Analysis of Investment Opportunities in New PV Materials - Gap Light-Guiding Film Materials
In the international market, according to data from Trend Force, the neutral forecast for global new PV installed capacity in 2024 is 474 GW, a year-on-year increase of 16%. Compared with the 59% growth rate in 2023, the growth rate has slowed down significantly.
In the domestic market, according to data from the National Energy Administration, in the first half of 2024, the new PV installed capacity reached 102.48 GW, a year-on-year increase of 30.7%, which was significantly narrower than the full-year growth rate of 2023. InfoLink Consulting predicts that China's PV demand in 2024 will be between 240-260 GW. Although the growth rate is far lower than that of last year, it can still maintain a growth of 4-13%.
After the large-scale implementation of capacity expansion plans in 2023, coupled with the slowdown in global demand growth, phased overcapacity has led to a significant decline in the unit prices of products across the entire PV industry chain. The price of upstream N-type silicon material dropped from a high of approximately 200,000 yuan/ton in 2023 to below 40,000 yuan/ton; mid-stream TOPCon cells fell from about 0.8 yuan/W to about 0.28 yuan/W; downstream N-type modules dropped from nearly 2 yuan/W to about 0.7 yuan/W.
On November 15, 2024, the Ministry of Finance and the State Taxation Administration announced that the export tax rebate rate for some PV products would be reduced from 13% to 9%, taking effect from December 1, 2024. This policy adjustment covers PV products such as wafers, cells, and modules. It is expected to increase the cost of exported cells and modules, which will directly reduce the profits of PV enterprises in the short term. However, it is also expected to accelerate the survival of the fittest in the industry and promote the improvement of PV supply.
The PV industry has never stopped technological innovation and iteration since its initial development, which is the internal reason why the PV industry can still maintain strong vitality even after experiencing multiple rounds of large-cycle fluctuations. In 2024, leading enterprises continued to improve cell conversion efficiency from various dimensions such as raw materials, cells, manufacturing processes, and module design to build new-quality productive forces. Certified by the European Solar Test Installation (ESTI), the photoelectric conversion efficiency of the crystalline silicon-perovskite tandem solar cell developed by Longi Green Energy reached as high as 34.6%; certified by an authoritative international third-party testing organization, the photoelectric conversion efficiency of the TBC cell independently developed by Longi reached 27.00%; certified by the Institute for Solar Energy Research Hamelin (ISFH) in Germany, the photoelectric conversion efficiency of the HBC cell independently developed by Longi reached 27.30%; certified by the National Metrology and Testing Center for the PV Industry, the certified conversion efficiency of JinkoSolar's TOPCon reached a maximum of 26.89%.
To sum up, although the PV industry as a whole is in a cyclical downward period in 2024, facing challenges such as phased overcapacity and a significant drop in prices, in the long run, the logic of pursuing clean energy and driving the growth of the PV industry has not changed, and the industry's original aspiration of adhering to technological innovation and forging ahead has not changed. It is believed that with the clearance of capacity and the improvement of the supply-demand structure, the PV industry will usher in a new inflection point.
Cost reduction and efficiency improvement are long-term themes in the development of the PV industry, and technological innovation can be roughly divided into two categories:
(1) Cell technological innovation. The development from polycrystalline silicon cells to monocrystalline silicon cells: due to the high integrity and purity of the crystal structure of monocrystalline silicon cells, the recombination rate of electrons and holes is low, so the photoelectric conversion efficiency is higher; the development from P-type cells to N-type cells: the minority carrier lifetime of N-type cells is significantly higher than that of P-type cells, which can greatly improve the open-circuit voltage and short-circuit current of the cell, resulting in higher cell conversion efficiency; the development from front grid cells to back-contact (BC) cells: since all the metal electrodes of BC cells are arranged on the back, there is no grid line shielding on the front surface, and it has a 100% light-receiving area, maximizing the use of sunlight irradiating its surface.
(2) Module technological innovation. The replacement of ordinary modules with double-sided double-glass modules increases back-side power generation; the replacement of EVA with POE film encapsulation: since the water vapor transmission rate of POE film is much lower than that of EVA film, it greatly improves the weather resistance of PV modules; the replacement of glass backsheets with transparent backsheets significantly reduces the weight of modules and lowers the costs during transportation and installation.
With the replacement of P-type PERC cells by N-type TOPCon cells, a round of main-line technological iteration has been completed. Coupled with the significant decline in the prices of products across the entire PV industry chain in this round, the current cost reduction and efficiency improvement of PV have entered a refined stage. The improvement of conversion efficiency has entered a stage of 0.1% per year, and the cost competition has also entered a stage of a few cents per watt.
Silicon-based PV modules are formed by placing cells on a glass backsheet and then connecting them in series and parallel. Therefore, there are 1-4 mm gaps between cells and between cell strings. These gaps account for 3-10% of the area of the PV module. The sunlight irradiating these gaps directly penetrates the module, resulting in a waste of light energy. To improve the utilization rate of light energy, the industry has begun to adopt the glazed grid glass solution or the gap light-guiding film solution to re-reflect the sunlight at the gaps to the surface of the cells for absorption and power generation, thereby finely improving the module power.
