Exclusive Interview with Academician Shen Honglie, PhD Supervisor of the Asia-Pacific Academy of Materials: With Accelerated "Cost Reduction and Efficiency Enhancement", the PV Cell Industry is Poised for Takeoff
As the global concept of energy conservation gains popularity, photovoltaic (PV) cell green technology has emerged as a rising star in the industry. In recent years, China’s PV sector has achieved rapid development, with its industrial chain gradually extending to both upstream and downstream links, forming a complete PV industrial chain nationwide. Currently, the industry has entered a phase where Chinese PV enterprises lead global technological progress: since the core of the PV industry lies in converting solar energy into electricity, improving efficiency and reducing costs inevitably require technological innovation in the PV cell and module industrial chain to achieve large-scale application of quality and efficiency enhancement. Nanjing Innovation Investment Group (hereinafter referred to as "the Group") has invited Shen Honglie, Professor and PhD Supervisor of Nanjing University of Aeronautics and Astronautics, and Academician of the Asia-Pacific Academy of Materials, to discuss the prospects and outlook of PV cells.
Shen Honglie is a Professor and PhD Supervisor at Nanjing University of Aeronautics and Astronautics, and an Academician of the Asia-Pacific Academy of Materials. He has been awarded the title of "Chinese PhD Recipient Who Has Made Outstanding Contributions" and the Second Prize of the Ministry of Education’s Science and Technology Progress Award. He has led over 30 R&D projects in the fields of photovoltaics and semiconductor functional materials, including national "863" Program projects, National Natural Science Foundation projects, and major scientific and technological achievement transformation projects of Jiangsu Province. He has published more than 300 SCI-indexed papers and obtained 28 authorized invention patents.
First, could you give a general introduction to the development history of PV cells?
Solar photovoltaic cells (referred to as PV cells for short) are devices that directly convert solar energy into electricity. Crystalline silicon PV cell technology has gone through three generations:
The first-generation cell technology (before 2016) was the conventional Al-BSF (Aluminum Back Surface Field) cell, which had an aluminum film deposited on the back. The cell efficiency loss was caused by recombination at the interface between the back surface and the Al metal.
The second-generation cell technology (2017 to present) includes crystalline silicon P-type PERC (Passivated Emitter and Rear Cell) and PERC+ cells. These cells use an aluminum oxide passivation layer deposited on the back to reduce recombination, making them the most cost-effective mainstream products.
The third-generation cell technology (2021 marked the first year of its industrialization) is the N-type high-efficiency cell technology, including TOPCon (Tunnel Oxide Passivated Contact), HJT (Heterojunction with Intrinsic Thin-layer), and IBC (Interdigitated Back Contact) cells. The high-efficiency passivated contact technology adopted by these cells can reduce contact recombination between metal electrodes and the cell.
As domestic and foreign demand shifts toward high-efficiency products and the pace of "cost reduction and efficiency enhancement" accelerates, N-type cells represent the next direction of iterative development.
From the perspective of substrate type, PV cells can be divided into P-type and N-type cells. P-type cells use P-type silicon wafers (doped with boron) as raw materials, while N-type cells use N-type silicon wafers (doped with phosphorus). P-type cells mainly include BSF (conventional Al-BSF cells) and PERC cells; currently, the mainstream technologies for N-type cells are TOPCon and HJT. N-type silicon wafers have a longer minority carrier lifetime, resulting in less light-induced degradation of the manufactured solar cells and thus stronger power generation capacity.
The PV industry is currently in a high boom cycle. In which link will the main changes in the PV industry focus in the next few years?
Undoubtedly, the main changes will focus on the cell link. Other links include silicon materials, monocrystalline pulling, modules, and power stations. The future prospects of PV cell manufacturers will largely depend on their ability to master new technologies. Currently, cell technology is one of the key competitive focuses in the PV industry, and major leading PV enterprises are competing to lay out the next-generation N-type cell routes.
