Power conversion efficiency (PCE) is the most basic and important parameter of solar cells. In the field of photovoltaics, how to extract more electric energy from solar energy has been a research direction that academia and industry have been diligently pursuing.
Currently, monocrystalline silicon is a commonly used photovoltaic power generation material . However, as the energy conversion efficiency of crystalline silicon cells gradually reaches its theoretical upper limit, scientists have turned their attention to various types of non-silicon cells, among which the photovoltaic industry has emerged. The “popular fried chicken” - perovskite
Compared with the current mainstream crystalline silicon cells, perovskite has the advantages of higher theoretical efficiency and lower expected cost. Therefore, it is a revolutionary new material for the photovoltaic industry.
Perovskite batteries are mainly divided into single junction and stacked structures. The single junction perovskite battery structure is a 5-layer structure similar to a "sandwich" layer, with a simple structure and a theoretical photoelectric conversion efficiency of up to 33%. It is also the first choice for research on perovskite enterprises in China. At present, the highest single junction efficiency of perovskite has reached 25.7%, achieved by the National Institute of Science and Technology (UNIST) in Ulsan, South Korea.
The theoretical efficiency upper limit of the stacked structure is high, with a conversion efficiency of 45% for double layered perovskite and 50% for triple layered perovskite. At present, the efficiency of the perovskite/crystalline silicon double layered battery has reached 32.5%, which was certified by the German HZB Research Center in December 2022.
The main advantages of perovskite
1. High energy conversion efficiency
For a considerable period of time in the past, crystalline silicon photovoltaic cells were a perfect combination of cost and efficiency. Accompanying this is the limitation of the efficiency of natural minerals in converting solar energy. 29.43% of the theoretical limit value serves as a barrier for crystalline silicon materials from one glance to the end.
In sharp contrast, perovskite has walked out of the "steepest growth curve". In 2009, Japanese scientists first used perovskite photovoltaic cells for power generation, with an energy conversion efficiency of only 3.8%. In just the past 13 years, today the laboratory efficiency of perovskite batteries has basically caught up with the results achieved by more than 60 years of development of crystalline silicon, reaching 25.7%. Moreover, the theoretical efficiency of the single-layer perovskite battery can reach 33%, and the double-layer can reach over 45%, which has a higher room for improvement than crystalline silicon.
It is not an exaggeration to say that perovskite has completed the fifty year journey of crystalline silicon batteries in ten years. Behind this development speed is the fact that perovskite materials have far stronger absorption properties than crystalline silicon, and the extremely low energy loss during energy conversion is also related to their wide spectral coverage.
2. Low cost and short preparation process
The raw materials for perovskite batteries are all basic chemical materials, artificially synthesized, and do not contain rare elements, making them cheaper and easier to obtain compared to the silicon materials for crystalline silicon batteries.
Except for unrestricted raw materials, the preparation process of perovskite batteries is relatively short. The entire industry chain, from glass, film, target materials, chemical raw materials to component molding, can be highly concentrated in a 100 megawatt factory within 45 minutes.
In addition, perovskite materials have low sensitivity to impurities, lower purity requirements for raw materials than crystalline silicon, and can be prepared at low temperatures. Compared to the high-temperature process of about 1000 degrees Celsius for crystalline silicon, the temperature of the perovskite production process does not exceed 150 degrees Celsius, which saves resources and reduces energy consumption.
3. Wide application prospects
At the power station end, perovskite batteries meet market demands for long-term power generation, transparency, and aesthetics due to their low light intensity and customizable colors. They also have broad market space in BIPV, curtain walls, and sunrooms.
The main defects of perovskite
No material is perfect, and the same goes for perovskite. Although perovskite batteries have many advantages, as a material that has not yet left the laboratory stage, their defects seriously limit their ability to be put into industrial production, and therefore cannot effectively replace monocrystalline silicon batteries.
1. Stability issues
Due to the fact that perovskite materials belong to ionic crystals, their crystal stability is not as good as that of crystalline silicon, which can easily lead to the fragility of perovskite batteries. There may be problems such as high temperature resistance, poor light resistance, easy hydrolysis, and oxidation. The earliest perovskite batteries could only last for a few minutes. If a perovskite battery is used for one or two years and its efficiency decreases by 20%, then there is no economic value.
2. Lead containing toxic substances
In the composition and structure of perovskites, lead is currently necessary for high-performance perovskites, but this has also become another criticized drawback, which may have adverse effects on human health. In addition, calcium minerals can also dissolve in water, and once precipitated into the surrounding environment, it will undoubtedly cause significant pollution.
3. Difficult to prepare on a large scale
Although the preparation of perovskite materials is simple and cost-effective, the current perovskite batteries still have problems in large-scale equipment and mass production processes.
On the one hand, it is due to the immaturity of coating technology. High efficiency perovskite batteries prepared in the laboratory are mostly small area thin films below 1 square centimeter, which are mostly prepared by spin coating method. In large-scale production, the slit coating method is used, and the perovskite layer cannot be uniformly applied on the surface of the equipment, which has a significant negative impact on device performance. Therefore, better spraying processes need to be developed.
On the other hand, perovskite commonly uses TCO (transparent conductive oxide) thin films to collect current, and some physical properties of such materials can cause light loss, which becomes more pronounced with the increase of area, resulting in a significantly lower efficiency of perovskite components compared to single cell batteries.
In short, due to various reasons, the conversion efficiency of perovskite batteries often deteriorates severely with increasing area.
Since entering the field of solar cells, perovskite materials have firmly focused on the "ceiling" of silicon conversion efficiency, initiating an "efficiency revolution".
Although the three major issues mentioned above currently constrain the development of perovskite, they are also directions for continuous breakthroughs in the industry. Since the beginning of this year, there have been continuous positive signals, with multiple large-scale pilot projects for calcium titanium ore being launched and industrialization accelerating.
Against the backdrop of the "dual carbon" policy, the proportion of photovoltaic energy consumption in primary energy will increase from less than 1% to over 25% in the future, indicating promising prospects for the photovoltaic market. Perovskite photovoltaics, as an emerging photovoltaic technology, not only have laboratory efficiency comparable to that of monocrystalline silicon photovoltaics, but also have significant advantages in cost and process. In addition, perovskite photovoltaics have excellent weak light performance and adjustable photoelectric characteristics, which are characteristics that crystalline silicon photovoltaics do not possess. This makes perovskite photovoltaics more imaginative in application scenarios, and is expected to bring photovoltaic applications into thousands of industries and households in the future.
Source of copy: Perovskite materials and devices
E-mail: info@chemborun.com
Tel: +86-574-87178138 
No. 1558, Jiangnan Road,, Ningbo, Zhejiang, China (Mainland)/31
