The Robert Resnick Lecture Series

The thermodynamic power conversion efficiency limit for silicon solar cells is close to 33%, while commercially available cells have efficiencies in the 17-20% range.  The world record for silicon solar cells has inched upward from 25% to 26.7%, in the past twenty years, using cell thicknesses ranging from 450 microns to 165 microns.  Photonic crystal architectures enable broadband light absorption beyond the longstanding Lambertian limit and allow silicon to absorb sunlight nearly as well as a direct-bandgap semiconductor.  When combined with state-of-the-art electronics, a technological paradigm shift appears imminent.  In this lecture, I describe how wave-interference-based solar light-trapping in realistic photonic crystals can break longstanding barriers, enabling flexible, thin-film, silicon to achieve an unprecedented, single-junction, power conversion of 31% [1, 2].

1.  "Towards 30% Power Conversion Efficiency in Thin-Silicon Photonic-Crystal Solar Cells,"   S. Bhattacharya, I. Baydoun, Mi Lin and Sajeev John, Physical Review Applied, 11, 014005 (2019)

2. “Beyond 30% conversion efficiency in silicon solar cells” S. Bhattacharya and Sajeev John (to be published)

Watch Professor Sajeev John's lecture on Photonic Crystal Light Trapping

This talk reviews some of the applications of topology and topological defects in phase transitions in two-dimensional systems for which Kosterlitz and Thouless split half the 2016 Physics Nobel Prize. The theoretical predictions and experimental verification in two dimensional superfluids, superconductors and crystals will be reviewed because they provide very convincing quantitative agreement with topological defect theories.

Thermoelectrics are semiconductor materials that are used to convert heat flow to electricity, or to convert electricity to heat flow. They are the basis of solid state refrigeration, and solid state power generation. It has become a large technical industry with many new products and applications. In this lecture, I review the science of thermoelectric, and give examples of thermoelectric materials and thermoelectric-based products. I also discuss the nature of the Seebeck coefficient in a typical semiconductor such as silicon.