1. Technical Difficulties:

10 or 11 steps in the PERC process, such as two lasers, one phosphorus expansion, and double-sided coating;

TOPCon adds silicon dioxide and polysilicon plating process, and boron expansion is required in the front, but there is no laser opening, and there is a wet method;

In fact, HJT only starts from cleaning, double-sided plating of microcrystalline silicon or amorphous silicon, then ITO, and then silk screen sintering. It used to be very simple, only 4 steps, but now silicon wafers still need gettering. It used to be a low-temperature process. into 8 steps.

In fact, the first major difficulty of TOPCon is boron expansion, and the second is LPCVD. Single-side plating and back-winding plating are more serious, and the yield rate is not high.

This problem is basically solved after double-sided expansion, but there are still many problems in LPCVD. The tube wall is plated very quickly. 150nm things are made of 10 furnaces of 1.5um, and the tube wall is quickly plated on the tube wall. The tube wall needs to be cleaned frequently, but the low-pressure process of The LPCVD needs to be laminated requires thick quartz tubes, and needs to be cleaned at the same time, which is a relatively big problem.

Now double casing is used, the outside is laminated, and the inside is coated with a layer of film. It is often taken out for cleaning. Although this is better, it takes some procedures. The so-called operating rate will be affected because maintenance is required.

The actual expansion of the boron itself is a difficult thing. The process steps are relatively long, resulting in relatively large yield loss, and there are some potential problems that may cause yield and production line fluctuations, diffusion burn-through and silver paste burn-through polysilicon film, resulting in passivation damage, and high-temperature processes that cause silicon wafers damage;

One of the difficulties of HJT is that PECVD maintains purification, which is required to be close to the semiconductor process, and the purity requirements are stricter than before TOPCon diffusion. After HJT2.0 and 3.0, because the hydrogen dilution rate increases, the deposition rate needs to be accelerated, and high frequency is introduced, which will lead to uniformity. sex decline.

In addition, there is also the issue of cost, how to reduce the amount of silver paste, and further improve the stability of the battery.

2. Cost difficulty:

Topcon also has pain points, one is the relatively low yield rate, and the other is CTM. The low yield rate increases the cost, and the CTM is relatively low/and the actual component power is significantly different. It is also relatively difficult to improve efficiency, and there is not much room for improvement in the future, because the frequency of equipment maintenance is relatively high; The cost difficulty of HJT is that the slurry consumption is relatively large. One is how to reduce the quantity and how to reduce the price. In addition, the CTM is relatively low. Crystallite preparation requirements are also involved, affecting cost and technology.

3. Crafting process:

Many people asked me to list the cost split. In fact, I don’t think the cost split is very meaningful. You can see that the cost reduction depends on the logic, that is, what logic is used to reduce the cost. Compare these three processes, such as comparing how high the temperature of these three is. PERC has 3 high-temperature processes, one for phosphorus expansion at 850°C, two for coating at 400-450°C, and sintering at 800°C. TOPCon high-temperature processes include boron expansion at 1100-1300°C, phosphorus expansion at 850°C, LPCVD at 700-800°C, two coatings at 450°C, and sintering at 800°C. There are many high-temperature processes, high heat load, high energy consumption, and cost.

It cannot be seen from the investment in materials and equipment, but in fact, from the perspective of electricity bills, it is at least higher than PERC. If HJT does not absorb impurities, it is actually 200°C, PE at 200°C, sintering at 200°C, and PVD at 170°C. So it is very low temperature, and the low temperature time is not long, because the coating time is very short, and it is often coated with a thickness of 2nm, 3nm, and 10nm.

However, the leaching time is relatively long, leaching a carrier board for 8 minutes from the beginning to the end. The amount of a carrier plate is less than that of a tubular PECVD, and the diffusion of tubular PECVD is 2400°C or 1200°C, while a carrier plate 12*12=144 travels faster but the amount is also small.

This is somewhat comparable, in short, the temperature is relatively low. But if fast phosphorus gettering is done, the process can reach 1000°C, but the duration is short, only 1min, and the entire heat load is much lower than TOPCon.

Let’s look at the wet process again: PERC is 3 times, TOPCon is 5 times, HJT used to have only one time of texturing without absorbing impurities, and only one piece of equipment, which is very simple. If there is dirt pick up, wash/remove the damage before the getter picks up, there is velvet at the back, and the wet process is very short.

The vacuum process of PERC includes phosphorus expansion and two PECVDs, both of which are also vacuum, but the vacuum degree is relatively low, and a rod pump is enough.

The vacuum degree of TOPCon is relatively high, and phosphorus expansion, boron expansion, LPCVD and PECVD are performed twice each time. The vacuum degree is not high, and 5 times of vacuum rod pump are enough.

There are two HJT processes, one is PECVD and the other is PVD. PVD requires a relatively high degree of vacuum and uses a molecular pump, so this will consume more energy in terms of vacuum requirements.

The entire process depends on the current cost and the future cost reduction process, and the various energy consumption and losses caused by the simple process will be much lower.