SOLARE - Turnkey Production Line for Crystalline Solar Cells

Introduction

SINGULUS TECHNOLOGIES is an established machine supplier with customers producing BSF, PERC and Heterojunction solar cells. SINGULUS TECHNOLOGIES is offering turnkey production lines for crystalline solar cells.

SINGULUS TECHNOLOGIES’ expertise includes vacuum thin-film coating (PECVD, sputtering, evaporation), surface engineering, wet-chemical processes and thermal processing. SINGULUS TECHNOLOGIES cooperates with cell manufacturers worldwide and develops processes, which improve the efficiency of solar cells and at the same time reduce production costs. Evolutionary improvement in cell concepts like PERC (PERL/PERT), bifacial PV systems, n-type material, IBC cell or heterojunction cells will drive the future of crystalline solar cells.

SINGULUS TECHNOLOGIES offers all the services necessary to build a turn-key solar cell production line. This service includes the planning and technical design of the production building, all supplies and additional equipment. Depending on the planned manufacturing capacity, the technical plans including the investment needs are created. SINGULUS TECHNOLOGIES offers not only the cell production line, but also the upstream ingot wafer production and solar module line with the complete accessories.

01 Wafer Stack Splitting, Loading/Inspection
Silicon solar cells are produced from raw wafers. After unloading from transport boxes, these wafers are tested to ensure that they have the right dimensions and weight and to check for any damage/cracks to the edges and surfaces. Good wafers are loaded into the system.

02 Saw Damage Etch (SDE) and Texturing
Batch-type wet benches (SILEX II) are one choice for cleaning and either alkaline texturing of mono-crystalline or acidic texturing of multi-crystalline wafers. Another option for higher capacities are inline wet chemical processing systems LINEX. In this process step any residue and saw damage is removed from the raw wafers and a light trapping structure (texture) is applied by wet chemical process. The etching and rinsing is done automatically in separate baths in an automized sequence.

03 Junction Formation
Today’s standard raw material is positively doped silicon (p-type). To generate the p-n junction, the wafers are doped with phosphorus. For this process, the substrates are loaded into silicon carbide/quartz process boats/cassettes and are inserted into a tube furnace. Inside the furnace the wafers are exposed to a phosphorus containing as (POCl3). At high temperatures of about 900 °C phosphorus atoms diffuse into the wafers. As a result a negatively doped surface layer is created.

04 Phosphorus Silicate Glass Removal/Edge Isolation
For this process step, SINGULUS TECHNOLOGIES offers the SILEX II batch and LINEX inline wet processing systems. The phosphorus silicate glass produced as a by-product of the diffusion process is removed in an acid bath. Additionally edge isolation can be realized with the LINEX inline system (PSG-EE).

05 SINGULAR – ICP-PECVD Production Platform for Passivation and Anti-reflection Coatings
The SINGULAR system provides an automation module and a coating module. The coating module consists of several customizable vacuum chambers. This high flexibility guarantees a fast and easy transfer of development concepts to industrial production. The innovative SINGULAR tool is based on static inline production, which combines the advantages of inline substrate transport and static processing. It allows the coating of complex layers, such as layer stacks of different materials e. g. AlOx/SiNy. The key feature of the tool is the ICP-PECVD technology. The inductively coupled plasma (ICP) excitation allows ideal control of film properties for various materials such as SiNx, AlOxand SiOxat high deposition rates.

06/07 Printing/Firing
To extract the electrical power from the solar cell a silver paste contact grid (busbars and fingers) is applied two times (double print) or separately (dual print) to the front surface of cell by a screen printing process. This creates the characteristic grid pattern on the front of the cell. The back of the cell also receives two silver paste contact strips plus an aluminum layer known as the back surface field. This acts on the electrons as a kind of a mirror. The contacts are burnt into the cell in a hot furnace with around 900 °C. The high temperature causes the silver paste to penetrate into the silicon, thus forming a reliable electrical contact.

08 Testing/Sorting
Tested and classified PV cells need to be sorted and placed safely into storage or transportation boxes. For this purpose the sorter takes over the cells together with their identifier from the upstream testing machine. The cells are picked up by a vacuum suction cup and moved to the respective bins which are predefined by the testing and classification unit. Standard foam boxes are used for taking up the cells. The basic machine allows sorting into 16 classes. Optionally this may be extended to 32 or 48 classes.

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