Layered Solar Cell Technology: The Past, The Present, and The Future

Do you want to enjoy the tremendous benefits of solar energy for your home at an affordable price?

According to the International Energy Agency, solar energy could be the biggest source of electricity in the world by 2050. As of 2019, the solar PV market increased at around 115GW, which is about 12%.

Environmental pollution and energy consumption are on the increase throughout the world, making it challenging for traditional fossil energy sources to meet the demands for sustainable development of human society.

What can be done about this?

With one of the prerequisites for the development of human society being the utilization of renewable, clean energy sources, there is a need to create new energy technologies to serve the needs of consumers.

Of all the new energy technologies that are introduced daily, solar power has stood out as one of the best.

A rapid growth is apparent in the solar technology industry, caused by the increasing number of people opting to install photovoltaic systems. This is an excellent time to join the trend by investing in the high-quality solar technologies offered by Enlightened Solar.

Here is an overview of this article:

  • A brief history of solar cells and how they are made
  • What are solar cell technologies?
  • What are Perovskite/Silicon Tandem solar cells?
  • How are perovskite solar cells layered on silicon solar cells?
  • The impact of layered solar cell technology on solar panel efficiency
  • The secret formula for a more affordable layered solar cell technology
  • The future of solar power

Let’s take a quick look at how solar cells came about…

A Brief History of Solar Cells and How They Are Made

Solar cells are among the biggest sustainable energy methods that can convert radiated light from the sun into electricity.

But how did solar cells come about in the first place?

The first silicon solar cell was produced by a Bell Laboratories physicist called Gerald Pearson in 1953. His research was refined by Daryl Chapin and Calvin Fuller, who were also Bell researchers. They created the solar cell to convert enough energy from the sun and apply it to electrical equipment.

The sun provides about 107W of energy to the Earth, but this figure reduces by 30% after passing through the Earth’s atmosphere. Solar cells and the sun work hand-in-hand to provide a sustainable alternative to the energy and resource problems facing the power industry today.

Solar cells have a positive impact on the Earth, including:

  • The preservation of natural resources
  • A reduction in the amount of energy required for consumption
  • The provision of clean air by not emitting greenhouse gases
  • The provision of a reliable source of electricity for home and industrial use
  • The generation of economic activity
  • A reduction in rural depopulation

The solar cells in each panel consist of 4 key materials, namely:

  • Monocrystalline cells
  • Polycrystalline solar cells
  • Thin-film solar cells

What does the manufacturing process of solar cells involve?

Before solar cells are made, they have to pass through the following 7 stages:

  • Purification of the silicon
  • Production of the single-crystal silicon
  • Making the silicon wafers

  • Doping
  • Placing the electrical contacts
  • Adding the anti-reflective coating
  • Encapsulating the cell

What Are Solar Cell Technologies?

Solar cells or photovoltaic cells (PV) generate electricity from sunlight through a process known as the photovoltaic effect. The photovoltaic cells are electrically connected and neatly arranged into a large frame called the solar panel.

Currently, the solar cells in use are made from silicon semiconductors that absorb sunlight, converting it into electricity. Solar panels convert only about 20% of the sunlight they receive into electricity.

Is silicon the only form of solar cells available today?

Other forms of solar cells are available for both commercial and industrial purposes, but despite an efficiency rating of up to 40%, they are far more expensive than domestic models.

Advances in solar technology are made constantly to raise the overall efficiency and quality while ensuring a reduction in the price of solar panels. This is becoming possible with further research and development in the field.

Hence the development of Perovskite/Silicon tandem solar cells!

What Are Perovskite/Silicon Tandem Solar Cells?

Perovskite/Si tandem solar cells offer significant benefits, including the potential to surpass conventional solar cells.

Perovskite materials are obtained from calcium titanate compounds and have attracted considerable attention due to their cubic lattice-nested octahedral layered structures, as well as their unique thermal, optical, and electromagnetic properties.

The perovskite materials that are used in solar cells comprise a type of organic-inorganic metal halide compound with a perovskite structure.

Advances in perovskite solar cells consist of the following layers:

  • The perovskite light-absorbing layer
  • The electron transport layer
  • The hole transport layer
  • Solar cells without a hole transport layer

How Are Perovskite Solar Cells Layered on Silicon Solar Cells?

As far as the solar power industry is concerned, silicon solar cells have been used as the go-to standard product. For many years, these silicon-based solar cells could only convert between 18% and 21% of solar energy into useful electricity. They top-out this average at around 26.6%.

This means that the cost of installing the cells exceeded the cost of buying them.

What are researchers doing to help?

In a bid to increase the efficiency of solar cells, researchers layered the perovskite solar cell, which is a crystal structure that collects higher energy photons, on the silicon solar cell, capturing photons in infrared light.

When combined, these two solar cells can exhibit an efficiency of up to 27%. This is a one-third increase from silicon solar cells’ efficiency of 21%.

The Impact of Layered Solar Cell Technology on Solar Panel Efficiency

Despite how far solar cells have come, thin-film solar cells, though inexpensive, are still lagging far behind the more expensive crystalline solar cells in terms of efficiency.

The efficiency of solar panels, when using layered solar cell technology, shows a dramatic improvement.

How is this possible?

Solar cells tend to lose some of their conversion potential when they are distributed over a large surface area, like a solar panel. This makes the average efficiency of the solar panel lower than the actual maximum.

What this means is that, before you can achieve higher efficiency levels, you must install more solar panels and link them together to form an array. Consequently, this will lead to an increase in the overall cost.

However, when a perovskite solar cell is layered on top of a silicon solar cell, there will be a dramatic improvement in the overall efficiency of the solar panels. Additionally, there will be no need to install as many solar panels to get more power.

