Buffer Layer for CIGS

Beneq ALD buffer layer for CIGS solar cells

One of the most promising cells today is copper-indium-gallium-diselenide (CIGS). Atomic layer deposition (ALD) can be used to improve the efficiency of CIGS solar cells by more than 1 percentage point. This is achieved by depositing a dense and conformal zinc oxysulfide Zn(O,S) buffer layer.
 

Using ALD conveniently eliminates the only liquid phase deposition step, chemical bath deposition (CBD), from the process flow, which in turn simplifies production routines and significantly reduces cost. The Thin Film System TFS 1200 from Beneq is designed for in-line or multi-module batch buffer layer deposition on CIGS. TFS 1200B off-line 4 batch module can coat 1200 × 1600 (mm) panels at a throughput of 60 panels per hour, equivalent to a total of 140 MW_p per year.

Increased cell efficiency

Beneq ALD technology enables replacing the conventional cadmium sulfide (CdS) buffer layer with one with a higher band gap energy and light transmission, thus resulting in a more than 1 percentage point increase in unit efficiency. With ALD, it is possible to adjust and optimize the oxygen/ sulfur (O/S) ratio of the film type for the CIGS panel. The intrinsic properties of ALD coatings, conformal and dense, enable enhanced blocking of pinholes in the CIGS cells.

Adapted to industrial production

ALD offers a manufacturer of CIGS solar cells the opportunity to introduce cadmium-free buffer layers, which means less of a load on the environment and less stringent in-house material safety routines. ALD is a dry coating process, which means there is no excessive water handling, no toxic effluents and no need for waste water purification. In addition, Beneq ALD equipment can be seamlessly integrated into the production line, alongside other vacuum deposition steps, resulting in negligible exposure of the substrate to atmospheric gases.

Beneq TFS 1200 Thin Film System for ALD

The Beneq TFS 1200 is an ALD processing module that is integrated into CIGS evaporation or rapid thermal processing (RTP) selenization lines. Deposition time for a 30 nm thick Zn(O,S) buffer layer is less than 5 min. ALD is more compact and less expensive than conventional CBD-CdS buffer layer processes.

More information about the TFS 1200 is available on the TFS 1200 equipment page.

More information

Download CIGS Buffer Layer brochure (pdf).