Perovskite solar cell is a new generation of solar technology. Perovskite compounds can be tuned to respond to different colors in the solar spectrum by changing the material, and have great potential in photovoltaic applications.
The use of lead halide perovskites as a light-absorbing layer to fabricate stable thin-film cells with photoelectric conversion efficiencies exceeding 10%. Solar panels use semiconductor materials in the same way.
1. Industry situation of perovskite solar cell
The photovoltaic industry needs to reduce costs to promote development, and the crystalline silicon route is about to hit the upper limit of theoretical efficiency. The investment cost of perovskite modules is lower than that of crystalline silicon, and the cost of 100MW modules is less than 1 RMB/W.
On the one hand, the conversion efficiency has improved rapidly, and the conversion rate has increased to 31.3%. The tandem battery is also expected to improve the conversion efficiency. On the other hand, the perovskite process flow and engineering improvement cycle is short, technological progress is fast, and the problems of mass production and short service life are expected to be solved.
Perovskite solar cell is more widely used than the crystalline silicon route, and may become the mainstream material in the field of BIPV and electric vehicle roof power generation in the future.
The structure of perovskite thin-film cells is slightly different from the classical structure of crystalline silicon cells. Perovskite solar cell can be fabricated using conventional n-i-p or p-i-n structures, with a perovskite absorber layer sandwiched between a hole transport layer (HTL) and an electron transport layer (ETL), followed by a glass covering the transparent layer.
Chinese factories lead the world in laboratory and mass production. More than 20 manufacturers have deployed perovskite, mainly in the fields of upstream materials, midstream batteries and equipment, and general technologies. GCL Nano’s 100MW perovskite module is scheduled to be put into mass production in 2022. Hangzhou Fiberna Optoelectronics invested 5.46 billion RMB to build a 5GW perovskite plant and officially put it into production.
2. Preparation process of perovskite solar cell
In the entire production process of perovskite solar cell, the links such as coating, etching, and packaging are particularly critical.
As a new type of solar thin film battery, perovskite solar cell is similar to other thin film batteries. It needs to be prepared by solution coating method, solution spraying method, vapor deposition method, etc. The dense perovskite layer film and the transmission film are used to improve the electrical contact between different layer structures, reduce the loss during the transmission process, and achieve high cell conversion efficiency.
The mesoporous structure of perovskite solar cell is FTO conductive glass, TiO2 dense layer, TiO2 mesoporous layer, perovskite layer, HTM layer, and metal electrode. Through multi-channel laser etching, the circuit structure in perovskite cells can be constructed, and multiple perovskite solar cell can be connected in series into components.
The functional layer materials in perovskite solar cell is sensitive to water vapor, oxygen, ultraviolet light, pressure, etc. in the air. When exposed to water, oxygen, or directly irradiated by ultraviolet light, the material will be modified and decomposed, and its function will be lost.
Packaging technology can effectively isolate the working components from the external environment and prevent the pollution and corrosion of various impurities. It is a method to improve the service life of precision electronic components.
At present, there are two common perovskite solar cell packaging technologies:
The first packaging technique uses evaporating metal injectors and soldered metal strips to conduct current from the cell to the outside and seal the edges of the metal strips with the device in the center of the enclosed cavity.
The second encapsulation technique uses a transparent ITO electrode to separate the perovskite from the metal electrode to ensure a certain lateral gap between the electrode and the PSCs. One side of the encapsulation is directly the ITO electrode, which can better seal the entire device.
The above processes involve industrial chains such as raw materials, equipment, and technology. Among them, perovskite is rich in raw material resources, the production process is relatively simple, and the materials are not much, and the barriers are not large. However, the high technical requirements of perovskite solar cell equipment are the main constraints of battery production. The technical requirements mainly involve etching equipment, coating equipment, testing equipment, packaging equipment and so on.
3. Prospects for the use of perovskite solar cell
Perovskite is a crystalline material with high photoelectric conversion efficiency, which is widely used in photovoltaic, LED and other fields. Solar cells made of perovskite-type organic metal halide semiconductors as light-absorbing materials are called perovskite solar cell.
Perovskite, electron transport layer, hole transport layer, etc. constitute a perovskite solar cell. Perovskite solar cell is similar to amorphous silicon thin-film other cells, with a P-I-N structure, where the perovskite material acts as a light absorption layer (I layer) sandwiched between an electron transport layer (N layer) and a hole transport layer (P layer).
Due to the advantages of high conversion rate and low cost, perovskite solar cell are suitable for scenarios such as large-scale power stations. At the same time, due to its thin, flexible and customizable characteristics, it is expected to be widely used in various scenarios such as photovoltaic building integration, electronic consumer products, sensors, and fabrics in the future. Perovskites and their tandem cells have the potential to replace and complement crystalline silicon products.
