Solar scientists have unveiled a new metallization strategy that has pushed tunnel oxide passivated contact (TOPCon) solar cells to a certified power conversion efficiency of 26.31%, placing the technology among the most efficient crystalline silicon platforms reported to date. The advance targets one of the most stubborn barriers in high-efficiency photovoltaics: how to create highly conductive metal contacts without damaging the delicate surfaces that enable a solar cell to capture and preserve charge.
The strategy was developed by a research team led by Prof. Ye Jichun at the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences, in collaboration with Soochow University, Zhejiang Gonda Electronic Technology Co., Ltd., and JA Solar Technology Co., Ltd. Their findings, published in Matter, combine a specially engineered aluminum-free silver paste with a laser-based contact treatment known as laser-enhanced contact optimization, or LECO.
Crystalline silicon remains the dominant material in the global photovoltaic industry, but manufacturers are under intense pressure to extract more electricity from every wafer while lowering production costs. TOPCon cells have emerged as one of the leading candidates for this next stage of development because they can be integrated into manufacturing lines used for conventional silicon cells. Their structure places an ultrathin oxide layer and a doped silicon contact beneath the metal electrode, separating surface passivation from charge collection.
That separation is crucial. Solar-cell surfaces contain defects that can act as recombination centers, allowing electrons and holes generated by sunlight to annihilate before they can contribute to an electric current. The tunnel oxide and doped contact in TOPCon devices suppress this recombination while still allowing charge carriers to pass through. In principle, the architecture offers both excellent electronic passivation and low contact resistance. In practice, however, the process used to form metal electrodes can undermine both advantages.
Conventional TOPCon metallization often relies on silver-aluminum pastes that are fired at high temperatures. The heat helps the metal penetrate and establish an electrically conductive connection, but it can also degrade the passivation layer, disrupt the silicon lattice, and promote aluminum-induced alloying. These effects increase recombination and electrical losses. At the same time, screen-printed metal lines tend to become wider during processing, covering more of the light-facing surface and reducing the amount of sunlight that reaches the silicon absorber.
The researchers addressed the problem by redesigning the silver paste at the molecular level. Their aluminum-free formulation was engineered to have a carefully controlled molecular configuration and a strong intermolecular hydrogen-bonding network. These features give the paste high thixotropy, meaning it flows under the force of screen printing but rapidly regains its shape once the printing pressure is removed. The result is a narrow, sharply defined electrode that maintains its geometry during subsequent processing.
This shape retention enabled the team to produce front metal gridlines with an aspect ratio of 55%. A high aspect ratio allows a gridline to remain relatively tall while keeping its footprint narrow. That geometry reduces optical shading, allowing more photons to enter the cell, while preserving enough cross-sectional area for efficient lateral current transport. The aluminum-free composition also reduces the chemical aggressiveness of the paste, helping protect the passivation structure beneath the electrode.
The second part of the innovation is the LECO process. Instead of exposing the entire front contact to prolonged, high-temperature firing, a single-frequency laser scans the printed gridlines while the cell is held under reverse bias. The electrical bias drives carriers through the device, while the laser produces localized Joule heating in selected regions. Together, these effects generate the conditions needed to establish low-resistance electrical contacts at discrete points.
This localized reaction is fundamentally different from conventional firing. Rather than broadly disturbing the silicon and oxide layers across the entire electrode area, LECO confines contact formation to carefully controlled sites. The approach minimizes lattice disruption and avoids the extensive aluminum-related damage associated with traditional silver-aluminum metallization. The newly designed paste is essential because it can withstand the laser-assisted process while maintaining narrow, well-defined gridlines.
The combined effects improved both charge extraction and light collection. The resulting TOPCon cells achieved a certified efficiency of 26.31%, while their short-circuit current density reached 41.98 milliamperes per square centimeter. Short-circuit current density, commonly abbreviated as Jsc, measures the current generated per unit area when the cell operates at zero external voltage. The reported value is particularly significant because it reflects the enhanced spectral response and reduced optical shading of the devices, and was described by the researchers as the highest certified Jsc reported for large-area TOPCon solar cells at the time of publication.
The achievement suggests that the future of high-efficiency silicon photovoltaics may depend not only on new absorber materials or more complex cell architectures, but also on microscopic control of how metal contacts interact with semiconductor surfaces. By resolving the usual trade-off between low contact resistance and strong passivation, the synergistic metallization strategy offers a route that is compatible with industrial production. If scaled successfully, it could help manufacturers increase the output of TOPCon modules without requiring entirely new factory infrastructure, bringing more electricity from the same area of silicon and potentially accelerating the next wave of solar-power deployment.
Subject of Research:
A synergistic metallization strategy for improving the efficiency of tunnel oxide passivated contact (TOPCon) solar cells.
Article Title:
26.31%-Efficiency TOPCon Solar Cells Enabled by Synergistic Metallization with Reduced Optical Shading and Contact Resistance Losses
News Publication Date:
6-Aug-2026
Web References:
https://doi.org/10.1016/j.matt.2026.102965
References:
Matter, DOI: 10.1016/j.matt.2026.102965
Keywords
TOPCon solar cells, photovoltaic technology, solar-cell efficiency, metallization, aluminum-free silver paste, laser-enhanced contact optimization, LECO, crystalline silicon, passivation, contact resistance, optical shading, solar energy
