We use cookies to improve your experience and for marketing. Read our cookie policy Manage cookies
Search across reports, market insights, and blog stories.
Scientists at Nanchang Hangkong University in China have devised a dual silicon oxide diffusion barrier approach to boost the performance of tunnel oxide passivated contact (TOPCon) solar cells. The method pairs post-plasma oxidation with tunnel oxide optimization to govern the depth profile of electrically active phosphorus and the microstructure of polysilicon (poly-Si).
Wenhao Chen, the corresponding author, told pv magazine that standard industrial TOPCon optimization has mostly concentrated on tuning the total phosphorus dose or tunnel oxide quality, without separately governing where the electrically active phosphorus peak resides within the polysilicon. He noted that phosphorus piling up at the surface boosts parasitic optical absorption without further lowering contact resistance, generating a trade-off between contact and optical losses in mass-produced cells.
Chen said the work shows an industry-compatible dual-SiOx diffusion barrier method built on post-plasma oxidation. Instead of physically redistributing phosphorus atoms, oxygen diffusing inward causes depth-selective dopant deactivation by forming electrically inactive P-O complexes. Lengthening post-plasma oxidation to 100 seconds moves the activated phosphorus peak from the poly-Si surface to a depth of roughly 50 nm, which closely matches the silver paste burn-off depth during screen-printing and co-firing.
Chen added that combining this with a densified bottom tunnel oxide barrier lets the dual-oxide confinement preserve high dopant activation and strong passivation quality. Industrial batch trials covering nearly 1,000 TOPCon cells sized 210 x 182.3 mm2 delivered an absolute efficiency gain of 0.07 percentage points. The gain stems mainly from lower contact resistivity and suppressed parasitic absorption, with only slight open-circuit voltage degradation. This straightforward process adjustment can be adopted on existing PECVD production lines to further raise the efficiency of commercial TOPCon solar cells, according to Chen.
The team produced TOPCon solar cells on n-type monocrystalline silicon wafers with resistivities from 1 to 3 ohm-centimeters. The cells received conventional alkaline texturing, boron diffusion, rear-side TOPCon fabrication, passivation, screen printing, high-temperature co-firing and laser-enhanced contact optimization. A bilayer phosphorus-doped polysilicon structure with silicon oxide diffusion barriers was deposited via plasma-enhanced chemical vapor deposition (PECVD) at about 435 C.
Five post-plasma oxidation durations were examined: 0, 66, 85, 100 and 120 seconds, where 66 seconds corresponds to the conventional industrial process and 100 seconds to the optimized condition. All samples were subsequently annealed at 910 C to crystallize the silicon layers and form the passivating contacts. The finished polysilicon layer measured approximately 100 nm in total thickness.
Photoconductance measurements were used to evaluate passivation quality, and the transmission line method determined rear contact resistivity. Secondary ion mass spectrometry and electrochemical capacitance-voltage profiling probed elemental distributions and electrically active phosphorus concentrations. X-ray diffraction, Raman spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy supplied further detail on crystallinity, surface morphology and chemical bonding. Completed cells were electrically tested to assess how the various oxidation treatments performed.
Analysis revealed that extending oxidation from the conventional 66 seconds to 100 seconds moved the electrically active phosphorus peak from about 20 nm to 50 nm beneath the polysilicon surface. Pushing oxidation to 120 seconds produced excessive phosphorus deactivation and worsened passivation quality. By optimizing the bottom tunnel oxide barrier, the team held the phosphorus peak near 50 nm while enhancing dopant activation and attaining an implied open-circuit voltage of 742.4 mV.
Material characterization pointed to inward-diffusing oxygen deactivating phosphorus by forming electrically inactive phosphorus-oxygen complexes rather than physically redistributing phosphorus atoms. The longer oxidation also enhanced near-surface crystallinity and modestly raised surface roughness, while overall polysilicon crystallinity stayed largely the same. Contact resistivity dropped from 1.54 to 1.00 milliohm-square-centimeters, though the researchers could not credit the gain solely to the phosphorus peak shift.
Industrial testing on 966 TOPCon cells showed average conversion efficiency climbing from 27.15% to 27.22%, a 0.07 percentage point improvement. A higher fill factor and greater short-circuit current drove most of the gain, while open-circuit voltage dipped slightly. Quantum efficiency measurements indicated lower parasitic absorption in the rear polysilicon contact, aiding the long-wavelength response.
The researchers concluded that the optimized oxidation process is a promising path to better industrial TOPCon cell performance, although separating the individual contributions of dopant deactivation, structural changes and optical effects remains difficult. The research team included scientists from Chinese PV manufacturer ZQi Solar Technology.
Interactive table based on the Store Companies dataset for this report.
Report Scope and Analytical Framing
Concise View of Market Direction
Market Size, Growth and Scenario Framing
Commercial and Technical Scope
How the Market Splits Into Decision-Relevant Buckets
Where Demand Comes From and How It Behaves
Supply Footprint and Value Capture
Trade Flows and External Dependence
Price Formation and Revenue Logic
Who Wins and Why
How the Domestic Market Works
Commercial Entry and Scaling Priorities
Where the Best Expansion Logic Sits
Leading Players and Strategic Archetypes
How the Report Was Built
World's largest monocrystalline silicon producer
Major PV manufacturer, high-efficiency cells
One of world's largest solar module producers
Leading PV module and cell manufacturer
Major LED chip and compound semiconductor producer
Global HQ in Canada, major ops in China
Major PV product manufacturer
Solar cell and module division
HJT solar cell specialist
Solar cell manufacturer
Major polysilicon and solar cell producer
Solar cell and module manufacturer
Solar cell and module producer
LED packaging and components
LED chip manufacturer
LED packaging and lighting solutions
LED packaging and components
Solar cell and module manufacturer
Solar cell producer
Crystal growth equipment and materials
Integrated circuits and LED chips
LED packaging and lighting
LED packaging and components
LED packaging and smart lighting
LED packaging and display products
LED chip technology company
LED packaging
PV manufacturing equipment
LED driver ICs and chips
LED packaging and components
Tell us where to send the sample and whether you want this report customized.
Thank you. Our team will review your request and reply to your business email.
Our team will review your request and route it to support@indexbox.io.
IndexBox, Inc.
2093 Philadelphia Pike #1441
Claymont, DE 19703, USA
Contact us
© 2026 IndexBox, Inc
Instant access. No credit card needed.
Online access to 2M+ reports, dashboards, and tables. Trusted by Fortune 500 teams.
Free Data: Solar Cells and Light-Emitting Diodes — China
Instant access. No credit card needed.

source