Indoor Characterization and Analysis of Reverse Breakdown Behavior of Solar Cells with Different Cell Architectures

With TOPCon cell technology becoming mainstream in 2025 and HJT/BC increasing their market share, too, cell strings now operate at higher voltages and current densities and exhibit different reverse-bias behavior than legacy PERC/Al-BSF. We experimentally compare reverse characteristics of five c-Si cell architectures (Al-BSF, PERC, TOPCon, HJT, IBC) using mini-modules and mini-strings measured from 100 to 1.300 W/m² at 25°C with a four-quadrant long-pulse flasher. TOPCon and HJT show pronounced hysteresis in the 1st quadrant but no relevant hysteresis in reverse; bifacial front and rear behavior is essentially identical. The key findings are that typical reverse breakdown voltage for Al-BSF is around -14 V, PERC between -21 and -24 V, HJT around -30 V, TOPCon between -44 and -49 V and for BC between -4 and -5 V. Illumination-dependent reverse current is strong for PERC, low for Al-BSF, very low for HJT and IBC, and overall low for TOPCon, considering more relevant voltages very low. Under full shading scenarios TOPCon and HJT strings with ≥24 cells per bypass diode are generally feasible as string voltages remain below reverse breakdown voltage onset. However, under partial shading (~50% coverage), PERC is most critical due to illumination-enhanced reverse current, while TOPCon/HJT dissipate less power. IBC breaks down early and therefore dissipates less power due to low breakdown voltage. Implications for hot-spot risk, bypass design, and applications with recurring shading (C&I, BaPV, BiPV) are discussed.