Faced with the dual pressures of global warming and the increasingly dangerous ecological environment, various countries are focusing on the development of renewable energy to jointly respond to global climate change. Solar photovoltaic power generation , as the main force in the development of renewable energy in the future, has received more and more attention.
With the advancement of technology, the photoelectric conversion efficiency of single-junction perovskite solar cells has increased to 25.7%, which is close to the laboratory's highest efficiency of silicon solar cells . Due to its advantages such as low cost, easy processing, lightweight, flexibility, and sustainability, it has continued to become the most potential new product in the field of photovoltaic in recent years.
However, poor work stability is still the "bottleneck" problem that prevents it from being used in industrial applications. At present, most of the lifespan of perovskite solar cells (Perovskite Solar Cells, PSC) can be maintained at hundreds to thousands of hours, but this is still far from the industry’s vision of “20 years of service life”.
(Source: Princeton University)
The Princeton University team recently developed the most stable PSC to date. Its lifespan has been increased from a thousand hours to ten thousand hours (years). For the first time, inorganic materials are used in each functional layer of the PSC. (Including 2D buffer layer). Moreover, they also demonstrated the first new method of accelerated aging test of PSC, which provides new ideas for the structural design of high-stable PSC in the future.
Recently, a related paper titled "Accelerated aging of all-inorganic, interface-stabilized perovskite solar cells" was published on Science [1]. The first author of the paper is Zhao Xiaoming, a postdoctoral researcher in the Department of Chemical and Biological Engineering at Princeton University, and the corresponding author is Professor Lynn Loo of the School of Engineering at Princeton University.
▲Picture丨Related papers (Source: Science)
The reviewer commented: "This is the first study that applies the concept of acceleration stability experiments to directly calculate the acceleration ratio to perovskite solar cells. This method Helps to reasonably predict the service life of this emerging photovoltaic cell
PSC. Under the condition of 35℃, the life of continuous operation is more than 5 years.
Lu Yueling’s research group has long focused on the stability research of perovskite solar cells, striving to understand the degradation mechanism of perovskite solar cells, and on this basis, developed improved its stability strategy.
Previously, the team conducted a series of studies on the stability of PSC, including the influence of precursor solution on the stability of perovskite [2, 3, 4], and the stability of two-dimensional perovskite when used as a light absorbing layer. Research [5,6], the impact of organic semiconductor additives on the stability of perovskite solar cells [7], the impact of charge transport layer materials on the stability of perovskite solar cells [8,9], etc.
▲Picture丨Zhao Xiaoming (Source: Zhao Xiaoming)
Zhao Xiaoming is mainly responsible for the design of the experimental plan, as well as some characterization and analysis in this study. Based on his understanding of PSC degradation mechanisms from previous work, he designed dozens of different PSCs and tested the lifespan of different PSCs with his team. Through layer-by-layer screening, the new PSC structure has begun to take shape. It is worth noting that all its functional layers are inorganic materials, and each functional layer is stable on its own.
However, it is not "done" that all the materials are stable. The solar cell assembled with them is not stable. Zhao Xiaoming found that this was due to the chemical interaction between adjacent functional layers, which led to the degradation of the battery.
In order to prevent the degradation of PSC due to the interaction of various functional layers, the team specially designed a new type of all-inorganic two-dimensional buffer layer (thickness equivalent to A few atoms () to block chemical components from moving between the two layers.
"It is this thin buffer layer that greatly improves the life of the PSC." He said. According to the paper's results, they also increased the power conversion efficiency of the all-inorganic PSC to 17.4% from the previous 14.9%.
He pointed out that although the current lifespan of PSCs has not yet reached commercial standards, researchers in the field are gradually paying attention to the lifespan of PSCs. They have discovered many important degradation mechanisms and proposed some measures to improve stability. . The lifespan of PSCs is also gradually improving, from just a few minutes at first to hundreds or even thousands of hours today.
(Source: Princeton University)
Therefore, Zhao Xiaoming and his team also began to think about, as PSC becomes more and more stable, how to test its lifespan within a reasonable time range? Scientists hope that the PSC will have a 20-year service life, but considering the real time cost, it is not possible to actually test the battery for 20 years. Therefore, an accelerated aging method must be developed to test its longevity.
In fact, there is a mature accelerated aging test system for the life of silicon batteries internationally. It usually takes a few days or weeks of testing to predict its life in the next 20 years. However, there is currently no accelerated aging testing system for PSCs. "Therefore, we want to develop a reliable accelerated aging test system specifically for PSC to predict its lifespan." Zhao Xiaoming said.
According to reports, this study reported the accelerated aging of perovskite batteries for the first time. However, in previous studies, there was not much information for the team to refer to on the construction of the corresponding accelerated aging test platform. "In order to realize this platform, I asked a lot of advice from my colleagues who work on accelerated aging of organic photovoltaics. After repeated debugging and experiments, my colleagues and I finally successfully built an accelerated aging test platform," he said.
In addition, Zhao Xiaoming and his team selected several PSCs that performed well under normal aging conditions and conducted accelerated aging research. After the battery is ready, they put it into this accelerated aging system for testing and then analyze the data. After the battery is degraded, it is taken out for other characterizations to obtain its degradation mechanism.
