TOPCon crystal growth increasingly targets low oxygen and carbon concentrations to support higher cell efficiencies and process stability
Wafer thickness remains around 130 µm, with the industry continuing to pursue thinner wafers to reduce silicon consumption
Rectangular wafer formats, particularly 182 × 210 mm and 210 × 210 mm, are emerging as the mainstream formats for TOPCon manufacturing
With TOPCon now established as the dominant solar cell technology, manufacturers are increasingly focusing their optimization efforts on wafer-level parameters, including oxygen concentration, thickness, and wafer format. These refinements are intended to support efficiencies beyond 25% while enabling the transition to larger, higher-power module formats (see TOPCon Remains Mainstream As Optimization Pathways Continue).
Electrical Parameters
For TOPCon, a resistivity between 1 and 3 Ω.cm is characterized as the sweet spot for TOPCon, striking a careful balance between series resistance and carrier lifetime. The latter is a crucial factor in itself: for TOPCon to reach an efficiency beyond 25%, bulk lifetimes must exceed 1,000 µs (1 ms). Leading manufacturers now regularly target 1.5-2.5 ms for their premium lines. Oxygen content is also tightly controlled, typically kept below 10-12 ppm. Carbon levels are closely monitored as well, typically kept below 1 ppm, since too much carbon can trigger unwanted defect complexes during high-temperature processing.
Physical Parameters
The spec for wafer thickness for TOPCon also lies between that of its competing technologies. The mainstream specification has remained largely unchanged, with around 130 µm still the industry standard. This is not expected to shift significantly in the near term either, with projections from the China Photovoltaic Industry Association (CPIA) indicating only limited scope for further thinning in wafers for TOPCon over the coming years (see ITRPV Outlines Key PV Technology & Market Trends).
As to the dimensions, the segment is more stable now. According to the CPIA, the silicon wafer market in 2025 was the most diversified in terms of available sizes, being flooded with different sizes, including 166 mm and below, 182 mm square, pseudo-square, rectangular, and 210 mm square wafers, each with a considerable market share. There is a clear shift toward larger formats now. Wafers measuring 166 mm or less now account for a minuscule share of the market and are expected to be phased out this year. Likewise, 182 mm square and pseudo-square wafers, which held respective shares of 11.2% and 21.4%, are also set to decline and are expected to exit the market between 2026 and 2028.
In contrast, larger formats are gaining ground. The 210 mm square now holds an 18.9% share, while rectangular wafers have emerged as the dominant format, accounting for 48.2%. Among these, rectangular wafers are increasingly seen as the future mainstream, driven by improved utilization of module area and higher power output potential. That said, even within the rectangular format, the situation is far from uniform. Each leading manufacturer tends to favor its own wafer dimensions, often tailoring sizes to specific product strategies and applications. As highlighted in our previous report, the market is characterized by a wide variety of formats, with some companies offering modules based on up to 4 different wafer sizes.
From a TOPCon perspective, 182 × 210 mm and 210 × 210 mm are the mainstream wafer formats, looking at the top products from leading manufacturers. A few companies are also using special sizes, such as 182.3 × 210 mm and 182.2 × 182.2 mm, while Jetion is using a larger variant of G12, the 210.3 × 210.3 mm wafer.
The text is an edited excerpt from TaiyangNews’ latest report on Cell & Module Technologies Trends 2026, which can be downloaded for free here.