R. J. Schwartz

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Very high efficiency solar cells (VHESC) for portable applications that operate at greater than 55 percent efficiency in the laboratory and 50 percent in production are being created. We are integrating the optical design with the solar cell design, and have entered previously unoccupied design space that leads to a new paradigm. This project requires us to(More)
The theoretical and experimental performance of an interdigitated back contact solar cell is described. This type of cell is shown to have significant advantages over a conventional solar cell design when used at high concentration levels, namely, reduced internal series resistance, nonsaturating open-circuit voltage, and an absence of shadowing by front(More)
The use of solar concentrators can significantly reduce the cost of solar energy conversion, provided that the photovoltaic cells can be operated at high efficiencies under high illumination conditions. This paper describes the design, fabrication, and results of testing a cell with interdigitated p<sup>+</sup>and n<sup>+</sup>fingers on the unilluminated(More)
In this article we present preliminary results from a new technique for flow simulation in realistic anatomical airways. The airways are extracted by means of Level-Sets methods that accurately model the complex and varying surfaces of anatomical objects. The surfaces obtained are defined at the sub-pixel level where they intersect the Cartesian grid of the(More)
The maximum efficiency of multijunction photovoltaic systems is determined for independently connected solar cells that are optically in series. The maximum efficiency is computed as a function of solar concentration using both the Shockley-Queisser detailed balance radiative limit for the reverse saturation current density and a simple empirical expression(More)
Power loss associated with lateral current flow in solar cell emitter layers is known to cause fill-factor degradation. In this work, a unique approach to modeling the lateral current flow in solar cell emitter layers is developed using MATLAB<sup>&#x2122;</sup> and current-generation models based upon one-dimensional detailed numerical cell models. An(More)
High efficiency solar cell concentrator systems, particularly non-tracking systems, may utilize optical systems that involve lenses, secondary concentrators, dichroic mirrors and other optical components in conjunction with a variety of cells that may be optically and electrically connected in series or parallel configurations. This paper describes the(More)
In this paper, an expression for the PV system efficiency is derived that can be used in conjunction with measured device performance and detailed numerical modeling to analyze PV system performance. Such an analysis will help identify design trade-offs and also help to identify which system and cell design changes will be of greatest benefit to the(More)
Two important factors in achieving maximum power output in a multi-junction concentrator solar cell are selecting optimal sub-cell band gaps and absorber layer thicknesses. This optimization is spectrum-dependent and does not guarantee maximum yearly energy delivery, as the distribution of spectral energy varies throughout the day and year. A simple,(More)
Using embedded solar cell models in optical modeling programs has proven to be very useful for system level design optimization. These models can be used to provide quick analysis of the performance of high efficiency multijunction concentrator photovoltaic systems. They can be designed to predict the performance of the experimentally measured cells or(More)