▲Figure丨Device structure and photovoltaic characteristics (Source: Science)
The team conducted an in-depth exploration of the accelerated aging of organic solar cells (another new type of solar cell). Based on their previous experience, according to PSC Based on a unique degradation mechanism (ion migration), an accelerated aging test system is designed specifically for PSC.
They choose temperature as the acceleration condition. The degradation of PSC is accelerated by high temperature, and then the acceleration index is derived according to the Arrhenius thermal activation relationship, and then the life span of PSC at normal temperature is deduced through the acceleration index. Using this method, the team predicted that the PSC has an intrinsic life of 51,000 ± 7,000 hours (over 5 years) in continuous operation at 35°C (95°F). "This can be equivalent to a 30-year service life in the external environment." Zhao Xiaoming said.
will enrich the accelerated aging test system of PSC to meet the commercialization needs of the market.
Regarding the follow-up research of this study, on the one hand, the team plans to continue research on the accelerated aging of PSC in different systems to enrich the accelerated aging test system of PSC; on the other hand, aspects, they also further improved the PSC Efficiency and stability are the goals to make it more suitable for commercialization needs.
Zhao Xiaoming said, “The accelerated aging stability test system using temperature can be used to conduct PSC using other parameters (such as strong light or electrical bias). Research on accelerated aging, and provide reference for the development of accelerated aging test systems for other types of solar cells.”
▲Figure丨Characterization of the two-dimensional perovskite coating (Source: Science)
At present, many start-ups have emerged at home and abroad. Attempts to industrialize PSC. Although no commercial products of PSC have been released so far, with the gradual breakthrough of technology, civilian PSC The product is worth looking forward to.
Zhao Xiaoming believes that the technological breakthroughs required for the commercial development of PSCs include the following four points:
First, solve the problem of PSC lifespan. “As the field pays more and more attention to this problem, I believe we will soon see PSCs with a lifespan that meets commercialization standards,” he said.
Second, the optimization of large-volume and large-area production processes. is different from the small-area PSCs in the laboratory. PSCs used in the real world are large-area solar modules. Currently in the laboratory, when preparing large-area PSCs or modules, their performance generally drops to a considerable extent compared to small-area PSCs. Therefore, there is a need to further optimize the scale-up production process of PSCs.
▲Picture丨Accelerated aging of PSC operating at high temperatures (Source: Science)
Third, PSC manufacturing costs are further reduced. Compared with silicon cells and other commercial battery technologies, the advantage of PSC is that it can be produced at low temperatures and therefore consumes less energy. On this basis, further reducing the cost of key materials and further simplifying the preparation process of PSC can further reduce the cost of PSC, thereby gaining an advantage in the market competition with other solar cell technologies.
Fourth, the commercialization of “special” PSCs. Zhao Xiaoming believes that benefiting from the adjustable band gap of perovskite, scientists can design perovskites that only absorb light of specific wavelengths, thereby adjusting the color of the perovskite and even making perovskite solar cells transparent. shape, which silicon cells cannot do.
Recently, Zhao Xiaoming and his team also reported a "special" PSC, which is completely transparent in appearance and looks almost the same as glass, but it can be used to generate electricity [10]. "If all the exterior glass of high-rise buildings in the future is replaced by PSC like ours, the electricity generated every day will be considerable. This will also be more conducive to people's response to the energy crisis. I think this special PSC will also be popular. The market and consumers welcome it," he said.
Down-to-earth, will continue PSC related research
"Perovskite solar cells have great application prospects. I hope to have a deeper understanding of this technology and try to use what I have learned to make some contributions to its development." With this idea , Zhao Xiaoming started his scientific research path.
He graduated from School of Chemical Engineering, Tianjin University with a bachelor's degree and a master's degree, and his mentor was Professor Wang Shirong. During his doctoral studies, he studied at Queen Mary, University of London, under the tutelage of Professor John Dennis. After graduating from the Ph.D., he came to the Department of Chemical and Biological Engineering at Princeton University to conduct postdoctoral research until now. His co-supervisor is Professor Lu Yueling.
▲Picture丨Zhao Xiaoming and his team (Source: Zhao Xiaoming)
He believes that he should pay attention to his ability to think independently, and then also learn how to communicate with colleagues and mentors. More importantly, scientific research must be conducted in a down-to-earth manner.
Next, Zhao Xiaoming and his team will continue their research on PSCs. This time they discovered many interesting phenomena by comparing the lifespans of PSCs with different structures. “We are preparing corresponding papers and hope to share these unexpected findings with colleagues in the field,” he said.
Reference:
1.Xiaoming Zhao et al. Science (2022). https://www.science.org/doi/10.1126/science.abn5679
2. Adv. Funct. Mater. 2018, 28, 1801508
3. Chem. Mater. 2019, 31, 6, 2114–2120
4.J. Phys. Chem. C 2020, 124, 27, 14496–14502
5.Nano Lett. 2020, 20, 12, 8880–8889
6.Adv.Mater. 2022, 34, 2105849
7.Adv.Mater. 2019, 31, 1904494
8.Energy Environ. Sci., 2020,13, 4334-4343
9.Adv. Mater. Interfaces 2021, 8, 2100505
10.Tianran, Xiaoming Zhao et Liu al. Advanced Energy Materials(2022).https://doi.org/10.1002/aenm.202200402
