Researchers at the Hong Kong University of Science and Technology (HKUST) have developed a new molecular treatment that significantly enhances the efficiency and durability of perovskite solar cells.
This advancement could accelerate the large-scale production of this clean energy technology. The research findings have been published in the journal Science.
Perovskite solar cells are a next-generation photovoltaic (PV) technology known for their unique crystal structure and potential to revolutionize renewable energy.
The research team, led by Assistant Professor Lin Yen-Hung from the Department of Electronic and Computer Engineering, focused on identifying key factors that affect the performance and lifespan of halide perovskites, the material used in these solar cells.
The team investigated various passivation techniques.
Passivation is a chemical process that reduces the number of defects in materials, thereby enhancing their performance and longevity. They specifically studied the “amino-silane” family of molecules for passivating perovskite solar cells.
“Passivation has been crucial in improving the efficiency of perovskite solar cells over the last decade. However, methods that lead to the highest efficiencies often do not substantially improve long-term stability,” explained Prof. Lin.
For the first time, the researchers demonstrated how different types of amines (primary, secondary, and tertiary) and their combinations can improve the surfaces of perovskite films where many defects form.
They used both “ex-situ” (outside the operating environment) and “in-situ” (within the operating environment) methods to observe how these molecules interact with perovskites.
By identifying molecules that significantly increase photoluminescence quantum yield (PLQY), the team was able to indicate fewer defects and better material quality. This approach is essential for developing tandem solar cells, which combine multiple layers of photoactive materials with different bandgaps.
Tandem solar cells maximize the use of the solar spectrum by absorbing different parts of sunlight in each layer, leading to higher overall efficiency.
In their experiments, the team fabricated medium (0.25 cm²) and large (1 cm²) solar cell devices. They achieved low photovoltage loss across a broad range of bandgaps, maintaining a high voltage output.
These devices reached high open-circuit voltages beyond 90% of the thermodynamic limit.
When benchmarked against about 1,700 sets of data from existing literature, their results were among the best reported to date in terms of energy conversion efficiency.
More importantly, the study demonstrated remarkable operational stability for amino-silane passivated cells under the International Summit on Organic Solar Cells (ISOS)-L-3 protocol, a standardized testing procedure for solar cells.
Approximately 1,500 hours into the cell aging process, the maximum power point (MPP) efficiency and power conversion efficiency (PCE) remained at high levels.
The champion MPP efficiency and PCE were recorded at 19.4% and 20.1%, respectively—among the highest and longest-lasting metrics reported to date.
Prof. Lin emphasized that their treatment process not only boosts the efficiency and durability of perovskite solar cells but is also compatible with industrial-scale production.
“This treatment is similar to the HMDS (hexamethyldisilazane) priming process widely used in the semiconductor industry,” he said. “Such similarity suggests that our new method can be easily integrated into existing manufacturing processes, making it commercially viable and ready for large-scale application.”
The team included Ph.D. student Cao Xue-Li, Senior Manager Dr. Fion Yeung, and collaborators from Oxford University and the University of Sheffield.
This breakthrough holds great promise for the future of solar energy, offering a more efficient and durable solution for harnessing renewable power.
