Solar cells are the core element of photovoltaic panels: they’re where electricity is generated by the photovoltaic effect. PERC (Passivated Emitter and Rear Cell) technology is an innovation in the manufacture of crystalline silicon photovoltaic cells (monocrystalline and polycrystalline) that improves their energy efficiency. It limits charge carrier recombination and improves light capture in the cell.
The problem: charge carrier recombination
In a solar cell, when incident light strikes the semiconductor material, it generates electron-hole pairs, where an electron is freed from its atomic bond and leaves behind a hole, which is the absence of an electron. These free electrons and holes are the charge carriers. To generate electric current, these charge carriers must be separated and directed towards the electrical contacts at the front and rear of the solar cell.
However, if an electron and a hole meet and come together before reaching the electrical contacts, they recombine, cancelling out their electrical charge. This process is called recombination, and it reduces the amount of current generated by the solar cell, thus reducing its energy efficiency.
The recombination of charge carriers should therefore be limited, in order to maximize charge separation and current generation, and thus improve the overall efficiency of the solar cell.
The solution: PERC technology
PERC technology involves adding a passivating dielectric layer to the back of the solar cell. Typically made of silicon oxide or aluminum oxide, this layer acts as a barrier for electrons and holes, reducing the recombination of charge carriers. In addition, the
- the passivating dielectric layer on the back of the cell reflects light back into the cell, enabling better light absorption and increased current generation.
- metal contacts are located at the rear of the cell, creating openings in the passivating dielectric layer. This reduces the amount of metal in contact with the rear surface of the cell and cuts recombination losses.
As a result, PERC cells have a higher open circuit voltage (Voc) than conventional solar cells, resulting in better overall solar cell performance.
Compatibility with half-cells
The question is: is PERC technology compatible with half-cells? The answer is yes: solar panel manufacturers often combine these two technologies to further improve panel efficiency and performance.
The compatibility of PERC and half-cell technology lies in the fact that each addresses different aspects of solar cell performance, without interfering with the other: while PERC technology adds a layer to the back of the cell, half-cell technology divides the solar cells in two. They are simply combined: first the dielectric layer is added, then the cell is cut in two.
The result is a solar panel that draws on the advantages of PERC technology to increase energy efficiency, and of half-cells to reduce electrical resistance and improve performance in partial shading. These two technologies complement each other, enabling the production of solar panels with optimized overall efficiency and performance.
Is it possible to have bifacial PERC panels?
Yes: in a bifacial PERC solar panel, PERC solar cells are used to improve energy efficiency, while the bifacial design enables sunlight to be captured on both sides of the panel.
Bifacial technology takes advantage of light reflected from the surface beneath the solar panel, enabling electricity to be generated from the back of the cell in addition to the front. By combining the benefits of the improved efficiency of PERC cells with the additional power-generating capacity offered by the bifacial design, PERC bifacial solar panels can offer superior overall performance to traditional single-sided monocrystalline or polycrystalline solar panels.
This makes PERC bifacial solar panels particularly suitable for large-scale solar installations, such as solar power plants or large commercial facilities, where maximizing energy production and optimizing space utilization are crucial.