NXT Measuring Technology’s PV Cell Inline Process Quality Control Tool

Maintaining the desired cell efficiency during mass-scale production requires consistency and stringent quality control of multiple critical process steps that directly influence the end product’s performance, resulting in a high-quality and efficient PV module. For instance, irrespective of PV cell structures, like PERC, TOPCon, HJT, Tandem, or IBC, the periodic inline quality control (IPQC) of texturing and etching processes on solar wafers can ensure how well the cell can absorb light. Going further downstream process, the monitoring and controlling of coating processes of different dielectric or conductive thin film layers, such as SiNx, AlOx, SiOx, SiOxNy, TCO, ITO, and AZO, can identify and correct process instabilities to maintain uniform coatings and achieve high-performing cells. 

To fill in these critical inline process quality control stages during cell production, NXT Measuring Technology, a Germany-based high-precision spectrometric measurement tool maker, displayed its latest offerings at its stall at Intersolar Europe 2025. During a quick stop at the company’s booth, Shravan Chunduri, Head of Technology at TaiyangNews, gained brief insights into NXT’s latest inline and offline measurement tools from the CEO, Rüdiger Kubitzek.

Kubitzek says that, having more than 30 years of experience in serving different industries like solar, lithium battery, and OLED display, the company’s focus is primarily on inline metrology for process control. However, typically in the solar industry, it focuses on different types of processes in cell fabrication. 

According to the datasheet, the company has 3 major inline process control measurement tools – NXT Helios-rc (control texturing and etching processes of solar wafers), NXT Helios-tn (controlling coating processes on Si-based solar wafers), and NXT Helios-r8 (process and quality control of Poly-Si coatings on TOPCon solar wafers). During the booth exhibiting, the company showcased an offline type of NXT Helios-rc and an inline type of NXT Helios-r8 model, noted Kubitzek.  

Product Description 

NXT Helios-rc 

Addressing the need for precise process control of chemical treatment like texturing and etching to ensure high cell efficiency, the NXT Helios-rc tool can measure the total and spatial angle reflectance on the front and rear side of the treated wafers, respectively. With a spectral acquisition speed of less than 100 ms, this tool can support inline measurement, aligning with the throughput target. Alongside ensuring textured wafer surface quality, this tool can measure the color and thickness of thin layers (like anti-reflective coating on the wafer) on either the front or rear of the wafer, as stated in the company’s datasheet.  

NXT Helios-tn  

Functional coatings, like SiNx, AlOx, SiOx, SiOxNy, TCO, ITO, AZO, etc., are being increasingly used to improve the efficiency of different solar cell, attributed to better anti-reflective properties and achieving desired passivation. Thus, monitoring and measuring both material properties and coating thickness of the underlying thin film coating layer during production stages have become essential for PV cell producers. In response to this need, the NXT Helios-tn tool can measure the layer thickness, optical constants – refractive index (n), and extinction coefficient (k) across single or multiple layers, with high precision, according to the company's datasheet. Notably, this tool can measure thin-film layers produced from multiple thin-film coating routes – ALD, PECVD, LPCVD, and PVD.  

NXT Helios-r8 

This tool is particularly developed for measuring thickness and optical constants (n&k) of Poly-Si layers deposited on top of a thin tunneling oxide layer in a TOPCon cell structure. According to the company, the monitoring and controlling of the thin Poly-Si layer ensures high-quality rear-side selective passivating contact.