A pioneering study highlights the critical role of barrier films in shielding flexible solar modules from harsh environmental conditions

Flexible perovskite solar cells are promising for lightweight and versatile applications but their sensitivity to humidity and temperature poses a challenge to long-term durability. To address this, researchers from Japan have conducted a comprehensive study to test the degradation of these solar modules under extreme heat and humidity. Through accelerated testing, they identified how the water vapor transmission rates of barrier films affect the module’s stability, giving critical insights for development of durable solar cells.

Perovskite solar cells (PSCs) present a revolutionary leap in renewable energy technology with their high efficiency, lightweight, and flexible nature. But their commercial applications are often hindered by their sensitivity to environmental factors like heat and humidity.

To address this, a team of researchers led by Professor Takashi Minemoto, a Ritsumeikan Advanced Research Academy Fellow from the College of Science and Engineering, Ritsumeikan University, Japan, along with Dr. Abdurashid Mavlonov from the Research Organization of Science and Technology, Ritsumeikan University, and Dr. Akinobu Hayakawa from Sekisui Chemical Co., Ltd., recently conducted pioneering research to investigate the durability of these PSC modules in harsh environmental conditions. This study was made available online on December 17, 2024, and was published in Volume 286 of Solar Energy on January 15, 2025.

Explaining the motivation behind this study, Prof. Minemoto says, “Perovskite solar cells stand out as particularly promising due to their low-temperature wet-coating process and compatibility with flexible substrates, offering unique opportunities for the solar industry. However, the stability of perovskite is weak compared with conventional material, which can be improved by fabrication processes such as encapsulation with barrier films.”

To analyze the durability of flexible PSC modules, the research team utilized PSC modules made of methylammonium lead iodide (MAPbI₃), which were encapsulated with polyethylene terephthalate substrate having barrier films of varying water vapor transmission rates (WVTR). The PSC modules were subjected to a damp heat test, which utilized exposure of the modules to 85 °C temperature and 85% relative humidity. The conditions were thus set to simulate real-world outdoor conditions over extended periods.

After 2,000 hours of exposure, the photovoltaic (PV) performance of the modules was recorded, and the degradation of the modules was confirmed through characteristics of current voltage, spectral reflectance, and electroluminescence.

The researchers found that high humidity led to the decomposition of the MAPbI₃ layer into lead iodide, blocking the charge transport across layers. This degradation led to a significant reduction in the efficiency of the PSC modules highlighting the detrimental impact of moisture on the PSC performance.

In addition, the findings revealed that the quality of the barrier film played a critical role in the module’s stability. Notably, the module with the lowest WVTR barrier of 5.0 × 10⁻³ g/m²/day retained 84% of its power conversion efficiency. However, the modules with higher WVTR experienced rapid degradation, ceasing to function after just 1,000 hours.

“Our study is the first to report the durability of encapsulated flexible MAPbI3-based PSC modules. When considering solar energy applications for walls and rooftops with weight limits or for mobile platforms, flexible PSCs are a great alternative to the traditional silicon panels. Insights from our study could help industries optimize these modules for highly stable and durable constructs,” explains Prof. Minemoto.

This study highlights the importance of barrier films in maintaining the long-term durability of flexible PSC modules, revolutionizing the PV industry. Additionally, by offering energy generation at multiple locations, these innovations can help reduce strain on power grids. Furthermore, improving the durability of PSC modules could also expand the use of renewable energy since it would allow the deployment of PSC modules in diverse environments, thus accelerating the global shift towards cleaner energy and a sustainable future.

Title of original paper: Perovskite solar cell modules: Understanding the device degradation via damp heat testing
Journal: Solar Energy
DOI: 10.1016/j.solener.2024.113174

About Professor Takashi Minemoto from Ritsumeikan University, Japan

Dr. Takashi Minemoto is a Professor at the College of Science and Engineering, Ritsumeikan University, Japan, and a Ritsumeikan Advanced Research Academy Fellow. He received his Ph.D. from Ritsumeikan University in 2001. His research group deals with the development of next-generation, high-performance solar cells. With over 25 years of experience, Prof. Minemoto has authored 271 publications, contributing significantly to the development and improvement of solar technologies.

Funding information

This work is partly supported by NEDO (the New Energy and Industrial Technology Development Organization) in Japan.