UV-Induced Degradation of Industrial PERC, TOPCon, and HJT Solar Cells: The Next Big Reliability Challenge?

Abstract

With the surge of UV-transparent module encapsulants in the photovoltaic industry aiming to boost quantum efficiency, modern silicon solar cells must now inherently withstand UV exposure. UV-induced degradation (UVID) of nonencapsulated laboratory and industrial solar cells from several manufacturers is investigated. Passivated emitter rear contact (PERC), tunnel oxide passivating contact (TOPCon), and silicon heterojunction (HJT) cells can suffer from severe implied voltage degradation (>20 mV) after UV exposure relating to 3.8 years of module installation in the Negev desert. Front UV-exposure causes more performance loss than an equal rear dose. This is connected to a higher UV transmission of the cell layers outside the bulk, indicating the photons need to reach the silicon surface to induce damage. Current–voltage measurements of the TOPCon groups most sensitive to UV degradation show more than 7%_rel efficiency loss with the V_oc as the main contributor. For two TOPCon groups, dark storage for 14 days after UV exposure causes an additional voltage drop on a similar scale as the UV damage itself, impeding straightforward reliability testing. UVID appears to be a complex process general to all dominant cell architectures with the potential to diminish efforts in efficiency optimization within only a few years of field employment.