CUT-A – Cutting Edge Characterization and Technology for Germany’s PV Industry, Project Part A

Duration: April 2015 - December 2018
Contracting Authority/ Sponsors: Federal Ministry for Economic Affairs and Energy (BMWi)
Website: Project information at EnArgus (in German Language)
Project Focus:
process flow for the production of PERC solar cells
© Fraunhofer ISE
The process flow for the production of PERC solar cells is streamlined and simultaneously supports the highest solar cell efficiency and reproducibility.
bus bars on the front side metallization
© Fraunhofer ISE
There are five bus bars on the front side metallization. Solder pads for module integration can be applied on the reverse side.

The “CUT-A” project focuses on the further development of PERC solar cells made of monocrystalline and multicrystalline p-type silicon, passivated on both sides, for which the basic technology was developed in the course of various PV-TEC predecessor projects and transferred to the industry. This technology will have the largest market share in the year 2020 according to current estimates of market research institutes. It is currently being driven by Germany’s photovoltaic industry as its central short to medium-term technology. Essential aspects of the project are firstly the modernization and expansion of the PV-TEC process platform and further development of sub-processes, and secondly the development of the overall process through the regular production of PERC solar cells.

The “CUT-A” project on the basis of the Photovoltaics Technology Evaluation Center PV-TEC will offer the fast and cost-effective development of cutting edge process technology for the German PV industry. This cell structure/material combination is being elevated to a considerably higher efficiency level of 20.0% (mc-Si) or 21.5% (Cz-Si) in the course of the project. Two aspects are being pursued here in parallel: (i) ensuring the high quality of the basic processes and (ii) further development of the process to obtain a peak efficiency, previously not attained for large surface multicrystalline silicon solar cells, on equipment suitable for production. The basic technology is being continuously adapted to the peak results.

The production process and equipment used in the project meet the standards applied in industrial manufacturing. Monocrystalline and multicrystalline silicon wafers with an edge length of 156 mm are initially textured with a base or acid after saw damage etching. The homogenous emitter is formed in a tubular furnace process including in-situ oxidation. Producing a selective emitter is possible as well. This is followed by wet chemical edge isolation and the passivation of the surfaces using plasma-enhanced chemical vapor deposition (PECVD) and/or atomic layer deposition (ALD). The passivation of the reverse side is locally opened using a laser process. Screen printing is used to apply the metallization on the front and reverse sides. Contacting takes place in the continuous furnace.

Efficiencies of 21.4% (Cz-Si) and 19.6% (mc-Si) with homogenous emitters have been achieved in PV-TEC with this process flow to date. The stability and continuity of these results has been proven as well. Various wafer materials can be used. The suitability of the solar cells for module integration was also demonstrated. Thus, the PV-TEC platform is ideal for material, wafer, cell, and module manufacturers, but especially also for equipment manufacturers along the photovoltaics value chain in order to test and develop new processes or systems with this basic process.

In the sister project CUT-B , also financially supported by the Federal Ministry for Economic Affairs and Energy (BMWi), we are among other things examining the material and process-related causes for fluctuations in the efficiency of multicrystalline silicon solar cells with a passivated emitter and passivated reverse side.