Solar panels create electricity through the flow of electrons from the n-type layer of the silicon semiconductor into the p-type layer. In the n-type layer free electrons are abundant, while in the p-type layer, there are more ‘holes’ where electrons could fit into. 

When sunlight strikes a solar panel it causes those free electrons in the n-type layer to become excited and pass through the contact point. This generates an electric current which either passes along the strong through the other solar panels, or out into the load. 

Afterwards, the electron comes back into the p-type layer to recombine with a corresponding hole layer.

However, this process does not work as intended. Sometimes electrons recombine with holes when they strike the silicon on the front or rear of the solar cell without ever passing through the contact point. 

This process is called surface recombination, and anytime it occurs there is a loss of electricity which could have been generated as the e-h pair.

Traditional solar panels which were designed with an Aluminium Back Surface Face (Al-BSF) were highly susceptible to rear surface recombination, as well as overheating from absorbing sunlight.

PERC solar cells are designed to reduce the level of surface recombination suffered in traditional solar panels through the use of a process called passivation.

The key to PERC solar cells is the addition of a surface passivation layer of silicon nitride (SiN) or Aluminium Oxide (AlO) layers to the surfaces of the solar cell, or possibly to both the front and rear. These layers reduce the amount of surface recombination and reflect light back into the solar cell.

The passivation layers act as insulation which reduces contact between the silicon of the solar cell and the metal back surface, where recombination occurs, except at the contacts.

PERC solar panels are available in both monocrystalline and polycrystalline designs, as there is little alteration to the manufacturing process.

The key elements of PERC Solar Cells are:

PERC solar cells offer a number of advantages in improving the efficiency and cost-effectiveness of solar panels compared with traditional panels, and can compete with newer technologies such as TOPCon or Heterojunction solar cells.

PERC solar cells were first developed at the University of South Wales over the course of the 1980s, but it would be many decades until they would see commercial use. 

For a long time complex manufacturing elements such as using photolithography to create contact windows in the rear dielectric layer, or limitations in the early use of silicon oxide (SiO) as a passivating chemical made it impractical for them to see commercial use.

Another issue which prevented the adoption of PERC technology into solar panels for many years was that it was more susceptible to Light Induced Degradation (LID) and Potential Induced Degradation (PID) than traditional solar panel designs. 

However, those various limitations have since been overcome by manufacturers, with PERC solar panels first coming on the market in the 2010s.

In 2017 PERC cells accounted for 20GW of new capacity, roughly 8% of the global new capacity, but this figure has only grown since and is expected to continue to do so.

Over the course of the 2020s, PERC technology is expected to become present in up to 50% of the global solar PV industry over the course of the decade, taking a dominant position in the market.

With a huge push towards solar energy in order to meet climate targets globally the scalability of manufacturing is a key concern. PERC solar panels offer efficiency levels close to what the very best solar cells can offer, with far easier manufacturing processes.