Rationale for the Atmospheric Processing Platform
The photovoltaics (PV) industry has been increasingly interested in lower-cost, high-throughput atmospheric approaches to processing PV devices. Over the last five years, the National Renewable Energy Laboratory (NREL) has developed a suite of technologies suitable to non-vacuum direct-write processing. This suite includes the following:
- Ink-based contacts for solar cells
- Ink-based precursors to copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe) materials
- Solution-processible transparent conducting oxides (TCOs)
- Rapid thermal processing (RTP)
- Laser-based materials processing, including scribing, recrystallization, and phase formation
- Solution-based organic solar cells.
The combining of these technologies provides an overall enabling technology for new thin silicon wafer cells and thin-film compound semiconductor solar cells by
- Eliminating the need for conventional vacuum systems
- Being adaptable to novel topologies
- Providing non-contact approaches to processing.
We currently have extensive industry interest in the contact and thin-film PV areas for silicon, CIGS, and organic photovoltaics (OPV). Additional interest focuses on writing the active and encapsulating layers for CIGS and for OPV/Graetzel cells. Vacuum processes are both expensive and energy intensive. Therefore, this unique platform will be a model for potential manufacturing processes, immediately relevant to industry applications.
A key ability is to write the precursors to cell materials and process them into high-quality electronic materials. But also key is being able to chemically modify complex (or nanostructured) surfaces to enhance interfacial and mechanical properties. For this reason, we developed the Atmospheric Processing platform that includes a robotic 3-dimensional inkjet system, large-area spray system, and large-area laser and rapid thermal processing. The atmosphere can be controlled throughout processing, and in-situ diagnostic capabilities will allow researchers to determine key compositional and structural properties both during and after processing.
This integrated cluster tool has the flexibility to allow us to explore near-term contact metallizations, as well as next-generation thin-film and OPV processing technologies. Grids can be deposited as a non-contact process, as opposed to the typical screen-printing process. The solution deposition stages are universal and can be equipped with future solution deposition methods.