PERCPassivated Emitter and Rear Cell

In a PERC cell, a dielectric layer (usually Al2O3 + SiNx) is deposited on the back of the P-Type cell. This layer reflects unabsorbed photons back to the cell (second chance absorption) and passivizes back surface defects. The improvement in efficiency compared to standard BSF cell is +0.5 to +1.0 absolute point. PERC suffers from an intrinsic defect: LID (Light Induced Degradation) degradation which is more marked in P-Type, and LeTID degradation under certain thermal conditions. The TOPCon N-Type solves both of these problems.

In Switzerland in 2026, PERC is at the end of its commercial life. Most installers offer TOPCon N-Type for any new installation. If an installer still offers you PERC, it is either old-gen stock at a knockdown price (acceptable if the savings are real), or a lack of technological update (alarm). The LID degradation of PERC can represent 1-3% loss in the first year — to be negotiated in your guarantee.