Matthew S. Branham

15.7% Efficient 10‐μm‐Thick Crystalline Silicon Solar Cells Using Periodic Nanostructures

Only ten micrometer thick crystalline silicon solar cells deliver a short-circuit current of 34.5 mA cm(-2) and power conversion efficiency of 15.7%. The record performance for a crystalline silicon solar cell of such thinness is enabled by an advanced light-trapping design incorporating a 2D inverted pyramid photonic crystal and a rear dielectric/reflector stack.

A thermodynamic framework for analyzing and improving manufacturing processes

In this paper, we present the formulation of a framework for the quantitative thermodynamic analysis of manufacturing processes and systems. Since manufacturing typically involves the input of high-quality material/energy and/or dissipation of low-quality energy/waste to manipulate a material, an approach that combines both the first and the second laws of thermodynamics is appropriate. This formulation helps emphasize that the improvement of manufacturing processes and systems is more a question of both utilizing the quantity and conserving the quality of energy than merely conserving energy. We conclude with two examples of its application, the first a comparison of metal casting technologies and the second a contrast between high-throughput CNC machining and a slower process rate grinding operation.

Deconstructing Energy Use in Microelectronics Manufacturing: An Experimental Case Study of a MEMS Fabrication Facility

Semiconductors are quite energy intensive to manufacture on the basis of energy required per mass of material processed. This analysis draws on original data from a case study of the Analog Devices Micromachined Products Division MEMS fabrication facility to examine the consequence of process rate on the energy intensity of semiconductor manufacturing. We trace the impact of process rate on energy intensity at different length scales, first presenting top-down data, then results of a bottom-up study, and concluding with individual process analyses. Interestingly, while production increased by almost a factor of 2 over the course of the study, energy demand remained virtually constant. At its most efficient, 270 kWh of electricity were required per six inch wafer in the manufacture of the MEMS devices produced at the fabrication facility. In part, the large amount of energy required per unit output is a function of the preponderance of energy used by support equipment; our data show that the facility support equipment is responsible for 58% of total energy requirements.