New clean energy technologies such as wind, solar, and electric cars have shown great potential to reduce emissions. It will be necessary to deploy these technologies at a much larger scale, alongside other technology solutions that are still in an early stage of development, such as hydrogen and carbon capture, to achieve net-zero emissions.  It is estimated that wind, solar, bioenergy, geothermal, and hydro energy will supply two-thirds of the world's energy supply in 2050 [1]. In the next 20 years, solar PV capacity will increase 20-fold, while wind power will increase 11-fold. Figure 1 shows the key clean technologies ramp up by 2030 in the net zero pathway.  

Fig1. Key clean technologies ramp up by 2030 in the net zero pathway [1]

By 2050, wind and solar PV will provide almost half of the world's energy(Fig2).  When a light strikes on a solar cell, it converts sunlight into electricity-producing electric power. Semiconductors are used as p–n junctions for photovoltaic energy conversion. Optical and electrical simulations are typically required when designing a solar cell. Ansys Lumerical  FDTD solver is used to simulate optical absorption. Thermal simulations can be run for this study to include heating effects as part of the device's performance.  Ansys Lumerical DEVICE is used to simulate electron-hole recombination during the electrical simulation.

 

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Fig 2. (a)  Global electricity generation by source in the APC (b) Global total final consumption by fuel in the NZE[1].

To improve the efficiency of solar cells,we will demonstrate  thin-film materials, III-V materials, organic materials, plasmonic materials, dye-sensitized materials, gratings, and photonic crystals using Lumerical tools. The rest of this document will show you how Ansys Lumerical can be used to simulate and optimise a variety of solar cells. 

Planar silicon solar cell:

Although thin-film solar cells have a relatively low efficiency compared to other structures, they have gained much interest because of their low manufacturing costs. Low absorption of Si at longer wavelengths is the main reason for poor efficiency.  In this example we're going to simulate a simple 1D planner silicon solar cell using Lumerical. The absorption can be calculated from electric field intensity and imaginary part of permittivity. Lumerical FDTD simulations can measure both parameters. 

You will learn how to define your geometry, insert your solver, and monitor your solar cell in Lumerical simulation of solar cells. As an example, we used solar generation analysis group covering the simulation region and FDTD region. Under solar illumination, this calculation calculates the electron-hole pair generation rate. Solar generation analysis group output properties are exported to Lumerical DEVICE as generation rate data, which facilitates electrical simulations. 

Fig 3 Planar silicon solar cell

For the inclusion of practical conditions, we also included non-idealities like silicon with bulk recombination and silicon with bulk and surface recombination in the simulated  structure. Finally, using Lumerical you can optimize short circuit current, efficiency, open circuit voltage, and fill factor of solar cells. Here is the workflow for simulatingsolar cells.

 

Fig 4 workflow for simulating solar cells

Learn how to simulate the solar cell using Lumerical in the following videos.

(1) Solar cells simulation - (Part1- Theory) - YouTube

(1) Solar cells simulation using Lumerical tools (Part2- Lumerical FDTD) - YouTube

(1) Solar cells simulation using Lumerical tools (Part3- Lumerical Heat) - YouTube

(1) Solar cells simulation using Lumerical tools (Part4- Lumerical Charge-setting) - YouTube

(1) Solar cells simulation using Lumerical tools (Part5- Lumerical Charge-(I_SC, V_OC, FF, Efficiency)) - YouTube

 

Plasmonic solar cell at normal and oblique incidence

Thin film solar cells have the potential to significantly decrease the cost of photovoltaics. However, it is critical to trap light in the solar cell to increase light absorption, i.e. to increase the conversion efficiency.

Using Lumerical, you can calculate solar parameters and find out how to improve light absorption into the active layer. For this purpose, nano-sized structures, such as textured surface and nano–particle deposition on the surface, have been proposed.

Using anti-reflective coatings and texturing reduces reflections and traps light within the cell, extending its optical path. Researchers found that plasmonic approaches increase light absorption the most effectively.

Among nanosized materials, silver, gold, and aluminum reflect most of the visible light and absorb most of the ultraviolet light, so energy loss is minimized, and efficiency is maximized. By creating localized surface plasmons due to the scattering effect, the absorption is increased, leading to a lower recombination rate, higher open-circuit voltage, and higher conversion efficiency, all of which are key performance parameters to design an efficient solar cell.

Fig. 5 Solar cell surface metal nanoparticles 

Follow this link to learn how to simulate a metal nanoparticle solar cell.

https://optics.ansys.com/hc/en-us/articles/360042156874

 

solar cell design using periodic structure

Since Si has an indirect band gap, a significant part of the near infrared radiation is not absorbed at this thickness. As a result, using very thin Si substrates reduces cost while increasing inefficiency. Thin Si cells require an efficient light-trapping scheme in order to avoid excessive optical losses. Adding a layer of periodic structure on top of the substrate minimizes large back reflections of solar radiation from solar cells. There is a potential for periodic structures to trap light better than random structures over a limited spectral range. Several studies have investigated periodic structures for light trapping in solar cells. 

 

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Fig. 6 (a) 2D silicon square grating solar cell (b) 3D pillar silicon solar cell (c) Silicon solar cell with TiO2 pyramid array (d) Silicon solar cell with moth-eye anti-reflection coatings

Click on the links below for more information about designing periodic structures.

https://optics.ansys.com/hc/en-us/articles/360042646593

https://optics.ansys.com/hc/en-us/articles/360042646053

https://optics.ansys.com/hc/en-us/articles/360042158434

https://optics.ansys.com/hc/en-us/articles/360042646833

 III-V Solar Panel

Maximizing efficiency is one of the major challenges of designing solar cells. In this example, you will learn how lumerical considers optical and electrical factors that reduce the efficiency of a single junction GaAs solar cell below Shockley-Queisser's theoretical limit.

Fig. 7   III-V Solar Panel

For more information, please click on the link below.

https://optics.ansys.com/hc/en-us/articles/360042160334

Organic solar cell with PC structure

In comparison with conventional silicon-based solar cells, organic solar cells (OSC) have a variety of advantages, including low cost and flexibility. For many practical applications, it is necessary to improve the low conversion efficiency. Studies have been conducted using nano-sized structures to improve the conversion efficiency by increasing light absorption. Using photonic crystal structures in the photoactive layer can enhance light absorption by trapping light as leaky modes within the structures.  In this part, you will learn how using Lumerical you can simulate the light absorption within the OSC with PC.

Fig. 8   Organic solar cell with PC structure

 

https://optics.ansys.com/hc/en-us/articles/360042157554

In summary, different kinds of solar cells can be simulated using Lumerical. It is possible to simulate the periodic structure, plasmonic properties, organic properties of solar cells, as well as to calculate and optimize their performance. 

[1] IEA (2021), Net Zero by 2050, IEA, Paris https://www.iea.org/reports/net-zero-by-2050, License: CC BY 4.0

Post by Majid Ebnali Heidari
January 12, 2023

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