Lauryn L. Baranowski

Concentrated solar thermoelectric generators

Solar thermoelectric generators (STEGs) are solid state heat engines that generate electricity from concentrated sunlight. In this paper, we develop a novel detailed balance model for STEGs and apply this model to both state-of-the-art and idealized materials. This model uses thermoelectric compatibility theory to provide analytic solutions to device efficiency in idealized materials with temperature-dependent properties. The results of this modeling allow us to predict maximum theoretical STEG efficiencies and suggest general design rules for STEGs. With todays materials, a STEG with an incident flux of 100 kW m−2 and a hot side temperature of 1000 °C could achieve 15.9% generator efficiency, making STEGs competitive with concentrated solar power plants. Future developments will depend on materials that can provide higher operating temperatures or higher material efficiency. For example, a STEG with zT = 2 at 1500 °C would have an efficiency of 30.6%.

Evaluation of photovoltaic materials within the Cu-Sn-S family

Next-generation thin film solar cell technologies require earth abundant photovoltaic absorber materials. Here we demonstrate an alternative approach to design of such materials, evaluating candidates grouped by constituent elements rather than underlying crystal structures. As an example, we evaluate thermodynamic stability, electrical transport, electronic structure, optical and defect properties of Cu-Sn-S candidates using complementary theory and experiment. We conclude that Cu2SnS3 avoids many issues associated with the properties of Cu4SnS4, Cu4Sn7S16, and other Cu-Sn-S materials. This example demonstrates how this element-specific approach quickly identifies potential problems with less promising candidates and helps focusing on the more promising solar cell absorbers.

Effective thermal conductivity in thermoelectric materials

Thermoelectric generators (TEGs) are solid state heat engines that generate electricity from a temperature gradient. Optimizing these devices for maximum power production can be difficult due to the many heat transport mechanisms occurring simultaneously within the TEG. In this paper, we develop a model for heat transport in thermoelectric materials in which an “effective thermal conductivity” (κ_eff) encompasses both the one dimensional steady-state Fourier conduction and the heat generation/consumption due to secondary thermoelectric effects. This model is especially powerful in that the value of κeff does not depend upon the operating conditions of the TEG but rather on the transport properties of the TE materials themselves. We analyze a variety of thermoelectric materials and generator designs using this concept and demonstrate that κ_(eff) predicts the heat fluxes within these devices to 5% of the exact value.

CuSbSe2 photovoltaic devices with 3% efficiency

Recent technical and commercial successes of existing thin film solar cell technologies motivates exploration of next-generation photovoltaic (PV) absorber materials. Of particular scientific interest are compounds like CuSbSe

Synthesis and optical band gaps of alloyed Si–Ge type II clathrates

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Synthesis of Group IV Clathrates for Photovoltaics

, which do not have the conventional tetrahedral semiconductor bonding. Here, we demonstrate 1.5 {\mu}m thick CuSbSe

Combinatorial Reactive Sputtering of In2S3 as an Alternative Contact Layer for Thin Film Solar Cells

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Efficient route to phase selective synthesis of type II silicon clathrates with low sodium occupancy

PV prototypes prepared at 380-410°C by a self-regulated sputtering process using the conventional substrate device architecture. The p-type CuSbSe

Development of ZnSiP

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absorber has a 1.1 eV optical absorption onset, ~