Multiscale Modeling and Control of Thin Film Solar Cell Manufacturing for Improved Light Trapping and Solar Power Conversion
Photovoltaic (solar) cells are an important source of sustainable energy. Currently, their limited conversion efficiency limits their wide applicability. Thin-film silicon solar cells are the most developed and widely used solar cells. Research on optical and electrical modeling of thin-film silicon solar cells indicates that the scattering properties of the thin film surfaces/interfaces are directly related to their light trapping processes and thus their conversion efficiency. The scattering properties of the interfaces are influenced by the surface morphology, in particular, the root-mean-square (RMS) roughness and RMS slope. The aim here is to improve the efficiency of thin-film solar cells by controlling the manufacturing process via simultaneous regulation of the thin film surface RMS slope and roughness at spatial length scales corresponding to the visible light wavelength range. Computational multiscale modeling and real-time model-based control of the thin film solar cell manufacturing process to optimize light trapping and overall conversion has the potential to lead to transformative advances in solar cell technology.
Intellectual Merit
The objective of the proposed research is to develop a systematic and computationally tractable multiscale modeling and control framework for real-time control of thin film solar cell manufacturing which leads to thin film surface morphology that optimizes light trapping and overall conversion of solar power. This project will devise methods for the construction of reduced-order stochastic modeling approximations of the multiscale models of such systems, which are suitable for controller design and real-time implementation. These should predict the effect of controllable process variables on key film surface morphology parameters. On the basis of these reduced-order stochastic models, nonlinear and predictive control theory will be developed and used to produce practically-implementable feedback control systems that lead to the desired stability, performance (i.e., surface RMS slope and roughness values that lead to optimal light trapping thin film properties) and robustness properties in the closed-loop system. In addition, the design of monitoring systems for assessing actuator/sensor/controller abnormal behavior and controller reconfiguration strategies for dealing with abnormal events, as well as applications to thin film growth processes using multiscale models and realistic thin film light trapping specifications, will be pursued.
Broader Impact
Such real-time control of the thin film solar cell manufacturing process has the potential to lead to transformative advances in producing thin film solar cells with optimal solar power conversion efficiencies. The development of user-friendly software, short courses and workshops, the incorporation of research results into the curriculum and the writing of a new book on "Dynamics and Control of Thin Film Morphology: Surface Roughness, Slope and Porosity," are also within the project objectives. The education of high-quality doctoral students who take on leading positions in industry and the on-going interaction of the PIs with industry will be the means for transferring the results of this research into the industrial sector. The involvement of a diverse group of undergraduate and graduate students in the research through participation in the Center for Engineering Education and Diversity (CEED) at UCLA and outreach to the California State Polytechnic University in Pomona by offering summer internships to highly-qualified students will also be pursued.
