Das Solar recently announced the latest progress on N-type TOPCon3.0 technology at the Solar Module Innovations Conference, organized by TaiyangNews. Based on the two technology combination of high-density laser industry-selected emitter (i-SE) and ultrathin polycrystalline silicon film on the rear (ut-polySi), Das Solar developed TOPCon3.0 high-efficiency cells and modules that are now being produced in full mass production, with an average efficiency of 25.2%, and a maximum efficiency of 25.6%.

Das Solar industrialized TOPCon cell efficiency distribution

What kind of performance metrics are TOPCon3.0 generating?

As introduced by Dr Dengyuan Song, CTO of Das Solar, the Das Solar’s TOPCon N-type technology has successfully upgraded for the three generation from the first R&D line establishment in 2019. TOPCon 3.0 is a comprehensive upgrade based on the 2.0 version, which was characterized by 16 main grids (16BB) and the higher emitter sheet resistance on the front side of the solar cell, as well as the passivation contact by SiOx/doped polycrystalline silicon on the back side. These technologies enhance the passivation effect and significantly reduces the reflection of incident light and improves the solar cell efficiency upto 24.5%.

However, the biggest challenge to further improve the efficiency over 25% is to increase the solar cell’s EQE in the shorter wavelength and the long wavelength spectrum. Due to technology accumulated over the past years, Das Solar has successfully developed the TOPCon 3.0 based on i-SE industrialization technology, which effectively reduce the recombination current on the front side, as well as the backside ut-polySi technology effectively reduces the parasitic absorption of polycrystalline silicon layer in the long wavelength, and significantly improve the utilization of the long wavelength spectrum. The perfect combination of these two technologies has improved TOCon solar cell efficiency over 25.2%.

Das Solar TOPCon cell roadmap

What is the key technologies of TOPCon3.0 ?

The key technology of i-SE is to achieve precision diffusion with a high doped concentration in a local area below the fine metal grid line, which reduces metal contact resistance. Das Solar precisely controls the laser energy field distribution and temperature field distribution on the silicon surface, and forms a highly concentrated doping zone consistent with the laser energy distribution through precision diffusion.

The ultra-thin polycrystalline Si technology (≤100m) on the rear of the cell is the deposition of thin high-quality polycrystalline silicon films. The thin polysilicon can reduce the parasitic absorption of infrared light and improve the EQE of infrared light as well as passivation contact performance. The TOPCon 3.0 deposits ultra-thin, high quality polysilicon films by low pressure chemical vaper deposition (LPCVD) , which is based on SiH4 thermal decomposition, which has the higher polysilicon quality of all polysilicon growth methods (PECVD, PVD, etc.).

TOCon3.0 key technology

DAON series modules: fully upgraded

The TOPCon 3.0 technology will continue to increase the overall performance of the module. DAON N-type products are fully upgraded in terms of reliability and power. Based on TOPCon3.0 technology, the full series of DAON N-type silicon high-efficiency modules with the highest module efficiency of 22.8% will bring high power density from a nominated area and high investment returns for large-scale ground power plants, commercial and industrial rooftops and residential users. By the end of 2023, Das Solar's N-type cell capacity and module capacity will reach respectively 30 GW. Currently, Das Solar is further developing TOPCon4.0 N-type technology to increase the conversion efficiency of TOPCon cells to over 26%.