Tandem solar cell - the next high-efficiency solution



Today, we will introduce a type of solar battery called a "tandem solar cell." Tandem solar cells are made by superimposing different materials so that both longer and shorter wavelengths of light can be effectively absorbed.


In this way, several continuous segments of the solar spectrum are covered, which can maximize the conversion of light energy into electrical energy.

1. What is a tandem solar cell

Photovoltaic cell BC is a back contact technology, and "tandem" usually refers to stacking two or more solar cells with different bandgap materials to form multi-junction solar cells to improve photoelectric conversion efficiency.

The sunlight spectrum can be divided into several continuous parts, with different bands corresponding to different materials. and stacked from outside to inside in order of the width of the band gap from the largest to the smallest.

Let the light with the shortest wavelength be used by the outermost wide bandgap material battery, and the light with a longer wavelength can be transmitted to the narrower bandgap material battery.

What is a tandem solar cell


This makes it possible to maximize the conversion of light energy into electrical energy, and cells with such a structure are tandem solar cells. The larger the number of layers of a tandem cell, the more adaptable the cell is to changes in the solar spectrum.

2. Three main types of tandem solar cells

  • Multi-compound tandem solar cell

GaInP2 material can be used as the top layer of tandem solar cell. The conversion efficiency of mature industrial products is about 23.1%, and it is gradually used as a power supply for satellites and other spacecraft, and the prospect is very broad. However, due to its high cost, it is difficult to produce in large quantities.

  • Amorphous silicon tandem solar cell

Although amorphous silicon based has a high absorption coefficient of sunlight and greatly reduces the demand for materials, it also has an obvious disadvantage: efficiency is reduced after a long period of sunlight.

The combination of tandem solar cell can effectively improve the stability of amorphous silicon, and reduce the efficiency degradation rate of outdoor sunlight for 1 year from 25% to 35% to less than 20%.

Three main types of tandem solar cells

  • Dye-sensitized tandem solar cell

The new tandem dye-sensitized solar cells have the characteristics of high photoelectric conversion efficiency, low price, simple preparation process and easy large-scale production.

It solves the problems of low efficiency, high cost and complex preparation process of existing solar cells. The dye-sensitized solar cells fabricated by the technical method of the invention can be used as photovoltaic power generation system and solar hydrogen production systems.

3. Analysis of the advantages of tandem solar cell

  • More efficient use of the solar spectrum

Different semiconductor materials have different absorption properties for the spectrum. By combining different materials, tandem cells can absorb sunlight in short- and long-wave moieties, respectively, thus achieving a higher theoretical energy conversion efficiency than single-material cells.

  • Enhanced charge separation and collection

Each layer of the 12 volt 200ah lithium battery is responsible for absorbing only its most efficient photon energy range, and the resulting electron-hole pairs are efficiently collected by the electrodes in their respective layers, reducing recombination losses.

Analysis of the advantages of tandem solar cell

  • Push the limits of single-junction efficiency

The theoretical upper limit of the theoretical efficiency of traditional single-junction silicon-based solar cells is about 29.4%, but with the use of tandem design, it is expected to achieve laboratory and mass production efficiencies of more than 30% or more.

4. Challenges faced by tandem solar cell

The design challenge for tandem solar cell is to find two semiconductor crystals with a well-matched lattice to match the corresponding bandgap width. Ideally, the top layer of the cell's conduction band should have about the same energy as the bottom valence band.

And electrons from the top semiconductor can easily enter the hole (valence band) of the bottom semiconductor lattice when excited by sunlight. Electrons are excited by different wavelengths of sunlight in the valence band, and the total power of the two parts of the battery is equal when working together.

However, if the valence and conduction bands are not properly matched at the junction, power losses will occur due to the resulting resistance when electrons flow through.

Compared to ordinary single-junction solar cells, tandem solar cell can absorb a wider range of solar spectrum, breaking the limitations of traditional solar cells due to time and other factors.

Challenges faced by tandem solar cell


It is believed that in the future, with the addition of advanced and novel technologies, the working efficiency of tandem solar cell will be greatly improved, and the cost and construction will be difficult.

5. Progress in BC and tandem technology of photovoltaic cells

As a general trend, tandem technology is widely regarded as an effective way to achieve more than the theoretical efficiency limit of existing silicon-based single-junction cells.

Research is also underway on the use of different types of backside contact technologies (e.g., IBC, TOPCon, etc.) to construct tandem cells. The future prospects of BC technology stacks for 12v 100ah lithium ion batteries are widely optimistic for the following reasons:

  • Potential for efficiency gains

Tandem technology can push the efficiency limits of single-junction silicon cells by combining different bandgap materials to capture different parts of the solar spectrum. Combined with backside contact (BC) technology, it can further reduce surface and interface recombination loss and improve photoelectric conversion efficiency.

  • Technological innovation drives cost reduction

With advances in manufacturing processes and large-scale production, the cost of BC tandem cells is expected to decrease. Material selection, equipment improvements, and production process optimization will help reduce costs and improve the price/performance ratio, making this high-efficiency battery more competitive in the market.

Progress in BC and tandem technology of photovoltaic cells

  • Policy support and market demand

Support policies have been continuously strengthened, which provides a good environment for the research and development and application of high-efficiency photovoltaic cell technology. BC tandem cells will play an important role in the energy transition due to their high efficiency.

  • Coordinated development of the industrial chain

With the technological progress and collaborative innovation of upstream raw materials, production equipment suppliers and downstream power station integrators, the industrialization process of BC tandem cell technology will be further accelerated.

  • Sustainability

Considering the infinite nature of solar energy resources and environmental protection attributes, the research and development of photovoltaic cells with higher efficiency is an important way to achieve sustainable energy utilization. BC tandem batteries will occupy a favorable position in the future competition in the clean energy market due to their excellent performance.

6. Conclusion

Photovoltaic tandem cell technology has a promising future, which not only brings new drivers to the solar industry, but also has the potential to change the global energy landscape.

With the deepening of research and the maturity of technology, tandem solar cells are expected to be widely used in commercial and residential markets in the future, making an important contribution to the realization of a sustainable energy future.


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