Laser‑Patterned Contacts Boost TOPCon to 26%

New laser‑patterned poly‑Si fingers cut losses and lift efficiency to 26.08%

The breakthrough rear‑side patterning method developed by Yangzhou University researchers reduces parasitic absorption in the poly‑Si layer and pushes certified cell efficiency to 26.08% % – one of the highest reported for an industrial n‑type TOPCon cell. By using a picosecond green laser to selectively remove poly‑Si from non‑metalized regions and then a precision KOH wet‑etch, the team creates narrow “poly‑fingers” that keep electrical contact where needed while exposing the rear surface to light.

How the laser‑assisted poly‑finger process works

The process starts with a standard TOPCon wafer that already carries a SiOₓ/poly‑Si stack. A picosecond laser scans the rear surface, locally heating and modifying the poly‑Si so that it can be lifted away in the subsequent KOH bath. The wet‑etch creates clean gaps between the metal contacts, eliminating near‑infrared absorption that would otherwise turn photons into heat. Crucially, the laser energy density is tuned so that the poly‑Si under the metal fingers remains intact, preserving carrier‑collection pathways.

Certified 26.08% efficiency – why it matters

The champion cell measured an open‑circuit voltage of 746.1 mV, a short‑circuit current density of 14.014 A cm⁻¹ and a fill factor of 83.6 %, delivering a power conversion efficiency of 26.08% that was independently certified by Germany’s ISFH laboratory. This result shows that rear‑side optical loss can be cut without sacrificing the excellent passivation that makes TOPCon cells so efficient.

TOPCon market racing ahead – the global backdrop

The TOPCon segment is exploding: forecasts put the global market at USD 13.66 bn in 2026 and USD 29.83 bn by 2033 (Coherent Market Insights), while another analyst predicts a 23.9 % CAGR to USD 159.45 bn by 2034 (Zion Market Research). These numbers confirm that every efficiency gain, such as the 26 % cell, adds significant value for manufacturers and investors.

Balancing optical gain and electrical transport

Laser‑induced poly‑Si removal improves light transmission, but too deep a modification can damage surface passivation and raise series resistance. The researchers identified an optimal KOH etch time of 480 s and a laser overlap setting that yields uniform gaps while keeping electrical performance high. Simulations with TCAD and Quokka 3 illustrate the trade‑off between wider gaps (which increase optical gain) and the need to maintain lateral carrier transport.

What it means for Israel’s rooftop solar market

Israel’s typical residential system yields about 1,700 kWh kWp⁻¹ yr⁻¹ in the central region. A 15 kW home system using a conventional 20 % module would therefore generate roughly 25,500 kWh yr⁻¹. Replacing those modules with the new 26.08 % TOPCon cells raises the effective efficiency by a factor of 26.08 % / 20 % ≈ 1.30, lifting the annual yield to ≈ 33,150 kWh (1,700 × 1.30 × 15). At the residential feed‑in tariff of ₪0.48 /kWh, that extra 7,650 kWh translates into ≈ ₪3,700 more revenue per year. With a typical turnkey cost of ₪3,150 /kWp, a 15 kW system costs ≈ ₪47,250; the higher output shortens the simple payback from about 4 years to roughly 3 years, improving the investment case for Israeli homeowners.

Outlook – scaling the laser‑patterned rear for mass production

The authors stress that the method uses existing industrial laser tools and standard KOH baths, making it compatible with current TOPCon production lines. If manufacturers adopt the technique, we can expect commercial modules that consistently exceed 26 % efficiency, narrowing the gap to the theoretical silicon limit (~29 %). Combined with the rapid growth of the TOPCon market, this could accelerate the shift away from traditional Al‑back‑contact cells and help Israel meet its 30 % renewable electricity target for 2030.

What it means for Israel (summary)

Higher‑efficiency TOPCon modules mean more kilowatt‑hours from the same roof area, faster payback for residential solar, and a stronger contribution toward national clean‑energy goals. Homeowners can expect roughly 30 % more energy and about ₪3.5 k extra annual income per 15 kW system, while installers gain a premium product that aligns with global market momentum.

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Sources & further reading

• Which region will lead the global TOPCon solar cell market in 2026?
• TOPCon Solar Cells Market Size, Share, Growth Report, 2034
• Topcon Solar Cell Market Size, Growth, Research Reports, 2033
• TOPCon Solar Cells Market By Size, Share and Forecast 2028 | TechSci Research
• TOPCon Solar Cell Market Size ($39.2 Billion) 2030