Revolutionizing Solar Power: China's 26.66% TOPCon Efficiency Milestone

In a groundbreaking advancement for renewable energy, Chinese researchers have achieved a certified power conversion efficiency (PCE) of 26.66% in industrial-scale Tunnel Oxide Passivated Contact (TOPCon) solar cells. This record, announced alongside a publication in Nature Energy, marks a significant leap for mass-producible photovoltaic technology, bringing real-world performance closer to theoretical limits. Developed through collaboration between the Ningbo Institute of Materials Technology and Engineering (NIMTE) under the Chinese Academy of Sciences (CAS), Zhejiang JinkoSolar Co., Ltd., Soochow University, and China Jiliang University, the innovation promises to accelerate global solar adoption by enhancing efficiency without exorbitant costs.

This achievement on M10-size wafers (182.75 mm × 182.75 mm, effective area 313.3 cm²) demonstrates viability for large-scale manufacturing lines, positioning TOPCon as a frontrunner in the transition from older PERC cells to next-generation n-type architectures.

Demystifying TOPCon Solar Cells: From Concept to Core Technology

Tunnel Oxide Passivated Contact (TOPCon) solar cells represent an evolution in crystalline silicon photovoltaics. Unlike traditional PERC (Passivated Emitter and Rear Cell) designs, which rely on a dielectric rear passivation layer, TOPCon introduces an ultra-thin tunnel oxide layer (about 1.5 nm thick) topped with a heavily doped polycrystalline silicon (polySi) layer on the rear side. This carrier-selective contact allows electrons to tunnel through while blocking holes, drastically reducing recombination losses and boosting voltage output.

The process begins with n-type silicon wafers, preferred for their lower light-induced degradation (LID) and light-and-elevated temperature degradation (LeTID) compared to p-type in PERC. Key fabrication steps include: depositing the tunnel oxide via thermal oxidation, LPCVD (low-pressure chemical vapor deposition) for polySi, doping, annealing for crystallization, and metallization. This high-temperature compatibility with existing PERC lines makes TOPCon a drop-in upgrade for factories worldwide.

Advantages over PERC include higher open-circuit voltage (Voc up to 745 mV here), superior bifaciality (88.3% in this record), and potential efficiencies nearing 28.7% theoretically. Versus Heterojunction (HJT), TOPCon offers lower capital expenditure—no need for amorphous silicon deposition tools—and better humidity tolerance during production.

The Dual-Side Electrical Refinement: Engineering the Record

The heart of this TOPCon solar cells efficiency record lies in a novel dual-sided synergistic strategy. On the front side, researchers paired a high-sheet-resistance boron emitter (~430 Ω/sq) with an optimized metallization grid. This minimizes shading losses and Auger recombination while maximizing passivation quality, a step-by-step balancing act refined through simulations and PL/EL imaging.

• High-resistance emitter reduces surface recombination velocity.
• Optimized fingers and busbars cut series resistance by 5-10%.
• Result: Fill factor (FF) of 85.57%.

Rear-side innovation features a double-layer tunnel oxide/polySi stack: an inner highly crystalline polySi for passivation and an outer barrier layer blocking silver (Ag) diffusion from screen-printed electrodes. Secondary ion mass spectrometry (SIMS) confirmed no Ag penetration into the substrate, averting degradation. Localized thinning of the rear polySi further enhanced light transmission for bifacial gains.

"The device has reached 83.8% of the theoretical efficiency limit, outperforming conventional TOPCon solar cells," noted Prof. Jichun Ye, corresponding author from NIMTE.

Performance Benchmarks and Independent Certification

The cell's metrics shine: short-circuit current density (Jsc) optimized via EQE analysis, Voc of 744.6 mV, and overall PCE certified at 26.66%—a world record for industrial TOPCon on full-area M10 wafers. This eclipses prior industrial marks (e.g., 26.09% from NIMTE in Dec 2025) and approaches lab-scale records like JinkoSolar's own 27.02%.

Bifaciality at 88.3% means superior rear-side generation, ideal for ground-mounted systems. TEM and Raman confirmed microstructural excellence: high polySi crystallinity (>90%) and minimal inactive phosphorus.

Higher Education's Pivotal Role: Universities Driving the Breakthrough

This Chinese TOPCon breakthrough underscores academia's synergy with industry. Soochow University's optoelectronics experts contributed emitter design, while China Jiliang University's materials chemists optimized passivation layers. NIMTE, CAS's flagship, bridged lab-to-fab, with JinkoSolar scaling prototypes.

Such collaborations exemplify China's higher education ecosystem fueling PV dominance. Programs in materials science, photonics, and renewable energy at these institutions produce PhD talent for R&D roles. Aspiring researchers can explore research jobs in solar tech or career advice for academia.

China's universities rank high globally in PV citations, with Shanghai Jiao Tong and Tsinghua leading related fields.

China's Unrivaled Solar Manufacturing Supremacy

China commands over 80% of global solar PV capacity through 2026, producing 700+ GW modules annually. TOPCon lines dominate new investments, with shipments projected at 600 GW/year by 2027 (70-80% market share). JinkoSolar, Tongwei, and Trina lead, exporting 200+ GW modules.

• Polysilicon: 96% global share.
• Wafers/cells/modules: 85%+.
• Cost drop: TOPCon LCOE 20-30% below PERC.

This scale enables rapid iteration, turning lab records into gigawatt production.

TOPCon vs Competitors: A Comparative Edge

TOPCon bridges PERC affordability and HJT performance, ideal for terawatt-scale deployment.

Global Impacts: Accelerating the Energy Transition

This industrial TOPCon solar breakthrough slashes LCOE, enabling cheaper utility-scale projects. With bifacial gains, energy yield rises 10-20% in reflective setups. For developing nations, it democratizes clean power; China exports fuel 50%+ global additions.

Implications span supply chains: reduced silver use (key innovation), lower BOS costs. Environmentally, higher eff means fewer panels/land.

Overcoming Hurdles: Silver Diffusion and Passivation Challenges

Past TOPCon pitfalls—Ag migration degrading passivation, suboptimal emitters—are solved here. Future risks: scaling uniformity, polySi quality control. Solutions include AI-optimized deposition, advanced annealing.

Photo by ling ze on Unsplash

Looking Ahead: Beyond 26.66% to Tandem Futures

By 2028, Jinko targets 28% TOPCon; hybrids with perovskite loom at 30%+. Chinese academia leads, with research positions booming. Explore higher ed jobs in PV or China university opportunities.

This record heralds cheaper, greener grids worldwide.