The current mainstream technology route in the cell link is PERC. We have also seen other technology routes such as HJT and TOPCon, and Longi has even launched HPBC. What is the substitution potential of each of these for PERC? Which technology route do you think has the most potential?
That’s exactly the case. At present, PERC is the mainstream technology in the PV market, while two new types of cells—HJT and TOPCon—are gradually emerging. I predict that within five years, the market share of these two new cell types will surpass that of PERC cells. The HPBC recently launched by Longi is actually a type of IBC cell, but it uses P-type monocrystalline silicon wafers, which have mature technology and relatively low prices. Due to the complexity of its manufacturing process, its substitution for PERC solar cells will be relatively slow. However, from the perspective of long-term development, IBC cells and various derived back-contact crystalline silicon solar cells have the greatest potential.
In your opinion, within the next 5-10 years, is it more likely that one technology route will dominate, or that multiple technology routes will coexist?
I believe that within the next 5-10 years, the market share of PERC will continue to decrease significantly from nearly half in 5 years, while the share of the two new crystalline silicon solar cells—HJT and TOPCon—will account for most of the PV market. Among them, the market share of HJT will be slightly higher than that of TOPCon, because HJT has fewer process steps, and more importantly, ultra-thin cells (less than 100 microns) manufactured using heterojunction technology can significantly reduce the production cost of HJT cells. In other words, these two will become the mainstream of the PV market.
In the competitive landscape you predicted, what type of companies do you think will capture a larger market share?
I believe that technology-based companies with original technologies will occupy a larger market share. Currently, the PV industry is facing fierce technological competition, and the days when high returns could be obtained solely through capital investment are gone forever. Over the past decade, there have been numerous PV enterprises that have achieved rapid development by mastering core technologies. For example, Shanghai Aiko Solar Energy Co., Ltd. has mastered the key technology of tubular PERC cells and took the lead in developing 210mm large-size monocrystalline silicon PERC solar cells; Suzhou Maxeon Technology Co., Ltd. has developed PECVD (Plasma-Enhanced Chemical Vapor Deposition) equipment for amorphous silicon deposition, which is used in HJT cell production; and Suzhou Saiwu Applied Technology Co., Ltd. recently officially announced the successful development of an adhesive that converts ultraviolet light into visible light, which will be widely used in HJT solar cells.
In the context of the transformation of new technology routes, what derivative investment opportunities do you think the Group should focus on?
First, attention should be paid to the R&D and manufacturing technology of PV equipment. Technology in the PV field is advancing rapidly with each passing day. Taking solar cells as an example, many new structures and processes rely on new equipment to be realized. As mentioned earlier, Suzhou Maxeon expanded and developed PECVD equipment from the semiconductor industry for HJT cell production, and has gained industry recognition. Next, a type of equipment called hot-wire CVD (HWCVD) is also worthy of attention. Compared with PECVD, it has advantages such as no warpage, lower equipment costs, and lower operating costs, and will become a strong competitor to PECVD in the future.
Second, PV auxiliary materials: such as crucibles, ribbons, junction boxes, PV glass, adhesives, low-temperature silver paste, flexible glass, and backsheets.
Third, modules: heat-dissipating modules and flexible modules.
Fourth, PV power stations: intelligent operation technology, cleaning robots, tracking brackets, etc.
Fifth, new cell technologies: IBC cells and their derivatives, as well as tandem cells.
Finally, recycling of crystalline silicon PV modules: After 2025, a large number of crystalline silicon PV modules will enter the decommissioning phase, requiring the development of recycling equipment technology and technologies for the separation and purification of high-value materials.
Thank you for Professor Shen’s sharing. The PV industry is a sunrise industry strongly supported by the state. It is believed that in the next decade, China will promote the development of the industry by greatly increasing the scale of PV installed capacity and reshape the energy system.
Source: Shen Honglie, Nanjing Innovation Investment Group
Reviewer: Xue Yao
Publisher: You Yi
