What is a PERC CELL?
PERC stands for Passivated Emitter and Rear Contact. Solar panels made from PERC solar cells typically perform better than traditional panels in both low-light conditions and high temperatures.
The construction of a PERC solar cell is not different from a typical photovoltaic solar cell. Both use silicon wafers to generate a flow of electrons using incoming solar radiation, and the overall construction of the cell types is very similar.
In a conventional solar cell, there is an aluminum back contact which makes contact across the full area of the back of the cell. PERC technology contains an extra dielectric passivation layer. The aluminum back contact is then applied on top of the dielectric layer.
As PERC is compatible with existing screen printing equipment, it's relatively easy for manufacturers to upgrade their current production lines to manufacture PERC solar cells, making this a more cost-effective solution in improving panel efficiencies.
PERC technology increases the overall panel performance by increasing a cell's ability to capture light.
1. PERC technology increases the cell efficiency through the dielectric passivation layer that reflects the cell's light that has passed through to the rear without generating electrons. Through this reflection, the photons have another opportunity to generate current.
2. PERC technology can capture light at longer wavelengths. In early mornings and evenings or under overcast conditions, a higher quantity of blue light is generally converted to energy near the top of the cell. In contrast, red light with higher wavelengths penetrates further through the cell and is converted to energy near the bottom. The 'reflective' properties of the PERC technology ensure increased absorption of red light, even in weak or diffuse light conditions, delivering better energy yields.
3. In standard cells, wavelengths above 1180 nm are not absorbed by the silicon wafer. Instead, such wavelengths are merely absorbed into the aluminum back contact, generating heat, which increases the temperature of the cell and reduces its conversion efficiency. As the PERC layer reflects this light through the cell and out of the panel, it reduces the amount of absorption by the back contact, and therefore, the heat builds up in the cell. This reduction in absorption helps the cell to work at a cooler temperature, improving the energy yield.
4. Electrons tend to recombine in the solar cell, which causes a blockage in the free movement of electrons through the solar cell. This inhibition of free electron movement reduces the cell efficiencies. The addition of a dielectric passivation layer in PERC technology reduces this, improving the energy yield.