The basic working principle of the gap light-guiding film is shown on the left side of Figure 1. The gap light-guiding film is attached to the backsheet glass, located between cells or between cell strings. The sunlight in the gap area between cells irradiates the microprism structure of the gap film, is directionally reflected to the front glass, and then the total reflection principle at the interface between glass and air is used to reflect the light back to the surface of the cells for absorption and power generation, enabling the secondary use of light. Figure 2 shows the situation where laser light is irradiated on the gap light-guiding film and the light is reflected to the surface of the cells.
The basic structure of the gap light-guiding film is shown on the right side of Figure 1. The gap film uses PET as the base film. One side is coated with hot-melt adhesive for adhesion to the backsheet glass during use; the other side is coated with resin, and a special microprism structure is formed through mold embossing. To achieve a better light-guiding effect, a metal layer is usually evaporated on the surface of the microprism to enhance the light reflection efficiency. Finally, to reduce the potential risk of cell short-circuit caused by the metal coating after film pasting, a transparent insulating layer can be coated on the surface of the metal coating for protection. Figure 3 shows the product form of the gap light-guiding film after being rolled into a coil.
Figure 1: Schematic Diagram of the Principle and Structure of Gap Light-Guiding Film
Figure 2: Physical Image of Gap Light-Guiding Film Application
Figure 3: Physical Image of Gap Light-Guiding Film
Technically, the barriers of gap light-guiding film are divided into the following aspects:
The microstructure of the gap light-guiding film needs to be precisely controlled to maximize the reflection and refraction of light, thereby improving the utilization rate of light energy. This involves complex optical simulation and design to ensure that the propagation and absorption of light inside the module achieve the best effect. Specifically, the key factors such as the size, shape, and angle of the microprism all require a large number of optical simulations and experimental tests. In terms of technical exploration and industrialization practice in this field, the US-based 3M Company is at the global leading level.
The performance of the gap light-guiding film also largely depends on the selection and modification of its materials. (1) Back adhesive layer: In addition to selecting a good main resin, it also needs to undergo high-temperature graft modification, and add additives such as cross-linking agents, light stabilizers, cross-linking aids, and coupling agents. This ensures that it not only has good adhesive strength but also does not accumulate bubbles or slip during the lamination process, and maintains good transparency, temperature resistance, and humidity resistance during the module aging process, without delamination at hot spots or yellowing under UV radiation. (2) Resin prism: As the main functional layer of the light-guiding film, to achieve good processability, excellent temperature resistance, and aging resistance, it is necessary to try different formulations, introduce multi-functional groups, and reasonably control the cross-linking degree of the coating resin.
The gap light-guiding film goes through multiple process steps from the base film to the finished product and requires a large number of special equipment. The thickness of each film layer ranges from a few micrometers to tens of micrometers, which requires high coating precision, large size, high cumulative error requirements, and difficult control of coating quality. Among them, the 5-10 micrometer diagonal microprism process has the highest difficulty. In addition, the metal coating process requires the cooperation of multiple materials and equipment to ensure high density and high weather resistance. The narrow-band slitting process is also a unique precision slitting process in the industry, which needs to balance cost while ensuring quality and processing precision.
In fact, the issue of light energy utilization between cell pieces and cell strings of modules has long been concerned and attempted to be solved by the industry. In recent years, solutions such as glazed grid glass, metal gap light-guiding film, and non-metallic gap light-guiding film have been developed.
Taking a 72-cell module with a power of 590 W as an example, the module size is approximately 2.58 square meters. Calculated based on the gap between cells and between cell strings both being 1.5 mm, the gap area is approximately 0.05 square meters, accounting for about 2%. According to theoretical simulation and experimental data, compared with the ordinary glass solution, the use of the metal gap light-guiding film solution can increase the module power by about 1.5%, which is an increase of approximately 9 W in power. Calculated based on the module price of 0.8 yuan/W, this is equivalent to an increase of 7.2 yuan in sales revenue per module.
Due to the limitation of the slitting precision of the gap film, the processing difficulty of an excessively narrow gap film increases significantly, resulting in poor economic efficiency. Therefore, if calculated based on a width of 4-5 mm, each module requires an area of approximately 0.15-0.2 square meters of gap film. Calculated based on the price of the metal gap light-guiding film of 20 yuan/square meter, this is equivalent to an increase of 3-4 yuan in cost per module. (Note: The above data are all estimated values obtained from public information or expert interviews).
Coating a grid-like ceramic glaze on the backsheet glass to form a grid-like light-guiding area between cells and between cell strings is also a solution to improve the light energy utilization rate at the gaps, and it has achieved large-scale promotion and application earlier than the gap light-guiding film solution. Due to its high technical maturity, coupled with the significant price reduction of all products in the PV industry chain in this round, the current cost increase per module using the glazed grid glass solution is approximately 3 yuan, which is slightly lower than that of the gap light-guiding film.
