Mono-PERC (Passivated Emitter and Rear Contact) cells are a type of monocrystalline solar cells that have an additional passivation layer on the back side of the cell, which improves their efficiency and performance compared to traditional monocrystalline cells. The passivation layer helps to reduce recombination losses, allowing for more electrons to be collected and converted into electricity. Mono-PERC cells are more efficient, durable, and have a higher temperature coefficient, making them a popular choice for high-performance solar panels.