N-type solar cell technology development analysis

In 2022, N-type cell technology came out of the laboratory and opened the first year of mass production, with a greater increase in solar cell efficiency. Last November, LONGi Green Energy's independently developed silicon heterojunction cell conversion efficiency reached 26.81%, setting the world's highest record for silicon-based solar cell efficiency. n-type cells are expected to become the next generation of PV technology leader and gradually replace P-type cells.

P-type cells mainly refer to BSF cells and PERC cells. before 2014-2015, PV cell technology was mainly BSF, whether monocrystalline or polycrystalline cells, the backside was passivated with aluminum backfield. after 2015, PERC cells developed. the backside of PERC cells is not only passivated with aluminum backfield, but also mainly passivated with alumina plus silicon nitride, effectively avoiding the previous Some technical defects. With the advantages of monocrystalline in conversion efficiency and production cost, PERC cells became the most effective technology to achieve rapid reduction in system power cost. In the following two years, the whole market gradually shifted to PERC technology. By 2022, the proportion of PERC cell products in the global market exceeds 90%.
At present, PERC cells are not so far behind, but it is predicted that in about three years at most, it will be difficult to compete with the more efficient N-type cells.

In July 2022, Trina Solar’s self-developed G12 high-efficiency PERC cell reached a maximum efficiency of 24.5%, setting a new world record. And 24.5% is already the limit of P-type cell efficiency.
Compared to P-type wafers, the carrier life of N-type wafers is at least an order of magnitude higher, why? Because N-type silicon wafers are doped with mainly “phosphorus elements”, so no boron-oxygen atom pairs are formed in the material (i.e., the main cause of photogenic attenuation in P-type cells), making the initial light-induced attenuation of N-type cells and modules almost zero. This is the fundamental difference between N-type cells and P-type cells, and because of this, the open-circuit voltage and short-circuit current of N-type cells are greatly improved, resulting in higher cell conversion efficiency.

N-type cells have many advantages, including high conversion efficiency, high bifacial rate, low temperature coefficient, no light decay, good weak light effect, and longer carrier life.
N-type cell technology can be subdivided into heterojunction (HJT), TOPCon, IBC and other technology types. Currently, PV cell manufacturers mostly choose TOPCon or HJT to pursue mass production.
The theoretical efficiency of N-type TOPCon cells can reach 28.7%, and the theoretical efficiency of heterojunction cells can reach 27.5%.

TOPCon technology is a technology based on the “N-type cell” process, and continues to develop the “tunneling through oxide layer passivation contact”.

According to theoretical calculation, the current TOPCon mainstream battery mass production efficiency is about 23.7-23.8%, some battery manufacturers announced that they have achieved 24.0%+, including: many companies such as Zhonglai shares have achieved laboratory efficiency of 25% or more, and the future prospects are bright.

TOPCon and PERC are both high-temperature processes, and can maximize the retention and use of existing traditional P-type battery equipment process, the two cell technology and line equipment compatibility is high. TOPCon can be upgraded from the PERC line, without the need for new lines. If only upgrading on the original PERC process, it only needs to increase the investment amount of €7M-14M/GW, the marginal investment cost is better than other N-type technology routes. the production line of PERC technology is the mainstream application of P-type cells, then under the pressure of depreciation accrual of large-scale PERC production line equipment assets, continue to upgrade and transform the equipment into TOPCon production line, is favorable to reduce the sinking risk.
In the future, with the decline of non-silicon cost and further improvement of yield and efficiency, TOPCon will quickly narrow the cost gap with PERC and become the mainstream product of the new generation.

Because of the large existing capacity of PERC cells, the new PERC capacity in 2019 will basically reserve the TOPCon interface for subsequent transformation and upgrade. And the current PERC capacity of many large first-tier factories has gradually stopped capacity.

At present, the main companies involved in TOPCON technology are: Longi, Jolywood, JinkoSolar, Trina Solar, Orient Sunrise, etc., which are mostly vertically integrated companies. Among them, Jolywood is one of the earliest TOPCon layout companies, and the average conversion efficiency of the company’s TOPCon cell mass production batch is 24.2%, with some products reaching 24.5%.

According to PVInfoLink and Tiburon New Energy, the industry-wide TOPCon capacity is expected to exceed 40GW by the end of 2022, and is expected to reach about 80GW by the end of 2023.

The HJT process is very different from the TOPCon mentioned above, which was upgraded from the “P-cell” production line. Therefore, many manufacturers choose to continue to upgrade and transform TOPCON in order to save costs. So, what is the advantage of HJT?

The HJT cell process, mainly consists of only 4 links, fleece making, amorphous silicon deposition, TCO deposition, and screen printing. The process flow is much lower than the 10 for PERC and 12-13 for TOPCON. This makes the new manufacturers who want to enter the market nowadays, prefer HJT technology. This gives the new manufacturers the possibility to compete with the established manufacturers.

In the laboratory, the conversion efficiency of TOPCon is around 24%, while the mass production efficiency of N-type cells is generally already above 24%. HJT cells can use doped nanocrystalline silicon and doped microcrystalline silicon on the front and back surfaces respectively, and the conversion efficiency may be increased to more than 30% by stacking IBC and chalcogenide in the future.

According to the relevant data: HJT cells decay 1-2% in the first year, and 0.25% per year thereafter, which is much lower than the decay of PERC cells (2% in the first year, and 0.45% per year thereafter), and therefore the life-cycle power generation per watt of HJT cells is about 1.9%-2.9% higher than that of double-sided PERC cells.

HJT and PERC process route is completely different, can not be extended, only new production line; and HJT is not compatible with mainstream PERC production equipment, so already use PERC process, and then transition HJT, will bring higher conversion costs to enterprises. Therefore, HJT technology is more friendly to companies below the second or third line or new technology industries, without the historical baggage of capacity.

According to incomplete statistics, the capacity and expansion plans disclosed by 24 companies, such as China Resources Power, CNBM, Runyang, Huasheng New Energy and Akcome Technology, the future HJT capacity planning has reached 112GW.

Along with the market mainstream cell-PERC cell efficiency improvement began to slow down, and the industrialization of N-type wafer-based heterojunction cells gradually mature, the focus of PV cell industry development is quietly changing. Industry experts believe that compared to other technology routes, HJT cell technology has a better conversion rate and cost reduction space, but also more suitable for combining with IBC, calcium titanium ore and other technologies, this technology is known in the industry as the next generation of commercial PV production of important candidate technology.

As A PV Module Manufacturer With 14 Years Of Expertise, Maysun Solar Is Researching And Developing N-Type PV Modules And Is Ready To Work With You To Help The Energy Transition. Contact Us To Open The Door To Green Energy.