1. Perovskite solar cell market space
Perovskite solar cell can be made into both rigid battery components and flexible battery components. Based on the excellent characteristics of thin-film batteries and the low-cost advantage of perovskite, flexible perovskite batteries are expected to become BIPV (Building Integrated Photovoltaic System), flexible scenarios (such as wearable clothes/backpacks, tents/power banks and other portable devices) in the future and other mainstream products for differentiated application scenarios.
At the same time, rigid components with perovskite superimposed on crystalline silicon can be applied to ground photovoltaic power stations. Experts predict that the perovskite market share may exceed 29% of the world market in 2030. Currently limited by the capacity of perovskite, the market share of perovskites will slowly rise to 7% by 2025. After 2025, the growth of photovoltaic installations will be limited by the supply of the traditional module market.
In the long run, perovskite has the potential to reduce photovoltaic costs by 80%, coupled with its unparalleled high efficiency. The installed capacity of mining may reach 116.9GW, exceeding 29% of the market share of newly installed photovoltaic capacity that year.
2. Economic analysis of perovskite solar cell
At this stage, the conversion efficiency of perovskite solar cell is lower than that of single crystal silicon cells, so a higher capacity ratio should be given, and the calculation should be based on a capacity ratio of 1.27. The number of perovskite modules will be 1.24 times that of monocrystalline silicon modules, which will lead to a corresponding increase in investment costs such as floor space and brackets, which is also considered as an increase of 24% in the calculation.
4. The rise of perovskites
During the development of thin-film batteries, many emerging technologies have emerged, but most of them are limited by mass production conditions and efficiency, and most of them are difficult to achieve commercialization. Among these emerging technologies, the industrialization prospect of perovskite solar cell is relatively considerable, and it is expected to become a strong competitor of crystalline silicon battery.
According to the data, the theoretical efficiency limit of crystalline silicon cells is 29.4%, and the achievable engineering limit efficiency under practical conditions is 27.1%; and in terms of mass production cells, according to expert’s predictions, by 2030, the efficiency of conventional PERC crystalline silicon cells will be 24.1%.
HJT cell efficiency is 26%, TOPCon cell efficiency is 25.6%, IBC cell efficiency is 26.2%, approaching the engineering limit, while the theoretical limit of perovskite single-junction cell is 33%, which is significantly higher than that of crystalline silicon cells. When perovskite solar cell technology was first used in photovoltaics in 2009, its conversion efficiency was only 3.8%.
The price of silicon material continued to rise, and perovskite ushered in a cost advantage. Since 2020, the silicon material market has ushered in a strong cycle. The price of polysilicon dense material reached 294 RMB/kg. The continuous increase in the price of silicon material has caused a certain degree of decline in the profits of downstream battery and module manufacturers, and a certain degree of decline in the net profit margin.
The perovskite production process does not require silicon material, and the raw materials required for the production of metal halide perovskites are abundant and inexpensive. The component production process does not require a processing temperature of about 1,000 degrees, the energy consumption in the production process is relatively low, and most links do not require a vacuum environment.
Stability is an important factor restricting the industrialization of perovskite solar cells. As the fastest growing photovoltaic technology in history, perovskite solar cell has advantages over crystalline silicon cells in terms of efficiency and cost, but their main disadvantage is their short lifespan. Early perovskite solar cell (PSC) lasted only a few minutes, and current perovskite solar cell has a T80 lifetime (the efficiency drops to 80% of the initial value) of about 4000 hours.
5. Crystalline silicon-perovskite tandem battery
The construction of tandem devices is the most important way to further improve the efficiency of solar cells. In a tandem solar cell, the wide-bandgap top cell absorbs short-wavelength sunlight, and the narrow-bandgap bottom cell absorbs long-wavelength sunlight that is not utilized by the wide-bandgap top cell by using semiconductor materials with different bandgap.
It is possible to reduce the the energy loss caused by the thermal relaxation of carriers in small single-junction cells can also broaden the utilization range of the solar spectrum, thereby improving the conversion efficiency of the cells. The development of double-junction tandem solar cells with ideally matched energy gaps can theoretically achieve a conversion efficiency of more than 44%, which is much higher than the theoretical efficiency of single-junction cells (33%).
Perovskite solar cells can more efficiently use high-energy ultraviolet and blue-green visible light, while silicon solar cells can effectively use infrared light that perovskite materials cannot absorb. Therefore, the combination of two single cells by stacking can break through the theoretical efficiency limit of traditional pure silicon photovoltaic cells and further improve the efficiency of silicon photovoltaic cells.
According to the data, the theoretical efficiency of the new perovskite photovoltaic cell can reach 31% in single layer, the conversion efficiency of perovskite double junction tandem cell can reach 35%, and the theoretical efficiency of perovskite triple junction tandem cell can reach 35%.
The efficiency can reach more than 45%. Therefore, all-perovskite tandem cells have gradually become an important hot spot in the field of photovoltaic research in the world in recent years due to their outstanding advantages such as high efficiency, low cost, and simple preparation process.