However, the light irradiated on the ceramic glaze surface forms diffuse reflection, and the reflection efficiency is lower than the directional reflection formed by the gap light-guiding film solution. Therefore, compared with the glazed grid glass, the gap light-guiding film can increase the power of each module by approximately 3 W, which is an increase of 2.4 yuan in sales revenue.
In addition, due to the stress generated during the tempering process after coating the glaze on the glazed grid glass, its impact resistance is weaker than that of the gap light-guiding film solution. Especially under the trend of thinner PV glass, modules using the gap light-guiding film solution have a lower panel breakage rate and higher reliability during transportation, installation, and actual operation.
If the gap light-guiding film solution is adopted, there are currently two types of products: aluminum-coated metal light-guiding films and light-guiding films without metal coating. According to public information, due to the higher light-guiding efficiency of the metal layer, the power increase of the metal gap light-guiding film solution for each module is more than 3 W higher than that of the non-metallic solution, which is equivalent to an increase of more than 2.4 yuan in sales revenue; however, the cost is also more than 1.5 yuan higher. Overall, the comprehensive benefit of the metal film is higher than that of the non-metallic film. Especially in the context where module manufacturers pursue higher power, it may be a better choice.
As a new material used in PV modules on a large scale, the gap light-guiding film is also undergoing continuous technological iteration and performance optimization. In addition to pursuing narrower and thinner sizes and more durable materials, the next generation of innovative products has also emerged in terms of structure. As shown in Figure 4, to further improve the light energy utilization efficiency of the gap light-guiding film, a new generation of "dual-configuration" products has emerged. Microprism light-guiding structures are coated and processed on both the upper and lower surfaces of the PET base film. The addition of the back prism structure conducts part of the transmitted light to the lower surface of the cell, making it more suitable for improving the power of double-sided modules.
Figure 4: Structure Diagram of the New-Generation "Dual-Configuration" Gap Light-Guiding Film
The gap light-guiding film technology was first developed by the internationally renowned new material enterprise 3M Company of the United States. Domestic PV module manufacturers have gradually introduced and applied it in batches in the past two years. Due to China's leading position in the global PV industry in terms of overall strength and the particularly fierce competition, the industrialization of new technologies and new materials still depends on domestic manufacturers. According to public information, we have sorted out the introductions of major suppliers of gap light-guiding film products, as shown in Table 1 below.
Table 1: Enterprises Related to Gap Light-Guiding Film
Source: Company official websites, collation of public information
The rapid development of the PV industry in the past two decades has been mainly driven by continuous technological innovation. Even when the PV industry is in a cyclical trough, new PV technologies and new materials are still emerging in an endless stream, which may be an opportunity for investment layout at a low point.
By eliminating the main grid of the cell, the 0BB technology significantly reduces the single consumption of silver paste and lowers the manufacturing cost; it also reduces the light-shielding area on the cell surface, increases the light-receiving area, and thereby improves the power generation efficiency of the cell. It is becoming one of the mainstream technologies in the PV industry. "Welding + dispensing" is one of the main solutions to realize the 0BB technology. It has the advantages of high equipment compatibility, strong adhesion, and good heat resistance, and has achieved rapid industrialization progress.
Correspondingly, UV-curable adhesive materials adapted to the 0BB technology are one of the future investment directions.
By transferring the front electrode of the cell to the back, BC cells effectively reduce shielding and reflection, thereby improving the photoelectric conversion efficiency. As a platform technology, BC technology can be combined with TOPCon to form TBC cells and with HJT to form HBC technology. Therefore, it is also regarded as a major development direction of silicon-based PV. Due to the more intensive arrangement of electrodes on the back of the cell, to ensure insulation between grid lines of different polarities and avoid short circuits, it is necessary to introduce a protective adhesive material with excellent high-temperature resistance, aging resistance, and electrical insulation performance before the ribbon soldering process.
Correspondingly, high-temperature insulating adhesive materials adapted to the BC technology are one of the future investment directions.
As the third-generation solar cell, perovskite cells are regarded as a disruptive innovative star technology and have made brilliant progress in recent years. Perovskite cells use perovskite-type organic-metal halide semiconductors as light-absorbing materials, and have the advantages of high conversion efficiency, short preparation process, and large cost reduction space. Currently, perovskite cells are still in the early stage of industrialization, but there is a consensus on their huge development potential.
Correspondingly, additives, new packaging materials, and other materials adapted to perovskite cell technology are also among the future investment directions.
The above only lists some new material investment opportunities brought about by numerous PV innovative technologies. More technologies and investment directions are expected to be discussed jointly with industry experts and colleagues in the investment community in the future.
Source: Tong Jun, Investment Department II
Review: Xue Yao
Release: You Yi
