SBIR Phase I:Large Area Real-Time Raman Imager for Layered Structures

This Small Business Innovation Research (SBIR) Phase 1 project describes a Raman imaging spectrometer based on the proprietary Volume Bragg Grating (VBG) technology. The instrument will also employ different wavelength Raman sources in order to perform the analysis of multilayer thin films solar cells. This approach is based on the dependency of the penetration depth on the laser source wavelength. The commercial thin film solar cell panels such as a-Si and CIGS [CuInGaSe], reach only ~ 60% of the conversion efficiencies demonstrated in the laboratory, mostly due to various material quality and uniformity problems. The proposed Raman instrument will be eventually used as an online process control sensor to improve the yields and quality of the solar cell thin film deposition processes. The main tasks of the Phase 1 are the design of the VBG based Raman imaging instrument and the assembly of a bench top prototype instrument. Several samples of thin film solar cell structures (a-Si and CIGS) will be analyzed with the prototype instrument. We expect to demonstrate the ability to analyze multilayer structures and thus create foundation for the design and construction of an online process control unit in Phase 2. The broader impact/commercial potential of this project is the significant advance in the conversion efficiency of commercial solar panels, based on a-Si and CIGS thin film technology. Market projections for thin film based solar panels predict sales of $6 billion in 2012. Thus, any improvement in the conversion efficiency brought by the proposed Raman process control sensor will have a huge commercial impact, amounting to perhaps hundreds of millions of dollars. While Raman spectroscopy has been used to analyze solar materials, it has not been used directly on the thin film manufacturing line as we proposed here. The on-line monitoring will yield new insights into causes of material quality and uniformity problems encountered in thin film solar panels and lead to their reduction and thus higher manufacturing yields. Higher yield will benefit the manufacturers as well as the users of solar panels produced by this technology.