CIGS Module Manufacturing Process

1. Back Contact (Molybdenum-coated):

A layer of 0.5 μm Molybdenum will be deposited onto the glass substrate as the back contact. The next step is to laser scribe dozens of metal electrodes, isolated from each other, on the Molybdenum back contact. Each electrode is a CIGS cell.

Soda lime glass, a low cost material, is used as the substrate. Sodium  goes through Molybdenum and into CIGS thin films to enhance the crystallization.

Molybdenum creates Ohmic contacts with CIGS and reduces current drawn. It is also highly reflective, able to reflect the incident light not fully absorbed into the absorption layer.

2. CIGS (absorption layer and buffer layer deposition sputtering):

A layer of 2μm P-type Cu (In x,Ga 1-x)Se2 is then coated on Molybdenum in a vacuum process. A layer of 0.05μm N-type buffer layer is deposited to form a P-N interface. A layer of ZnO is then coated as an insulation layer, to cover up the micro pores that may possibly result in electricity leakage and to enhance yield rates. The next step is to mechanical scribing.

The focus of this highly-technical process is to precisely control the  composition of all elements, consistence of temperature in thermal processing and evenness of CIGS absorption layer.

3. Front Contacts:

A layer of 0.5μm TCO (Transparent Conductive Oxide) is deposited as top electrodes. CIGS cells are completed with mechanical scribing and electrode wire connecting.

TCO should be highly conductive, highly reliable under different temperatures and toxin-free. To ensure light can be absorbed by the CIGS layer, the bandgap must be greater than the absorption layer and the transmittance should be at least 80%.

4. Module Assembly:

EVA (Ethylene Vinyl Acetate) and low-iron and tempered front glass are used to laminate CIGS cells already connected. Junction boxes are then installed to the finish modules.

The encapsulation process should avoid bubbles, breakage of substrates or incomplete lamination. Therefore, the access rate, heating speed and temperature evenness of laminators are critical to production yields.

EVA pieces together cells and glass. Durable and lasting, highly transparent and unlikely to contract, EVA can maximize the effectiveness of solar modules.

Junction boxes connect the electricity generated by different modules so that they are linked as a power system.