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DMEGC highlights TOPCon efficiency gains through low doping, ultra-dense metallization grids, optimized anti-reflection layers, and interface engineering
Hydrogen passivation, alumina layer optimization, and interface cleaning improved Voc, fill factor, and Isc, with several process steps contributing gains of around 0.1%-0.15%
Emerging TOPCon architectures, such as edge passivation and poly-finger designs, are creating new requirements for metallization paste chemistry, fire-through behavior, and thermal stability
As solar cell technologies approach their practical efficiency limits, manufacturers are increasingly relying on incremental process refinements to deliver further performance gains. Improvements across doping, passivation, optics, interface engineering, and metallization are collectively contributing to measurable efficiency enhancements.
DMEGC’s Solar Cell Technology Director, Roy Ren, also presented several improvements that have led to small incremental efficiency gains during his talk at the TaiyangNews High-Efficiency Solar Technologies Conference 2025. One such key refinement discussed was low doping, combined with an ultra-dense grid and narrower line width. By optimizing surface doping to achieve higher sheet resistance and improving current collection through dense metallization patterns, DMEGC reported an efficiency gain of about 0.1%, with increases in Voc and Isc. This approach balances recombination reduction with resistive loss management.
On the optical side, DMEGC optimizes the silicon anti-reflection layer, particularly multi-layer structures incorporating low-refractive-index films. The data presented indicate an efficiency gain of roughly 0.1%, largely driven by improved Isc. In addition to electrical performance, the multi-layer design enables a darker module aesthetic, which is in demand in specific markets.
The other topic of interest was passivation layer optimization, focused on tuning the thickness of the interfacial alumina layer and refining annealing conditions. The presentation shows improvements in Voc and fill factor, resulting in efficiency gains of over 0.1%. As n-type architectures push toward higher voltages, interface quality becomes increasingly critical.
Hydrogen passivation leverages hydrogen-rich SiNx layers. Under light activation, hydrogen diffuses to passivate defects at the silicon interface. The presentation reports efficiency gains of around 0.15%, primarily reflected in Voc and fill factor. Interface cleaning further improves surface quality through optimized chemical treatments, including NaOH and H₂O₂ adjustments, yielding additional efficiency gains and measurable improvements in Voc and Isc.
Metallization remains a critical process affecting both cost and performance. The pastes, especially, are also very sensitive to any process or structural changes. For example, both the key developments in TOPCon – edge passivation and poly-finger – while not directly related to metallization, also require optimization in paste formulations. As for poly-finger, the paste’s fire-through capability needs to be adjusted to reduce shunting, while maintaining Voc and FF. The difference with edge passivation is that the cells are subjected to a processing temperature of 300°C for 30 minutes to 2 hours, which influences the performance of front-side LECO pastes. These influences can be reduced by adjusting the paste frit chemistry.
The other hardcore metallization topics include stencil printing, laser transfer printing, and ‘silver-lean’ approaches, such as silver-coated copper and 2-layered metallization consisting of a seed layer and a top conductor layer, which is under evaluation.
The text is an edited excerpt from TaiyangNews’ report on Cell & Module Technology Trends 2026, which can be downloaded for free here.
