What is Process & Equipment (P&E)?

Process refers to how photovoltaic modules are fabricated, including the kind of materials and fabrication techniques used, and the manufacturing flow. Equipment refers to the manufacturing infrastructure used to produce these modules.

A CIGS-based solar cell consists of multiple thin film materials that are layered on glass or on flexible webs in the following order: Molybdenum (positive terminal), CIGS (sunlight absorber), Cadmium Sulfide (transparent window), and Zinc Oxide (negative terminal or front contact).

Process & EquipmentCIGS photovoltaic cell structure. Image by Alfred Hicks/NRELFabrication techniques to produce layered films range from ones that disperse material physically in gaseous form (referred to as physical vapor deposition) to ones that deposit materials by chemical reactions (referred to as chemical vapor deposition). Sputtering, thermal evaporation, chemical bath deposition, and atomic layer deposition are examples of thin film deposition techniques that are commonly used for CIGS solar cells. Solar cell films are encapsulated within glass or a transparent polymer and are deployed into sunlight as air tight modules.

P&E Challenges in CIGS Manufacturing

Standards for CIGS photovoltaic panel manufacturing equipment currently do not exist in the industry. CIGS module companies have unique manufacturing processes and equipment sets, which makes any standardization difficult. Examples of some of the P&E challenges in the CIGS industry include:

  • The unit processes in a CIGS manufacturing flow can be either in an in-line or in a batch-type configuration. This creates challenges in transporting substrates between processes that do not have the same throughput.
  • Most of the thin-film deposition processes are vacuum-based. If a non-vacuum unit process step is present in a series of vacuum processes, then a tool cannot be designed with all the unit thin film process in a single chamber. Additional substrate handling capability will be needed for loading-unloading different tools.
  • The CIGS process itself is complicated by the four-element chemistry. Maintaining compositional and thickness uniformity of the thin-film across the large sized glass or the flexible web is a design challenge.

The above issues create challenges for equipment design and increase tool cost. Additionally, these issues affect electrical performance of the photovoltaic panel and the overall manufacturing throughput.

PVMC Addresses P&E challenges

Through a flexible engagement model, PVMC enables industrial participants to collaborate in consortial activity or proprietary research programs. In both models, PVMC uses its internal capabilities to address challenges facing the industry. CIGS P&E infrastructure available at PVMC includes a 100kW pilot line (glass & flex-based) and a 10 MW roll-to-roll manufacturing line (flex-based) that produces photovoltaic panels. Participating companies establish their product prototypes at PVMC and leverage PVMC’s infrastructure to demonstrate product performance in an end-to end photovoltaic panel manufacturing setting. For example, a sputtering company installs its in-line tool next to PVMC’s batch-type tool and compares the performance of photovoltaic panels made with both tools; or a target manufacturer compares photovoltaic performance using its materials with standard materials that are a part of the PVMC line. The access to PVMC’s infrastructure allows participating companies to continuously improve their products.

PV equipment

PVMC also leverages knowledge from industry experts to support P&E improvement activities. These experts develop long term technology improvement roadmaps for the CIGS module companies that are available to participating members. These roadmaps serve as guidelines for the upstream supply chain to improve their products. PVMC takes into account both the roadmaps as well as the project selection inputs from the participating companies to address P&E challenges in the industry, helping improve the overall quality products that are supplied to the CIGS industry.