Assessment of Intrinsic-Layer Growth Temperature to High-Deposition-Rate a-Si:H n-i-p Solar Cells Deposited by Hot-Wire CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
Qi Wang ◽  
Eugene Iwaniczko ◽  
Yueqin Xu ◽  
Brent P. Nelson ◽  
A. H. Mahan
Keyword(s):  
Solar Cells ◽  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Diffusion Length ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Ambipolar Diffusion ◽  
Hot Wire ◽  
Top Contact ◽  
Hydrogenated Amorphous

AbstractWe report progress in hydrogenated amorphous silicon n-i-p solar cells with the i-layer grown by the hot-wire chemical vapor deposition technique. Early research showed that we grew device-quality materials with low saturated defect density (2 × 106/cm3), high initial ambipolar diffusion length (~2000 Å) and low hydrogen content (<1%). One of the major barriers to implementing this material into solar cells is the high substrate temperature required (>400°C). We re-assess the effects of low substrate temperature on the property of the films and the performance of the solar cells as an alternative avenue to solving this problem. We find that the material grown at 300°C can have similar values of saturated defect density and ambipolar diffusion length as the one grown greater than 400°C. We also study the effect of i-layer substrate temperature ranging from 280° to 440°C for n-i-p solar cells. We now consistently grow devices with Fill Factor (FF) greater than 0.66, with the best close to 0.70 at lower substrate temperature. A collaboration with United Solar System, in where they grew the p-layer and top contact, produced devices with initial efficiencies as high as 9.8%. We produce n-i-p solar cells with initial efficiencies as high as 8% when we grow all the hydrogenated amorphous silicon and top contact layers. All these i-layers are grown at deposition rates of 16 to 18 Å/sec. We need to further improve our p-layer and transparent conductor layer to equal the collaborative cell efficiency. We also report light-soaking results of these devices.

Low Hydrogen Content, High Quality Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD

1999 ◽  
Vol 557 ◽  
Author(s):  
Brent P. Nelson ◽  
Richard S. Crandall ◽  
Eugene Iwaniczko ◽  
A. H. Mahan ◽  
Qi Wang ◽  
...  
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Hydrogen Content ◽  
Defect Density ◽  
Flow Direction ◽  
Scale Up ◽  
Hydrogenated Amorphous Silicon ◽  
Hot Wire ◽  
High Quality ◽  
Hydrogenated Amorphous

AbstractWe grow hydrogenated amorphous silicon (a-Si:H) by Hot-Wire Chemical Vapor Deposition (HWCVD). Our early work with this technique has shown that we can grow a-Si:H that is different from typical a-Si:H materials. Specifically, we demonstrated the ability to grow a-Si:H of exceptional quality with very low hydrogen (H) contents (0.01 to 4 at. %). The deposition chambers in which this early work was done have two limitations: they hold only small-area substrates and they are incompatible with a load-lock. In our efforts to scale up to larger area chambers—that have load-lock compatibility—we encountered difficulty in growing high-quality films that also have a low H content. Substrate temperature has a direct effect on the H content of HWCVD grown a-Si:H. We found that making dramatic changes to the other deposition process parameters—at fixed substrate temperature and filament-to-substrate spacing—did not have much effect on the H content of the resulting films in our new chambers. However, these changes did have profound effects on film quality. We can grow high-quality a-Si:H in the new larger area chambers at 4 at. % H. For example, the lowest known stabilized defect density of a-Si:H is approximately 2 × 1016 cm-3, which we have grown in our new chamber at 18 Å/s. Making changes to our original chamber—making it more like our new reactor—did not increase the hydrogen content at a fixed substrate temperature and filament-to-substrate spacing. We continued to grow high quality films with low H content in spite of these changes. An interesting, and very useful, result of these experiments is that the orientation of the filament with respect to silane flow direction had no influence on film quality or the H content of the films. The condition of the filament is much more important to growing quality films than the geometry of the chamber due to tungsten-silicide formation on the filament.

scholarly journals Numerical Design of Ultrathin Hydrogenated Amorphous Silicon-Based Solar Cell

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
F. X. Abomo Abega ◽  
A. Teyou Ngoupo ◽  
J. M. B. Ndjaka
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Amorphous Silicon ◽  
Buffer Layer ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Theoretical Work ◽  
Silicon Based ◽  
The Impact ◽  
Hydrogenated Amorphous

Numerical modelling is used to confirm experimental and theoretical work. The aim of this work is to present how to simulate ultrathin hydrogenated amorphous silicon- (a-Si:H-) based solar cells with a ITO BRL in their architectures. The results obtained in this study come from SCAPS-1D software. In the first step, the comparison between the J-V characteristics of simulation and experiment of the ultrathin a-Si:H-based solar cell is in agreement. Secondly, to explore the impact of certain properties of the solar cell, investigations focus on the study of the influence of the intrinsic layer and the buffer layer/absorber interface on the electrical parameters ( J SC , V OC , FF, and η ). The increase of the intrinsic layer thickness improves performance, while the bulk defect density of the intrinsic layer and the surface defect density of the buffer layer/ i -(a-Si:H) interface, respectively, in the ranges [109 cm-3, 1015 cm-3] and [1010 cm-2, 5 × 10 13  cm-2], do not affect the performance of the ultrathin a-Si:H-based solar cell. Analysis also shows that with approximately 1 μm thickness of the intrinsic layer, the optimum conversion efficiency is 12.71% ( J SC = 18.95   mA · c m − 2 , V OC = 0.973   V , and FF = 68.95 % ). This work presents a contribution to improving the performance of a-Si-based solar cells.

