact ◽

P Type

AbstractWe have achieved an independently-confirmed 17.8% conversion efficiency in a 1-cm2, p-type, float-zone silicon (FZ-Si) based heterojunction solar cell. Both the front emitter and back contact are hydrogenated amorphous silicon (a-Si:H) deposited by hot-wire chemical vapor deposition (HWCVD). This is the highest reported efficiency for a HWCVD silicon heterojunction (SHJ) solar cell. Two main improvements lead to our most recent increases in efficiency: 1) the use of textured Si wafers, and 2) the application of a-Si:H heterojunctions on both sides of the cell. Despite the use of textured c-Si to increase the short-circuit current, we were able to maintain the same 0.65 V open-circuit voltage as on flat c-Si. This is achieved by coating a-Si:H conformally on the c-Si surfaces, including covering the tips of the anisotropically-etched pyramids. A brief atomic H treatment before emitter deposition is not necessary on the textured wafers, though it was helpful in the flat wafers. It is essential to high efficiency SHJ solar cells that the emitter grows abruptly as amorphous silicon, instead of as microcrystalline or epitaxial Si. The contact on each side of the cell comprises a thin (< 5 nm) low substrate temperature (~100°C) intrinsic a-Si:H layer, followed by a doped layer. Our intrinsic layers are deposited at 0.3-1.2 nm/s. The doped emitter and back-contact layers were deposited at a higher temperature (>200°C) and grown from PH3/SiH4/H2 and B2H6/SiH4/H2 doping gas mixtures, respectively. This combination of low (intrinsic) and high (doped layer) growth temperatures was optimized by lifetime and surface recombination velocity measurements. Our rapid efficiency advance suggests that HWCVD may have advantages over plasma-enhanced (PE) CVD in fabrication of high-efficiency heterojunction c-Si cells; there is no need for process optimization to avoid plasma damage to the delicate, high-quality, Si wafers.

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p-type nc-SiOx:H emitter layer for silicon heterojunction solar cells grown by rf-PECVD

MRS Proceedings ◽

10.1557/opl.2015.552 ◽

2015 ◽

Vol 1770 ◽

pp. 7-12 ◽

Cited By ~ 1

Author(s):

Henriette A. Gatz ◽

Yinghuan Kuang ◽

Marcel A. Verheijen ◽

Jatin K. Rath ◽

Wilhelmus M.M. (Erwin) Kessels ◽

...

Keyword(s):

Solar Cells ◽

Amorphous Silicon ◽

Material Properties ◽

Crystalline Silicon ◽

Silicon Layer ◽

Nanocrystalline Silicon ◽

Emitter Layer ◽

Heterojunction Solar Cells ◽

P Type ◽

Silicon Heterojunction Solar Cells

ABSTRACTSilicon heterojunction solar cells (SHJ) with thin intrinsic layers are well known for their high efficiencies. A promising way to further enhance their excellent characteristics is to enable more light to enter the crystalline silicon (c-Si) absorber of the cell while maintaining a simple cell configuration. Our approach is to replace the amorphous silicon (a-Si:H) emitter layer with a more transparent nanocrystalline silicon oxide (nc-SiOx:H) layer. In this work, we focus on optimizing the p-type nc-SiOx:H material properties, grown by radio frequency plasma enhanced chemical vapor deposition (rf PECVD), on an amorphous silicon layer.20 nm thick nanocrystalline layers were successfully grown on a 5 nm a-Si:H layer. The effect of different ratios of trimethylboron to silane gas flow rates on the material properties were investigated, yielding an optimized material with a conductivity in the lateral direction of 7.9×10-4 S/cm combined with a band gap of E04 = 2.33 eV. Despite its larger thickness as compared to a conventional window a-Si:H p-layer, the novel layer stack of a-Si:H(i)/nc-SiOx:H(p) shows significantly enhanced transmission compared to the stack with a conventional a-Si:H(p) emitter. Altogether, the chosen material exhibits promising characteristics for implementation in SHJ solar cells.

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Simulation of InAIN/Si Single-Heterojunction Solar Cells Using wxAMPS

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.665.111 ◽

2014 ◽

Vol 665 ◽

pp. 111-114 ◽

Cited By ~ 1

Author(s):

Ying Huang ◽

Xiao Ming Shen ◽

Xiao Feng Wei

Keyword(s):

Solar Cells ◽

Fill Factor ◽

High Efficiency ◽

Open Circuit Voltage ◽

Short Circuit ◽

Short Circuit Current ◽

Indium Content ◽

Open Circuit ◽

Heterojunction Solar Cells ◽

Si Solar Cells

In this paper, InAlN/Si single-heterojunction solar cells have been theoretically simulated based on wxAMPS software. The photovoltaic parameters, such as open circuit voltage, short circuit current, fill factor and conversion efficiency were investigated with changing the indium content and thickness of n-InAlN layer. Simulation results show that the optimum efficiency of InAlN/Si solar cells is 23.1% under AM 1.5G spectral illuminations, with the indium content and thickness of n-InAlN layer are 0.65 and 600nm, respectively. The simulation would contribute to design and fabricate high efficiency InAlN/Si solar cells in experiment.

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