There has been a renaissance of interest in exploring highly efficient thermoelectric materials as a possible route to address the worldwide energy generation, utilization, and management. This review describes the recent advances in designing high-performance bulk thermoelectric materials. We begin with the fundamental stratagem of achieving the greatest thermoelectric figure of merit ZT of a given material by carrier concentration engineering, including Fermi level regulation and optimum carrier density stabilization. We proceed to discuss ways of maximizing ZT at a constant doping level, such as increase of band degeneracy (crystal structure symmetry, band convergence), enhancement of band effective mass (resonant levels, band flattening), improvement of carrier mobility (modulation doping, texturing), and decrease of lattice thermal conductivity (synergistic alloying, second-phase nanostructuring, mesostructuring, and all-length-scale hierarchical architectures). We then highlight the decoupling of th...

Rationally Designing High-Performance Bulk Thermoelectric Materials

Copper sulfides and copper selenides have recently been reported as new and promising low-cost and environmentally friendly thermoelectric materials. Here, it is shown that these materials have actually been studied for more than 190 years and the absence of commercial thermoelectric modules based on them stems from some major intrinsic issues related to these chalcogenides. Further development of these semiconductors will require addressing and solving these problems before large scale utilization can be considered.

Are Binary Copper Sulfides/Selenides Really New and Promising Thermoelectric Materials?

A solar cell is disclosed with V-grooves which are series connected, but electrically isolated, indirect bandgap solar cells which are responsive to different light frequencies on both sides of a semi-insulating optically transparent substrate. The device has a very high conversion efficiency of approximately 40% and high open-circuit voltage and low series resistance. An exemplary structure in accordance with this disclosure has a series of silicon V-groove cells on one side and another series of GaAlAs V-groove cells on the other side. The cells are of generally trapezoidal cross-section. The difference between the characteristics of the Si cell and the GaAlAs cell is matched by control of the number of V-grooves.

Heterojunction V-groove multijunction solar cell

Nanostructured binary copper chalcogenides (NBCCs) have been the subject of extensive research as promising candidates in energy-related and biological applications due to their advantageous properties, environmental compatibility, and abundance. The remarkable properties of these materials is born out of the variable stoichiometry between the copper and chalcogens, as well as the structural versatility, with zero-dimension to three-dimension structures, which consequently improves their electrical, optical, and catalytic properties. Here, the research history and development process of the binary copper chalcogenides are introduced. Typical synthesis strategies for NBCCs vary according to structure dimensionality and specific energy-related and biological applications dependent on the structure and stoichiometry are summarized. The future development of designed nanostructures and tuned stoichiometry in NBCCs for further high-performance applications are outlined.

Nanostructured binary copper chalcogenides: synthesis strategies and common applications.

Collection efficiency and spectral response calculations for semiconductor heterojunction solar cells

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Heterojunction solar cell calculations

A theoretical evaluation of the maximum attainable solar conversion efficiencies of p-n and n-p heterodiodes is presented. The calculations are made for some of the theoretically efficient and feasible heterojunctions of IV and III-V group semiconductors. In these calculations, the Anderson diffusion model is used and carrier concentrations of the two semiconductors are so chosen that photo-carriers generated do not have to surmount any junction barrier. The calculated efficiencies are compared with the reported experimental values and with the conventional Si photovoltaic cell.

Efficiency calculations of heterojunction solar energy converters

Diffusion of Copper in CdS Crystal from Cu2S Layer

Efficiency calculations for some p‐n and n‐p heterojunctions

The photovoltaic effect in Cu2s-CdS heterojunction has been the subject of study by a large number of investigators. Proper heat treatment of the junction plays crucial role in optimizing the performance of the heterojunction. In this paper, after a brief review of the work on Cu2S-CdS heterojunctions, the profile of copper in CdS as a function of heat treatment will be discussed. The diffusion of copper from Cu2S into CdS has been studied at various temperatures, by radioactive tracer methods. This has a bearing on the spectral response of the Cu2S-CdS cells as a function of heat treatment.

Some physical investigations on photovoltaic effects in Cu2S-CdS heterojunctions

Single crystals of Indium Selenide are prepared by vapour growth technique as it is difficult to prepare large single crystals by vertical Bridgman technique. The effect of stochiometric changes an...

A. K. Sreedhar

Papers

Efficiency calculations of heterojunction solar energy converters

Diffusion of Copper in CdS Crystal from Cu2S Layer

Efficiency calculations for some p‐n and n‐p heterojunctions

Some physical investigations on photovoltaic effects in Cu2S-CdS heterojunctions

Preparation and electrical properties of InSe