Long-term test shows: Efficiency of perovskite cells varies with the season
Standard perovskite solar cells perform very well during the summer months, even over several years, but decline in efficiency during the darker months.
Helmholtz-Zentrum Berlin für Materialien und Energie
image:
The team has set up a unique measuring station on the roof of a research building at HZB to investigate different solar cells under real weather conditions, including standard perovskite solar cells.
view moreCredit: HZB/ Industriefotografie Steinbach
Scientists at HZB run a long-term experiment on the roof of a building at the Adlershof campus. They expose a wide variety of solar cells to the weather conditions, recording their performance over a period of years. These include perovskite solar cells, a new photovoltaic material offering high efficiency and low manufacturing costs. Dr Carolin Ulbrich and Dr Mark Khenkin evaluated four years of data and presented their findings in Advanced Energy Materials. This is the longest series of measurements on perovskite cells in outdoor use to date. The scientists found that standard perovskite solar cells perform very well during the summer months, even over several years, but decline in efficiency during the darker months.
Small perovskite solar cells on a laboratory scale can now achieve an efficiency of up to 26.95% under standard testing conditions. They are inexpensive and easy to manufacture and first solar cells, based on perovskites are being sold already. However, it is important to understand the long-term behaviour of perovskite solar cells when used outdoors in order to better predict energy yields and service life.
At HZB, Dr Carolin Ulbrich and her team, supported by the HZB-funded TAPAS project with the University of Ljubljana, have set up a large outdoor test station: racks equipped with solar cells and measurement technology are installed on the roof. They are exposed to wind and weather all year round. Measurement data from the past four years from small perovskite solar cells encapsulated in glass are now available. The cells were manufactured at HZB by Eva Unger's team (details on the structure: ITO | 2PACz | Cs0.15FA0.85PbI2.55Br0.45 (band gap of 1.65 eV) | C60 | SnO2 | Cu. ).
The results are encouraging: the peak power remained almost the same in the first two summers, and decreased by only about 2% in absolute terms between the first and fourth summers. However, efficiency dropped by around 30% during the winter months.
The team identified several reasons for this. At higher latitudes, such as at the Berlin site, the spectral distribution of sunlight changes, with a greater proportion of ‘blue’ components in summer and a greater proportion of ‘red’ components in winter. However, perovskite solar cells are primarily capable of converting blue light into electrical energy. In locations closer to the equator, these spectral shifts are less pronounced, meaning perovskite solar cells are likely to deliver a more consistent yield throughout the year. ‘What distinguishes perovskite solar cells from more mature PV technologies is that they often change their efficiency reversibly during the day-night cycle. This property significantly contributes to the large seasonal fluctuations observed,’ says Mark Khenkin.
The evaluation of the data was performed by doctoral student Marko Remec. Together, the team has made an important contribution to understanding the ‘real-world behaviour’ of perovskite solar cells and how it is affected by external conditions.
Journal
Advanced Energy Materials
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Seasonality in Perovskite Solar Cells: Insights from 4 Years of Outdoor Data
Article Publication Date
26-Jul-2025
HKUST partners with top us and swiss universities to propose innovative strategy reshaping stability and sustainability of perovskite solar cells
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Corresponding author Prof. Zhou Yuanyuan (left), holding a crystal model of perovskite, and first author Dr. Duan Tianwei (right) standing in front of solar panels.
view moreCredit: HKUST
A research team from the School of Engineering (SENG) at The Hong Kong University of Science and Technology (HKUST) has introduced comprehensive bio-inspired multiscale design strategies to address key challenges in the commercialization of perovskite solar cells: long-term operational stability. Drawing inspiration from natural systems, these strategies aim to enhance the efficiency, resilience, and adaptability of solar technologies. The approaches focus on leveraging insights from biological structures to create solar cells that can better withstand environmental stressors and prolonged use.
Perovskite solar cells are advantageous due to their low-temperature, solution-based manufacturing process, which has the potential to lower solar energy costs. However, their commercial viability is hindered by several operational issues, including inadequate interfacial adhesion, mechanical fragility, and susceptibility to environmental stressors (e.g., heat, moisture, and UV light). These degradation processes occur across various length scales, from picometers to centimeters, and multiscale structural factors can significantly affect the stability and performance of the final perovskite solar cells.
Rethinking solar cell design through the lens of nature
To tackle the challenges faced by perovskite solar cells, Prof. ZHOU Yuanyuan, Associate Professor in the Department of Chemical and Biological Engineering (CBE) and Associate Director of the Energy Institute at HKUST, along with his research group and collaborators from top institutions in the US and Switzerland, propose leveraging insights from biological systems. They suggest that the hierarchically functional structures found in nature, such as those in leaves, can inspire the development of solar technologies that are efficient, low-cost, resilient, and adaptable to environmental changes.
Multiscale bio-inspired strategy
Their comprehensive strategy spans multiple levels:
- Molecular level: Utilizing bio-inspired molecular interactions for crystallization control and degradation mitigation
- Microscale level: Implementing self-healing and strength-enhancing strategies using dynamic bonds and interfacial reinforcement
- Device level: Adopting functional structures inspired by nature, such as moth eyes, leaf transpiration, and beetle cuticles, to improve light management, heat dissipation, and environmental protection
“Nature provides an abundant reservoir of design solutions to help us build solar materials that can thrive in real-world conditions,” said Prof. Zhou. “We’ve already translated some of these strategies into synthetic energy devices.”
Landmark advances: chiral and laminated interfaces
This vision builds on recent breakthroughs in bio-mimicking interfacial design:
- Chiral-structured heterointerface: Prof. Zhou’s team created a chiral interface using R-/S-methylbenzylammonium, where the helically packed benzene rings mimic biological springs, significantly enhancing the mechanical durability of perovskite solar cells. This work was published in Science.
- Laminate-inspired interface: Prof. Zhou’s team developed a cell-surface-like multi-layer surface microstructure comprising a molecular passivation layer, a fullerene derivative layer, and a 2D perovskite capping layer, which effectively suppresses defects and enhances energy level alignment, resulting in improved efficiency and damp-heat stability. This work was published in Nature Synthesis.
These studies highlight the potential of bio-inspired and hierarchical engineering to address fundamental limitations of perovskite solar cells, including adhesion, fatigue, and interface degradation.
Toward sustainable and scalable solar technologies
The multiscale design framework emphasizes sustainability, prioritizing low-toxicity materials compatible with a circular economy. Prof. Zhou’s team proposes that future research will focus on screening bio-inspired molecules for optimal film crystallization and stability, developing self-healing mechanisms activated by operational stress, designing cost-efficient biomicrostructures, and integrating multifunctional encapsulation to enhance the efficiency and lifespan of perovskite solar cells.
Dr. DUAN Tianwei, the first author and Research Assistant Professor at HKUST’s CBE Department, stated, “This is not just about new materials; it represents a novel approach to solar technology, inspired by nature itself. By integrating bio-inspired structures, functions, and sustainability, we are excited about the new chapter unfolding in solar energy.”
The team’s research work, titled “Bio-Inspired Multiscale Design for Perovskite Solar Cells”, has been published in the prestigious journal Nature Reviews Clean Technology, in collaboration with Yale University, École Polytechnique Fédérale de Lausanne, and Lawrence Berkeley National Laboratory.
Comparison of conventional perovskite solar cells and leaves from a multiscale perspective
Credit
HKUST
Journal
Nature Reviews Clean Technology
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Bio-inspired multiscale design for perovskite solar cells
Article Publication Date
25-Jul-2025
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