Battery technologies such as TOPCon and HJT continue to move from the laboratory to the industrial chain

1. The background of the event

A recent meeting pointed out that on the basis of the previous support, 50 billion yuan of renewable energy subsidies will be allocated to the central power generation enterprises. The issuance of this subsidy is a positive signal for the development of renewable energy in my country, which will increase the enthusiasm of domestic new energy installations, and the wind power photovoltaic industry chain is expected to benefit. Let's talk about the specific situation of the photovoltaic cell industry in detail.

Second, understand photovoltaic cells

Photovoltaic cell is an optoelectronic semiconductor sheet that uses sunlight to generate electricity directly. As long as it is illuminated by light that meets certain illumination conditions, it can instantly output voltage and generate current when there is a loop.

According to different semiconductor materials, solar cells can be divided into crystalline silicon solar cells and thin film solar cells. Crystalline silicon cells can be divided into monocrystalline silicon cells and polycrystalline silicon cells, of which monocrystalline silicon cells are further divided into P-type cells and N-type cells. At present, the most widely used monocrystalline PERC cells are P-type monocrystalline silicon cells, while new solar cell technologies such as TOPCon, heterojunction, and IBC mainly refer to N-type monocrystalline silicon cells.

Third, subdivide the track

1.TOPCon battery

TOPCon battery technology, namely the tunneling oxide layer passivation contact technology, its battery structure is an N-type silicon substrate battery, a layer of ultra-thin silicon oxide is prepared on the back of the battery, and then a thin layer of doped silicon is deposited. A passivation contact structure is formed, which effectively reduces surface recombination and metal contact recombination, improves the open circuit voltage and short circuit current of the battery, and improves the battery efficiency.

1) LPCVD is the mainstream process currently produced by TOPCon

At present, TOPCon cells have 4 different industrialized processes, namely: LPCVD to prepare polysilicon film combined with traditional full diffusion process; LPCVD to prepare polysilicon film combined with boron expansion and ion implantation phosphorus process; PECVD to prepare polysilicon film and in-situ doping process; PVD prepares polysilicon film and in-situ doping process. Among them, LPCVD technology is mature and has achieved mass production, and equipment localization is perfect, but winding plating and slow film forming speed are still the main problems of the current process.

The full name of LPCVD technology route is low-pressure chemical vapor deposition method. The advantages of this technology are mature technology, high integration, good film formation quality, large equipment capacity, and simple and easy control; but it is difficult to have slow coating speed, low film formation rate, and secondary Doping, wrapping, serious deposition of quartz parts, etc. LPCVD technology is the most widely accepted and the only technology that has been commercialized on a large scale.

2) Manufacturers accelerate TOPCon production capacity planning and advance the industrialization process. In the past two years, domestic enterprises have basically reserved space for TOPCon transformation for new PERC production lines for subsequent upgrades. The PERC production capacity of many first-tier manufacturers has gradually stopped, and the current expansion plans have also shifted to the construction of N-type technology production lines. Entering the second quarter, the TOPCon production capacity of many manufacturers including Jinko began to be released, and it is expected to enjoy the technology premium.

2. HJT battery

HJT cells are made of crystalline silicon (c Si ) and amorphous silicon (αSi ) thin films, combining the dual advantages of crystalline silicon solar cells and thin film technology, because the thin film has the characteristics of strong light absorption and excellent passivation performance. HJT has been developed for 47 years. With the iteration of technology and the improvement of conversion efficiency, HJT battery has entered the stage of domestic commercialization.

The advantages of HJT cells are that the process flow is short and the conversion efficiency is high. The HJT battery process mainly includes 4 links, which is far less than PERC (10) and TOPCON (12-13); in addition, the conversion efficiency of HJT superimposed IBC and perovskite may be increased to more than 30% in the future.

The cost reduction route of HJT is clear, and the cost of HJT in 22 years is expected to be lower than PERC. The cost of HJT battery is 0.18 yuan per watt higher than that of PERC, and 94% of the cost increase is in non-silicon cost. In the future, HJT cost reduction mainly depends on silicon consumption reduction, silver paste cost reduction, target localization, and equipment cost reduction.

3. IBC battery

IBC refers to the interdigitated back contact battery technology, and the contact electrodes of the P/N junction, the substrate and the emitter are made on the back of the battery in an interdigitated shape. IBC cells have high conversion efficiency and are more beautiful in appearance, especially suitable for photovoltaic building integration, and have good commercialization prospects. Although the advantages of IBC cells are outstanding, the process of IBC cells is complicated, and semiconductor technologies such as masks and photolithography are used many times, and the cost is almost twice that of conventional cells.

Due to the good compatibility of the IBC battery structure, three major process routes have been gradually formed: 1) the classic IBC battery process represented by SunPower; 2) the POLO-IBC (TBC) battery process represented by ISFH; 3) the Kaneka battery process The representative HBC cell process (IBC-SHJ). According to the results of the Kaneka experiment in 2017, the current conversion efficiency of IBC-SHJ (HJT) cells can reach up to 26.7%, which is higher than the experimental efficiencies of TOPCon and HJT cells.

IBC belongs to the reserve technology route, and the R&D trial production layout has been launched. At present, the IBC/HBC battery manufacturing process is complex, the technical threshold is high, and the manufacturing cost is high, which belongs to the technical route in the research and development reserve. The most mature mass production companies of IBC technology in the world are SunPower and LG.