During the cell production process, the thermal diffusion process often affects many factors in the performance of TOPCon solar cells, resulting in changes in cell performance. In order to scientifically evaluate the impact of the thermal diffusion process on the performance of TOPCon solar cells and understand whether the sheet resistance/resistivity after diffusion meets industrial standards, scientific testing must be carried out with sophisticated testing instruments. Millennial Solar has produced the Built-in Four-Point Probe Tester, which can be placed in the production line in conjunction with production, and can achieve scientific measurement and zero fragmentation rate during the battery testing process, thus helping photovoltaic cell manufacturers produce high-quality quality TOPCon solar cells!

Thermal Diffusion and Its Impact on TOPCon Performance Factors

Thermal diffusion process is an important step in the preparation process of TOPCon solar cells. It is mainly used to form a doped area on the surface of the silicon wafer to achieve the formation of P-N junction and selective collection of carriers. There are two main types of thermal diffusion processes: substitutional diffusion and interstitial diffusion. Substitutional diffusion means that impurity atoms replace the positions of silicon atoms to form a doped region; interstitial diffusion means that impurity atoms fill the gaps in the silicon lattice to form a doped region.

After performing the thermal diffusion process on TOPCon solar cells, photovoltaic cell manufacturers usually use testing equipment to scientifically test the TOPCon solar cells to understand the resistivity/sheet resistance and other performance parameters of the cells after thermal diffusion. For this purpose, Millennial Solar produces Built-in Four-Point Probe Tester. This equipment can be perfectly connected to the industrial production process, and can ensure zero fragmentation rate while using fully automatic 5-point and 9-point scanning measurements, so that the subsequent production of photovoltaic cell manufacturers will not be affected, thereby achieving true non-destructive testing!

Impact on TOPCon interface passivation effect

The thermal diffusion process will affect the interface state density on the silicon wafer surface, thereby affecting the interface passivation effect. The lower the interface state density, the better the interface passivation effect, the less carrier recombination, and the higher the open circuit voltage. Generally speaking, substitutional diffusion is more conducive to reducing the density of interface states than interstitial diffusion, because substitutional diffusion will reduce lattice distortion and vacancy defects. Therefore, in TOPCon solar cells, better interface passivation effect can be obtained by using the substitution diffusion process.

Impact on TOPCon Carrier Selective Collection

The thermal diffusion process affects the carrier selective collection ability of the silicon wafer surface, thereby affecting the fill factor and short-circuit current. The stronger the carrier selective collection ability, the higher the fill factor and short-circuit current will be. In the thermal diffusion process, photovoltaic cell manufacturers usually use interstitial diffusion for preparation, because interstitial diffusion is easier to achieve process stability and controllability than substitutional diffusion. The relationship between reaction rate and doping concentration and temperature of interstitial diffusion is simpler and linear. Therefore, in TOPCon solar cells, higher process stability and controllability can be obtained by using interstitial diffusion.

Impact on TOPCon process stability and controllability

Thermal diffusion process will be affected by many factors such as temperature, time, pressure, atmosphere, etc., thus affecting the stability and controllability of the process. The higher the process stability and controllability, the more uniform and reliable the photovoltaic cell performance will be. When using two diffusion types for thermal diffusion processes, it is important to understand that interstitial diffusion is easier to achieve process stability and controllability than substitutional diffusion, because the reaction rate and doping concentration of interstitial diffusion are related to temperature m ore simple and linear.

Built-in Four-Point Probe Tester

 E-mail: market@millennialsolar.cn

FPP230 Auto is a Built-in Four-Point Probe Tester specially designed for photovoltaic process monitoring. It can quickly and automatically scan the sample to obtain the sheet resistance distribution information at different positions of the sample. The measurement size can be customized according to the size of the customer's sample.

●Measuring sheet resistance in the range of 1μΩ~100MΩ

●Able to match automation equipment and traceable at any time

●Perfectly connected with the automated production process of the production line

●Provide good electrical contact while ensuring 0 fragmentation rate

●The number of measurement points can be customized according to customer needs

Thermal diffusion process has significant application value in the production of TOPCon solar cells. It can effectively improve the photoelectric conversion rate and performance of TOPCon solar cells. However, if you want to further understand its performance parameters, it must be tested through scientific and efficient testing equipment. The Built-in Four-Point Probe Tester produced by Millennial Solar can be perfectly connected with the thermal diffusion process in the production line, thereby helping TOPCon solar cells greatly reduce inspection time and increase production line production rate in mass production!