Fabrication and simulating solar cell devices using silvaco tcad tools

Innovative Systems Design and Engineering www.iiste.org
ISSN 2222-1727 (Paper) ISSN 2222-2871 (Online)
Vol.4, No.7, 2013 - National Conference on Emerging Trends in Electrical, Instrumentation & Communication Engineering
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Fabrication and Simulating Solar Cell Devices using Silvaco
TCAD Tools
Anand Kumar Srivastava (M.Tech VLSI Design)
Hindustan College of Science and Technology, Farah, Mathura.
E-mail: anandsrivas@gmail.com
Sanjay Singh Chahar
Electronics & Instrumentation Engineering Department, Anand Engineering College, Agra
E-mail: sanjayaec@rediffmail.com
Abstract
Solar cells are p-i-n photodiodes, which are operated under forward bias. The intention is to convert the
incoming optical power into electrical power with maximum efficiency.
In this paper we are going to design a solar cell and simulation of solar cell using the Silvaco TCAD tools.
Silvaco TCAD refers to Technology Computer-Aided Design. This means that computer simulations are used to
develop and optimize semiconductor processing technologies and devices. As TCAD simulations solve
fundamental, physical partial differential equations, such as Poisson, Diffusion and Transport equations in a
semiconductor device. This deep physical approach gives TCAD simulation predictive accuracy. It is therefore
possible to substitute TCAD simulations for costly and time-consuming test wafer runs when developing and
characterizing a new semiconductor device or technology.
Keywords- photodiode, Silvaco TCAD Tools.
1. INTRODUCTION
Silvaco TCAD offers complete and well integrated simulation software for all aspects of solar cell technology.
CAD modules required for Solar Cell simulation include: S-Pisces, Blaze, Luminous, TFT, Device3D,
Luminous3D and TFT3D [1]. The TCAD Driven CAD approach provides the most accurate models to device
engineers. Silvaco is the one-stop vendor for all companies interested in advanced Solar Cell technology
simulation Solutions.
2. TCAD MODULES FOR SOLAR CELL TECHNOLOGY SIMULATION
Brief descriptions of the TCAD modules that can be used for solar cell technology simulation are listed below.
For more details of these modules, please visit the Silvaco TCAD products.
S-Pisces is an advanced 2D device simulator for silicon based technologies that incorporates both drift-diffusion
and energy balance transport equations. Large selections of physical models are available for solar cell
simulation which includes surface/bulk mobility, recombination, impact ionization and tunneling models.
Blaze simulates 2D solar cell devices fabricated using advanced materials. It includes a library of binary, ternary
and quaternary semiconductors. Blaze has built-in models for simulating state-of-the-art multi-junction solar cell
devices.Device3D is a 3D device simulator for silicon and other material based technologies. The DC, AC and
time domain Characteristics of a wide variety of silicon, III-V, II-VI and IV-IV devices are analyzed.
Luminous and Luminous3D are advanced 2D and 3D simulator specially designed to model light absorption and
photo generation in non-planar Solar Cell devices. Exact solutions for general optical sources are obtained using
geometric ray tracing. This feature enables Luminous and Luminous3D to account for arbitrary topologies,
internal and external reflections and refractions, polarization dependencies and dispersion. Luminous and
Luminous3D also allows optical transfer matrix method analysis for coherence effects in layered devices. The
beam propagation method may be used to simulate coherence effects and diffraction.
TFT and TFT3D are advanced 2D and 3D device technology simulators equipped with the physical models and
specialized numerical techniques required to simulate Spectral Response of a Solar Cell. Amorphous or
polycrystalline devices including thin film transistors. TFT and TFT3D can be used with Luminous and
Luminous3D to simulate thin film solar cells made from amorphous silicon. Spectral, DC and transient responses
can be extracted.
3. SIMULATING OF SOLAR CELL CHARACTERISTICS
Here, we will discuss the various aspects of solar cell characteristics that can be simulated by Silvaco
TCADTools. Typical characteristics include collection efficiency, spectral response, open circuit voltage, VOC
and short Circuit current ISC. The simulated spectral response of a solar cell using the luminous module. This

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figure1 is obtained by varying the incident wavelength of a light source to extract the solar cell’s spectral
response.
From this figure 1, the green curve is the equivalent current from the light source; the red curve is the available
photo current generated by the light within the solar cell device and the blue curve is the actual terminal current.
Collection efficiency including the effects of reflection can be calculated by the ratio of these quantities.
It is possible to study the details of photo generation of carriers in the solar cell device during light illumination.
This is very useful for simulation of multi-junction devices. Contour plot of photo generation rate in a simple
thin film amorphous silicon solar cell. Note that in this figure, the device has an opaque metal contact in the
center of the structure. Once photo generation rates are obtained, terminal currents can be evaluated to determine
the quantum efficiency of the solar cell. One useful feature of the luminous module is ray tracing. This feature
enables the analysis of more advanced solar cells designs. Besides studying the photo generation rates due to a
normal incident light beam, the photo generation rates due to an angled light beam can also be studied. The
photo generation in a silicon solar cell when light impinges on the cell which has pyramids on the surface. From
this figure, it can be seen that the light path inside the semiconductor is diverted from its original path due to the
pyramid surface. This causes the contour of the photo generation rates to be a saw-tooth shape as shown in the
right hand photo generation Rate from Angled Light Beam. Photo generation Contours in Amorphous Silicon
Once the photo generation rates are obtained by the Luminous module, ATLAS will then be able to simulate the
terminal currents to obtain the IV characteristics. The IV characteristics of an amorphous silicon solar cell under
AM0 illumination. In this figure, ISC is the short circuit current and VOC is the open circuit voltage. The ISC is
extracted from the curve when the voltage is zero. On the other hand, the VOC can be extracted from the IV
curve when the current is zero. Also, the maximum current, Im and maximum voltage, Vm, can be obtained from
the maximum power rectangle as indicated in the figure. By changing the illumination power of the light beam,
we can obtain a series of IV characteristics as a function of the illumination power can be obtained.. From this
figure, it can be seen that the short circuit current increase linearly with the increase of light power, where the
open circuit voltage begins to saturate with the increase of light power.
4. CONCLUSION
In conclusion, Silvaco TCAD tools provide a complete solution for researchers interested in solar cell
technology. It enables researchers to study the electrical properties of solar cells under illumination in both Two-
and Three dimensional domains. The simulated properties include IV characteristics, spectral response, quantum
efficiency, photo generation rates, potential distribution, etc. In addition, the software is also capable of
simulating amorphous silicon solar cell devices and large area solar cells with texture surfaces. Silvaco is the
one-stop vendor for all companies interested in advanced solar cell technology simulation solutions.
5. References
“ATLAS User’s Manual ”, Silvaco, Santa Clara, California, USA.
Silvaco ATLAS website: http :/www.silvaco.com/ products/device_simulation/atlas.html
“ATHENA User’s Manual ”, Silvaco, Santa Clara, California, USA.
Figure 1: Si based solar cell Fabrication and Simulation Result

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Figure 2: Spectral Response of a Solar Cell
Figure 3: Photo generation Contours in Amorphous Silicon Solar Cell Device

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Figure 4: Current Voltage Characteristics of Amorphous Silicon Solar Cell Device
Figure 5: Photo generation Rate from Angled Light Beam

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