Innovative researchers at HKUST have introduced a molecular technique to enhance both the efficacy and resilience of perovskite solar cells, potentially easing the proliferation of renewable energy technologies on a large scale.
Photovoltaic (PV) technologies, which convert light into electricity, are increasingly utilized worldwide for generating renewable energy. Scientists at the School of Engineering at the Hong Kong University of Science and Technology (HKUST) have formulated a molecular treatment that significantly enhances the efficiency and lifetime of perovskite solar cells. This advancement holds promise for accelerating the mass production of this clean energy source.
A pivotal aspect of the solution was their successful identification of crucial factors that influence the performance and lifespan of halide perovskites, an advanced photovoltaic material that has emerged as one of the most promising materials in PV devices due to its unique crystal structure. The results have been published in Science.
Under the leadership of Assistant Professor Lin Yen-Hung from the Department of Electronic and Computer Engineering and the State Key Laboratory of Advanced Displays and Optoelectronics Technologies, the research team explored various methods of passivation, a chemical process that reduces the number of imperfections or lessens their impact on materials, thereby enhancing the functionality and longevity of devices containing these materials. Their focus was on the “amino-silane” molecular group for passivating perovskite solar cells.
Elevating Solar Cell Efficiency and Longevity
“Passivation in various forms has played a crucial role in enhancing the efficiency of perovskite solar cells over the past decade. However, passivation approaches that lead to the highest efficiencies often do not significantly bolster long-term operational stability,” Prof. Lin highlighted the issue.
For the first time, the research team demonstrated how different categories of amines (primary, secondary, and tertiary) and their combinations can enhance the surfaces of perovskite films where numerous imperfections arise. They accomplished this through both “ex-situ” (outside the operational environment) and “in-situ” (inside the operational environment) methods to observe the interactions of molecules with perovskites. Subsequently, they pinpointed molecules that considerably increase photoluminescence quantum yield (PLQY), i.e., the amount of photons emitted during materials’ excitation, indicating fewer imperfections and better quality.
“This strategy is essential for the advancement of tandem solar cells, which incorporate multiple layers of photoactive materials with varying bandgaps. This design optimizes the usage of the solar spectrum by absorbing different segments of sunlight in each layer, resulting in enhanced overall efficiency,” Prof. Lin explained the application.
In their solar cell demonstration, the team fabricated devices of medium (0.25 cm²) and large (1 cm²) sizes. The experiment achieved minimal photovoltage loss across a wide range of bandgaps, maintaining a high voltage output. These devices attained high open-circuit voltages exceeding 90% of the thermodynamic threshold. Comparing against approximately 1,700 data sets from existing literature revealed that their outcome was among the most efficient reported to date in terms of energy conversion efficiency.
Illustrating Operational Stability
In addition, the study showcased exceptional operational stability for amino-silane passivated cells under the International Summit on Organic Solar Cells (ISOS)-L-3 protocol, a standardized evaluation method for solar cells. About 1,500 hours into the cell ageing process, the maximum power point (MPP) efficiency and power conversion efficiency (PCE) remained at elevated levels. The top-performing cells retained 95% of their original values, with the champion MPP efficiency and PCE reaching 19.4% and 20.1%, respectively – representing one of the highest and longest metrics reported to date after considering the bandgap.
Prof. Lin stressed that their treatment methodology not only enhances the efficiency and durability of perovskite solar cells but is also suitable for large-scale industrial production.
“This treatment resembles the HMDS (hexamethyldisilazane) priming process extensively used in the semiconductor industry,” he remarked. “This similarity suggests that our novel approach can be seamlessly integrated into existing manufacturing processes, making it economically viable and primed for widespread application.”
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