A research team from the University of New South Wales (UNSW) and Chinese PV manufacturer DAS Solar have investigated how laser cutting affects the performance of back-contact TOPCON (TBC) silicon solar cells, in an effort to identify the dominant cut-induced loss mechanisms and determine practical design conditions that minimize efficiency degradation in cut-cell and module applications.
“Our work establishes practical design guidelines for industrial TBC cut-cell manufacturing and demonstrate that optimized gap-region cutting can substantially mitigate cut-induced recombination losses without additional edge-passivation processing,” UNSW Professor Martin Green told pv magazine. “It was done in conjunction with DAS Solar, reportedly the first to bring GW-scale TOPCon manufacturing into production with the work supported by DAS Solar and the Australian Renewable Energy Agency (ARENA).
The scientists explained that cutting full-size solar cells into half, third, or quarter segments minimizes resistive losses, which scale quadratically with cell length. While this practice is now standard in crystalline-silicon module manufacturing, laser scribing exposes raw, unpassivated edges and creates dangling bonds and process defects that significantly elevate carrier recombination and affect cell performance.
Through Quokka3 device simulations, the researchers evaluated half-, third-, and quarter-cell configurations, including realistic deviations in the laser-cut position within the designed gap regions. Quokka3 is a numerical solar-cell simulation software that models the electrical behavior of photovoltaic devices, including carrier generation and recombination, current transport, and distributed resistive losses.
“Our analysis showed that the efficiency loss caused by cut-induced edge recombination increases linearly with the ratio of cut-edge length to active cell area,” Green stated. “We also found that cutting in the gap between n-type and p-type contacts reduces the efficiency penalty by approximately 50% compared with cutting through the p-type contact region.”
Among the evaluated cut locations, gap-region cutting yields the lowest efficiency loss, because the cut edge is spatially separated from the heavily doped emitter and back-surface-field (BSF) regions. This separation limits the interaction between the newly exposed, unpassivated silicon surface and the carrier-selective junctions, thereby reducing edge-induced carrier recombination.
In contrast, emitter-region cutting causes the most pronounced efficiency degradation, as the laser-cut edge directly exposes the emitter space-charge region. This exposed junction is highly susceptible to recombination, allowing photogenerated electrons and holes to recombine at the cut edge and thereby reducing the effective carrier population available for collection.
Overall, the results demonstrate that placing the cut within the gap between the emitter and BSF regions provides the most effective strategy for suppressing edge-recombination losses and preserving TBC cell efficiency.
“The simulations also showed that cut cells exhibit larger efficiency losses under low irradiance due to increased resistive losses and recombination of diffusive hole transport, with an optimal post-cut gap width of approximately 0.3 mm being identified for minimizing the total efficiency loss,” Green emphasized.
As the light intensity decreases, TBC cut cells become more susceptible to edge-related recombination, as photogenerated carriers are more likely to diffuse laterally toward the recombination-active cut edges before being collected. At the same time, reduced carrier concentrations increase the relative impact of resistive losses, resulting in a higher effective series resistance associated with lateral hole transport. Consequently, the efficiency penalty caused by cell cutting becomes substantially more severe under low-light operating conditions.
The research work was presented in “Simulation of gap-region cutting for suppressing edge recombination losses in tunnel oxide passivated back-contact solar cells,” published in Solar Energy.
UNSW and DAS Solar previously collaborated on the fabrication of a TBC cell with a power conversion efficiency of 27%. The cell is based on a zero-busbar (ZBB) design, which the scientists said required significantly lower silver (Ag) content for metallization.
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