Longi achieves 33.5% efficiency with flexible solar cell

• Longi has achieved a power conversion efficiency of 33.5% for its 1cm2 flexible perovskite-silicon tandem solar cell
• Interfacial adhesion is crucial in flexible tandem devices
• The strategy aims to improve interfacial adhesion

Chinese solar panel manufacturer Longi’s flexible solar cell has recorded a power conversion efficiency of 33.5%, far higher than the industry average.

The 1cm2 flexible perovskite-silicon tandem solar cell posted the efficiency rate after being developed through what’s called a dual-buffer layer strategy. This is designed to improve ‘interfacial adhesion’, which is when two different types of material work together on the same surface. 

According to Longi, interfacial adhesion is crucial in flexible tandem devices, such as solar panels, as it makes sure the panel continues to generate power even when it bends. 

The strategy has been certified by the US Department of Energy’s National Renewable Energy Laboratory (NREL). 

Perovskite/silicon tandem solar cells have emerged as promising candidates for next-generation solar technology, according to a report by Nature, due to them being able to generate more power. For context, the average solar panel efficiency is between 18-24%.

However, the report also claimed that the mechanical stress generated during repeated environmental stress cycles remains a critical challenge for flexible perovskite/silicon tandem solar cells, leading to interfacial delamination and device degradation. 

Install solar panels

Solar panels can help cut your energy bills year-on-year, so it's worth the investment. Use the button below to receive free, no obligation quotes from our trusted suppliers.

Get quotes

A spokesperson for Longi was quoted saying that the cell was fabricated on a 60-μm-thick silicon wafer and can be folded in half with a bending radius of up to 15 mm, and weighs 4.38g. 60-μm refers to 60 micrometres, which is equal to 0.06 millimetres or 0.0024 inches. 

The team at Longi applied a first tin oxide buffer to protect the panel during the conducting oxide sputtering process, and was performed via atomic layer deposition, before a second layer was deposited through chemical vapor deposition to reduce resistive losses. 

The panel was tested under standard illumination conditions, helping the 1cm2 tandem cell achieve its 33.35% efficiency, as well as a fill factor of 84.5%. The ‘fill factor’ refers to the amount of power a solar cell generates versus the maximum amount its actual power output. 

The testing from the report also said that based on this dual-buffer-layer, the flexible tandem solar cell, constructed on a 60-micron thick ultra-thin silicon bottom cell, achieves a certified PCE of 33.4% on 1-cm2 area, and an certified PCE of 29.8% on wafer-sized area of 260-cm2 with a power-per-weight of up to 1.77 W/g. 

The modified tandem solar cells kept 97% of their initial power conversion efficiencies after 43000 bending cycles under a maximum curvature radius of around 40 mm in air, and around 97% after thermal cycling testing (−40 °C to 85 °C) for 250 cycles.

Install solar panels

Solar panels can help cut your energy bills year-on-year, so it's worth the investment. Use the button below to receive free, no obligation quotes from our trusted suppliers.

Get quotes

Written By

Tamara Birch Newsletter and sponsored content editor

Tamara is a London-based journalist and has written about environmental topics for more than four years. This includes advising small business owners on cost-effective ways, like solar panels and energy-efficient products, to help them become more sustainable.

She has used her journalist and research skills to become highly knowledgeable on sustainable initiatives, issues, and solutions to help consumers do their bit for the environment – all while reducing monthly costs.

In addition to adopting sustainable practices in her personal life, Tamara has worked in the retail B2B space to help independent retailers think about their environmental choices and how they can help improve their business. She now uses this knowledge to help consumers do the same.

Her passion for sustainability and eco-friendly solutions stems from a long obsession with nature and animals and ensuring they feel looked after. In her free time, Tamara enjoys reading fantasy novels, visiting the gym, and going on long walks in new areas.

More about

Reviewed By

Maximilian Schwerdtfeger Content manager

Max joined The Eco Experts as content manager in February 2024 and became deputy editor in 2025. He has written about sustainability issues across numerous industries, including maritime, supply chain, finance, mining, and retail. He has also written extensively for consumer titles like City AM, The Morning Star, and The Daily Express.

In 2020, he covered in detail the International Maritime Organisation’s (IMO) legislation on sulphur emissions and its effects on the global container shipping market as online editor of Port Technology International.

He also explored the initiatives major container ports and terminals have launched in order to ship vital goods across the world without polluting the environment.

Since then, he has reported heavily on the impact made by environmental, social, and governance (ESG) practices on the supply chain of minerals, with a particular focus on rare earth mining in Africa.

As part of this, in 2022 Max visited mines and ports in Angola to hone in on the challenges being faced by one of the world’s biggest producers of rare earth minerals.

His most recent sustainability-related work came much closer to home, as he investigated the eco-challenges faced by independent retailers in the UK, specifically looking at how they can cut emissions and continue to thrive.

Max lives in South London and is an avid reader of books on modern history and ghost stories. He has also recently learned to play the game Mahjong and takes every opportunity to do so. He is also yet to find a sport he doesn’t enjoy watching.

More about