A team of researchers led by Akhlesh Lakhtakia, suggest that if two thin films made from different materials are used, it is possible to create thin-film cells that are affordable and have an efficiency of about 34%.

This research revealed that most researchers approach solar cells from the optical and electrical perspectives. The optical side shows how the light from the sun is collected, while the electrical side shows how the sunlight that is collected is converted into electricity.

Lakhtakia, being a theoretician, created a mathematical model that treated both the electrical and optical aspects equally. In his opinion, “we needed to increase actual efficiency because if the efficiency of a cell is less than 30% it isn’t going to make a difference.”

He explained that solar cells are not very complex devices. The clear top layer makes it possible for the sunlight to reach the layer that converts the energy. The material used to convert this energy absorbs the light, producing streams of positively charged holes and negatively charged electrons moving in opposite directions.

These differently charged particles are then transferred to a contact layer on the top and bottom contact layers, helping to channel the electricity to the outside of the cell so it can be used. Meanwhile, the amount of energy produced by a cell depends solely on the amount of sunlight collected, as well as how well the conversion layer works.

According to Lakhtakia, “I realized that to increase efficiency we had to absorb more light. To do that we had to make the absorbent layer nonhomogeneous in a special way.”

The special way he was referring to was to use 2 different absorbent materials in 2 different thin films. This was done because different materials react in various ways to different wavelengths of light and also convert them differently.

So, for the layers, researchers chose Copper Indium Gallium Diselenide (CIGS), which is commercially available, and Copper Zinc Tin Sulfur Selenide (CZTSSe). Individually, CIGS has an efficiency of about 20%, while CZTSSe’s efficiency is about 11%.

These two materials have the same structure so they can work in a solar cell. Because their lattice structure is roughly the same, they can be grown on top of each other. Also, because they absorb different frequencies of the spectrum, they should be able to increase efficiency.

Together, both materials produced a solar cell that was 34% efficient. This, according to Lakhtakia, creates a new layer-upon-layer solar cell architecture. He believes other formulations of layers can also work, probably even more efficiently.

The Secret Formula For A More Affordable Layered Solar Cell Technology

Researchers have been trying to improve the efficiency of solar energy for a long time, by layering solar cells.

As far back as the 1970s, tandem solar cells, also known as multi-junction solar cells, were developed that could achieve almost 50% efficiency. Unfortunately, these solar cells are very expensive to manufacture and can cost as much as $80,000 per square meter because the cells have to be grown one layer at a time to create a big, single crystal.

Can the average homeowner or business owner afford this?

No!

The CU Boulder research team, pioneered by McGehee and his fellow researchers, took a different approach in creating solar cells at a very affordable price, while exhibiting one of the highest power-conversion efficiencies.

The process, which is referred to as the “secret formula” by Michael McGehee, uses a unique triple-halide alloy consisting of chlorine, bromine, and iodine.

Less than 10 years ago, they started by using materials that were less expensive on top of the silicon. At first, they could only achieve an efficiency level of about 13%. Technological improvements have made it possible for them to double that number.

According to McGehee, there is an ideal bandgap in solar cells. This bandgap is the space that lies between energy levels inside a semiconductor. Electrons jump between this space to create electrical energy.

When they used bromine, the bandgap increased. Then they used bromine with iodine and exposed them to light, but the elements were not always stable.

In previous studies, chlorine and iodine were used together, but the difference in their particle sizes did not allow enough chlorine to fit into the structure of the perovskite crystal.

The researchers then used different amounts of bromine, chlorine, and iodine to shrink the crystal structure and allow more chlorine to enter. This helped to stabilize and improve the efficiency of the cell.

Also, perovskites are not expensive and do not require too much energy to make. So, it is easy to produce them in the laboratory. These new solar cells only showed minimal changes in their first level of efficiency even after testing them with intensive light and heat for almost 42 days or 1,000 hours.

Since solar power marketing is growing at an annual rate of about 30%, new technologies will have to satisfy three major considerations before they can become mainstream.

What are these considerations?

They are:

  • Efficiency
  • Cost
  • Longevity

McGehee is very optimistic about what the future holds for this layered perovskite solar cell with its wide-bandgap. In addition to surpassing the maximum efficiency of a silicon solar cell, he said “we believe it can take us over 30% efficiency and that it can be stable.”

The Future of Solar Power

Are you finding it difficult to afford solar power?

The commercial products that are currently used to generate solar power, mainly silicon and thin-film based technologies, are processed using vacuum-based techniques, thereby making them expensive.

Thanks to the newly discovered nanotube structure that can transport electrical charges up to 100 million times higher than was previously measured, the next-generation solar cells may have infinite uses.

Currently, most solar cells use silicon to absorb light. But because the material is inefficient, scientists have developed layered solar cell technologies that can enhance the light absorption capability of the current cells.

Since nanotubes are difficult to arrange within the solar cells, a new generation of perovskite solar panels has been introduced with the potential to cost-efficiently convert solar energy into electricity for household use. They will be more than 50% more efficient and 40% cheaper than the commercially produced ones we are using today.

Solar panels made from perovskite can absorb most of the solar spectrum while being operable in various atmospheric conditions instead of working in direct sunlight alone.

These perovskite materials have been tested in the United States, Europe, Asia, and the Middle East. Since perovskite panels go through a very straightforward production process, researchers still need to better understand its properties by testing the material under various conditions.

When this is done, companies will begin an industrial-scale production that the average homeowner can afford without breaking the bank.

So, what is the way forward for an average homeowner?

Is a solar cell technology with an efficiency of more than 30% possible?

Definitely! Efficient solar cells are, no doubt, the key to affordable, renewable electricity.

At Enlightened Solar, we provide a market, a more reliable, and natural way to power everything in our lives. Give us a call and we will help you to become energy-independent.