NanoPERC – Industrial processes for nanocontacted poly-Si layers for a PERC successor technology with passivating contacts

In the NanoPERC project, a successor technology to the PERC solar cell will be developed. It will feature passivating contacts based on poly-Si with an efficiency of more than 23.5% and the necessary processes and equipment for industrial mass production. The desired cell structure replaces the current efficiency limiting phosphorus emitter of the PERC cell with a rear passivating n-type poly-Si contact. The p-type Si wafer and the passivation of the second side with an AlOx/SiNy layer stack are deliberately designed close to the current production for faster market integration of the cell. The cell process can be shortened by using a one-sided deposition of poly-Si. Therefore, the poly-Si layers are deposited with the innovative sputtering coating techniques. For this purpose, a suitable sputtering process must be determined and a thermal healing process developed with which the sputtered layers are converted into polycrystalline silicon with excellent passivation properties. The aim is to produce highly doped layers in a single step with targets suitable for industrial applications. In addition, a wet-chemical process for texturing, polishing, cleaning and oxidation with ozone is being developed in a single equipment. For this purpose, different process sequences and plant engineering challenges will be investigated. Using the developed wet-chemical and deposition processes, high-quality passivated n+-type contacts will be demonstrated. In addition, the corresponding equipment concepts for industrial implementation in inline operation will be developed for these processes. Moreover, a new front metallization design is being developed for module integration. These cells will then be used to produce a module with an efficiency of 22%.