LECO process can increase resistance of TOPCon cells by ‘orders of magnitude’

Facebook
Twitter
LinkedIn
Reddit
Email
According to the report’s authors, LECO is now used in the production of around one-quarter of TOPCon cells. Image: Trina Solar.

A new study has found that the laser-enhanced contact optimisation (LECO) process used in the production of tunnel oxide passivated contact (TOPCon) solar cells could increase those cells’ resistances by “orders of magnitude”, potentially impacting their conversion efficiency over the long-term.

The research, conducted by scholars at the Department of Materials at the University of Oxford, tested the impacts of the LECO process, which involves applying a laser to the front side of the solar cell to promote greater diffusion between the cell’s silver and silicon materials. This can reduce the resistance of the cell, a measure of efficiency losses caused by the interaction of components made of different materials.

This article requires Premium SubscriptionBasic (FREE) Subscription

Unlock unlimited access for 12 whole months of distinctive global analysis

Photovoltaics International is now included.

  • Regular insight and analysis of the industry’s biggest developments
  • In-depth interviews with the industry’s leading figures
  • Unlimited digital access to the PV Tech Power journal catalogue
  • Unlimited digital access to the Photovoltaics International journal catalogue
  • Access to more than 1,000 technical papers
  • Discounts on Solar Media’s portfolio of events, in-person and virtual

Or continue reading this article for free

The researchers subjected the cells to temperatures of 400 degrees Celsius and to reverse bias testing – where a cell is subjected to a voltage to increase the electric field present at the P-N junction within a semiconductor – to test the impacts on cell resistance.

They found that the contact resistance of these cells, when subjected to the LECO process, increased from 4.8Ω (ohm) to 320Ω. This led to a relative efficiency loss of around 95% compared to the cell’s starting values, a significantly higher figure than the 0.6% efficiency gain delivered by using the LECO process that is cited in the report.

The growing position of TOPCon cells in the global solar sector means that processes such as LECO are an increasingly important part of the industry. Last year, Bram Hoex, deputy head of the School of Photovoltaic and Renewable Energy at the University of New South Wales, told PV Tech Premium that laser-assisted firing is “the biggest innovation in solar cell manufacturing in the last couple of years”.

Indeed, despite the preliminary conclusions of the report, its authors note that this does not necessarily mean that the LECO process is somehow fundamentally flawed, and further study is required. The researchers highlight that the combination of testing biases and temperature stresses simultaneously means it is unclear the extent to which each component affects the resistance gain and efficiency loss, and that “further investigations will be required to decouple these components”.

“This phenomenon highlights a broader reliability issue for solar cells in operation, as the increase in [resistance] can directly impact the device’s long-term stability and efficiency,” wrote the report’s authors.

Maximising solar generation in extreme weather

The potential impact of temperature on these resistance figures is significant, considering that solar modules will need to be deployed in an increasingly diverse and extreme range of environments if the world is to meet its decarbonisation targets.

A report from Dii Desert Energy, into the future of renewable power in the Middle East and North Africa (MENA) region, forecast the area to increase its cumulative installed solar PV capacity from 22.3GW at the end of 2024 to 75GW by 2030, with PV to account for more than half of the region’s total installed renewable energy capacity by the end of this decade.

Earlier this year, researchers from the DEWA R&D Center in Dubai wrote a piece on the role of new testing standards for solar systems deployed in desert environments, as developers look to build projects that operate effectively in desert conditions for decades.

Beyond just the extremities associated with desert environments, the impacts of climate change could usher in a new era of more extreme weather, posing challenges for PV asset managers. Earlier this year, Marcel Suri, CEO of Solargis, wrote a piece for PV Tech in which he argued that the deployment of solar projects in regions with more extreme weather would necessitate the use of higher-quality data, and a more sophisticated approach to data collection and usage, in order to maximise these projects.

7 October 2025
San Francisco Bay Area, USA
PV Tech has been running an annual PV CellTech Conference since 2016. PV CellTech USA, on 7-8 October 2025 is our third PV CellTech conference dedicated to the U.S. manufacturing sector. The events in 2023 and 2024 were a sell out success and 2025 will once again gather the key stakeholders from PV manufacturing, equipment/materials, policy-making and strategy, capital equipment investment and all interested downstream channels and third-party entities. The goal is simple: to map out PV manufacturing in the U.S. out to 2030 and beyond.
10 March 2026
Frankfurt, Germany
The conference will gather the key stakeholders from PV manufacturing, equipment/materials, policy-making and strategy, capital equipment investment and all interested downstream channels and third-party entities. The goal is simple: to map out PV manufacturing out to 2030 and beyond.

Read Next

June 2, 2025
A new manufacturing method has produced tandem perovskite-silicon tandem solar cells with a conversion efficiency of 27.8%.
May 29, 2025
Researchers have developed a new methodology they hope will improve the modelling of the impact of different types of dust on PV performance.
Sponsored
May 28, 2025
Ben Willis speaks to Astronergy about its next-generation TOPCon offering and the advantages of its zero-busbar module design, both of which were on show at Intersolar 2025.
Premium
May 27, 2025
Inverters are critical to PV systems but are often over-specified due to inadequate data on which materials and designs optimise performance.
May 16, 2025
Array Technologies has unveiled its latest tracker, designed for use in regions prone to high wind speeds and significant hailstorms.
May 14, 2025
Silfab Solar has raised US$110 million through the sale of Section 45X Advanced Manufacturing Production Tax Credits (PTCs).

Subscribe to Newsletter

Upcoming Events

Solar Media Events
June 17, 2025
Napa, USA
Upcoming Webinars
June 30, 2025
10am PST / 6pm BST
Solar Media Events
July 1, 2025
London, UK
Solar Media Events
July 1, 2025
London, UK
Solar Media Events
July 8, 2025
Asia