scholarly journals Hot wire deposited hydrogenated amorphous silicon solar cells

1996 ◽  
Author(s):  
A. H. Mahan ◽  
B. P. Nelson ◽  
E. Iwaniczko ◽  
Q. Wang ◽  
E. C. Molenbroek ◽  
...  
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Solar Cells ◽  
Hot Wire ◽  
Hydrogenated Amorphous

Saturation behavior of the light-induced defect density in hydrogenated amorphous silicon (solar cells)

2002 ◽  
Author(s):  
H.R. Park ◽  
J.Z. Liu ◽  
P. Roca i Cabarrocas ◽  
A. Maruyama ◽  
M. Isomura ◽  
...  
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Silicon Solar Cells ◽  
Hydrogenated Amorphous

Deposition of Device Quality Amorphous Silicon by Hot-Wire CVD

1997 ◽  
Vol 467 ◽  
Author(s):  
K. F. Feenstra ◽  
C. H. M. Van Der Werf ◽  
E. C. Molenbroek ◽  
R. E. I. Schropp
Keyword(s):  
Growth Rate ◽  
Electrical Properties ◽  
Amorphous Silicon ◽  
Diffusion Length ◽  
Hydrogenated Amorphous Silicon ◽  
Dark Conductivity ◽  
Hot Wire ◽  
Tungsten Filaments ◽  
Wire Method ◽  
Hydrogenated Amorphous

ABSTRACTIn this paper we present the results of the optimization of hydrogenated amorphous silicon films deposited by the hot-wire method in a larger area system. Using a two-wire design, we succeeded in depositing films that exhibit uniform electrical properties over the whole 4” x 4” Corning 7059 glass substrate. At a substrate temperature of 430 °C. and a pressure of 20 μbar we obtained a growth rate of ∼2 nm/s. The temperature of the tungsten filaments was kept at 1850 °C. The values for the photoconductivity and dark conductivity were 8.9×10−6 S/cm and 1.6×10−10 S/cm respectively, whereas the ambipolar diffusion length, as measured with the Steady-State Photocarrier Grating technique (SSPG), amounted to 145 nm. This value is higher than for our device quality glow-discharge (GD) films, which yield devices with efficiencies higher than 10%. The hydrogen content was 9.5%.We report on the density-of-states (DOS) distribution in the films, which was measured with the techniques of Thermally Stimulated Conductivity (TSC) and Constant Photocurrent Method (CPM). Furthermore, we describe the behavior of the electrical properties on light-induced degradation. Finally, we incorporated these films in solar cells, using conventional GD doped layers. Preliminary SS/n-i-p/ITO devices yielded efficiencies in excess of 3% under 100 mW/cm2 AM 1.5 illumination. Further work concerning the optimization of the interfaces is in progress.

Hydrogenated Amorphous Silicon Grown by Hot-Wire CVD at Deposition Rates up to 1 µm/minute

2000 ◽  
Vol 609 ◽  
Author(s):  
Brent P. Nelson ◽  
Yueqin Xu ◽  
A. Harv Mahan ◽  
D.L. Williamson ◽  
R.S. Crandal
Keyword(s):  
Amorphous Silicon ◽  
Deposition Rate ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Conductivity Ratio ◽  
Hot Wire ◽  
Single Filament ◽  
Deposition Rates ◽  
X Ray ◽  
Hydrogenated Amorphous

ABSTRACTWe grow hydrogenated amorphous-silicon (a-Si:H) by the hot-wire chemical vapor deposition (HWCVD) technique. In our standard tube-reactor we use a single filament, centered 5 cm below the substrate and obtain deposition rates up to 20 Å/s. However, by adding a second filament, and decreasing the filament-to-substrate distance, we are able to grow a-Si:H at deposition rates exceeding 167 Å/s (1 µm/min). We find the deposition rate increases with increasing deposition pressure, silane flow rate, and filament current and decreasing filament-tosubstrate distance. There are significant interactions among these parameters that require optimization to grow films of optimal quality for a desired deposition rate. Using our best conditions, we are able to maintain an AM1.5 photoconductivity-to-dark-conductivity ratio of 105 at deposition rates up to 130 Å/s, beyond which the conductivity ratio decreases. Other electronic properties decrease more rapidly with increasing deposition rate, including the ambipolar diffusion length, Urbach energy, and the as-grown defect density. Measurements of void density by small-angle X-ray scattering (SAXS) reveal an increase by well over an order of magnitude when going from one to two filaments. However, both Raman and X-ray diffraction (XRD) measurements show no change in film structure with increasing deposition rates up to 144 Å/s, and atomic force microscopy (AFM) reveals little change in topology.

Sign in / Sign up

Export Citation Format

Share Document