Power output performance analysis of back-contact photovoltaic module under actual field shading conditions: A comparison with TOPCon photovoltaic module

Back-contact (BC) solar cells exhibit low reverse bias characteristics due to their interdigitated PN junction design on the rear surface. Current literature and market perception suggest that BC modules have a power output advantage over front-contact modules (such as TOPCon) under partial shading, as the rear PN junctions of BC cells can undergo soft breakdown conduction. However, our study systematically investigates the applicability of this conclusion and finds that the output performance advantage of BC modules in shading scenarios is limited to specific conditions. Through comparative experiments simulating actual field shading conditions (single-cell shading, short-side row shading, and long-side row shading), we found that BC modules outperform TOPCon modules only when fewer than three cells in a substring are shaded. This is theoretically supported by the relationship between the breakdown voltage of BC cells (−5V) and the negative bias condition required for bypass diode activation in a substring (−15 V). In the case of short-side and long-side row shading commonly seen in large ground-mounted power stations, the output performance of the two tends to be consistent. This study establishes boundary conditions for the power output characteristics of BC modules under actual shading conditions, providing key references for engineering design and market investment.