Increasing wafer size became a low hanging fruit for module makers to increase PV panel power output. This important trend influences another key physical attribute of the wafer – the wafer thickness. The rule of thumb in the industry is—reducing wafer thickness lowers manufacturing costs. For every 10 µm reduction in wafer thickness, the cost can be reduced by 3%, whereas for every 1% reduction in utilization rate of ingot cross sectional area, which happens when moving from pseudo square to full square, the cost of a silicon wafer increases by about 0.3%. Therefore from a cost reduction perspective, reducing thickness is more beneficial.
When it comes to wafer price, there is a lot of movement – and in recent months it generally quickly went down (with a recent slight uptick due to a sudden silicon shortage). LONGi's price list from July, 24 2020 included its two main products – G1 and M6 –, which are at 2.62 CNY and 2.53 CNY per piece, respectively. This is a difference of about 3%, while the area difference between these two wafer formats is about 9%. While many other considerations come into play when setting a product price, a major price reduction took place in April 2020 when the specs for thickness were reduced from 180 µm to 175 µm. The price difference was about 12%. From April 2020 onwards, LONGi has replaced M2 through G1 as a main product.
Wafer thickness not only influences cost but also the wafer size. According to LONGi, the largest monocrystalline wafer supplier, both G1 and M6 wafers are typically supplied with 175 µm thickness, which is expected to decrease further to 160 µm in the coming years. A few cell manufacturers are already considered to be thinning down their products to 170 µm. As for 182 mm wafers, the thickness is between 170 to 175 µm, while for the 210 mm format, cell producers currently prefer 180 µm thickness, according to LONGi.
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