Kofi W. Adu

Assistant Professor of Physics 
Penn State Altoona

158 LRC

3000 Ivyside Park
Altoona, PA 16601
Office: (814) 940-3335

Lab: (814) 949-5666

Fax: (814) 949-5011  

Dr. Adu is experimental condensed matter physicist with expertise in engineering advanced nanomaterials, their application in new technologies and the nanoscale physics that stem from quantum confinement phenomena in these advanced nanostructures.

Education


Ph.D., Physics, Pennsylvania State University, University Park, PA, May 2004.  Dissertation Title: "Synthesis and Raman Scattering Studies of novel semiconductor nanostructures: Si, Ge and GaAs Twinning Superlattice nanowires."

B.Sc., Physics, University of Cape Coast, Cape Coast, Ghana, December 1994. Thesis Title: "Effect of ionization of impurity centers by electric field on the conductivity of superlattice."

Recent Publications

Publications

Curriculum Vitae

CV

Collaborators

Other Links

Materials Research Institute

Department of Physics UP

Web of Science

American Physical Society

Materials Research Society

APPLICATIONS

Conductive Wires

Approximately 10% of total electric energy consumed in US is lost to Joule heating. New technologies are being proposed to develop and improve the efficiency and reliability of the energy delivery systems. Dr. Aduís research focuses on using nanoengineering techniques to develop composites that are lightweight with superior thermal and electrical conductivity, high tensile strength and modulus of elasticity, tailorable coefficient of thermal expansion and specific heat capacity to address the challenges to improve the efficiency and reliability of our energy delivery system.


Thermoelectrics

Thermoelectric (TE) process provides an alternative source of harvesting energy for power generation without moving parts or production of environmental deleterious waste, and thus will play an important role in our current challenges to develop alternative energy technologies to address our dependence on fossil fuels. It is the only viable choice to harvest the waste heat energy (70% of total energy) from automobiles and factories into electrical energy. The high electrical conductivity and low thermal conductivity characteristics of nanostructures make them potential candidates for TE energy harvesting devices. Compositional tuning and different phonon scattering mechanisms: interface scattering, impurity scattering, surface scattering, defect scattering and grain boundary scattering, are being explored to decrease the lattice contribution to the thermal conductivity whilst maintaining high electrical conductivity. Different exotic nanowires (superlattice, core shell and anti-dots) and nanotubes are explored to manipulate the phonon states in the nanostructures to decrease the lattice contribution to the thermal conductivity. For example, a multi-shell nanowire which is acoustically engineered such that the acoustic impedance of the inner shell is greater than the successive shells is expected to exhibit ballistic electron transport at room temperature while simultaneously hindering thermal transport along the wire.


Photovoltaics

Solar energy represents one of the most abundant and yet least harvested sources of renewable energy. In recent years, tremendous progress has been made in developing nanoarchitectured photovoltaics that can be mass deployed. Of particular interest to cost-effective solar cells is to use novel nanostructures and materials processing techniques to develop acceptable efficiencies. Current attainable efficiencies of existing solar cell technologies range from 3.0% to 32% of which multijuction devices ~ 11%-32%, silicon cells ~ 9%-25%, group III-V cells ~18%-25%, thin film chalcogenide ~ 16%-19%, amorphous/nanocrystalline Si ~ 9%-10%, photochemical (dye sensitized) ~ 6% 10% and organic polymer ~ 3%. The objective here is to develop cost-effective nanotubes and nanowires based solar cells with high efficiency. One approach is developing solid state nanowire array solar cell in which each wire has multiple p-n junctions in the radial direction (radial superlattice). For example, a vapor-liquid-solid growth mechanism can be used to synthesize alternate shells of CdS (n-doped) and CdTe (p-doped) nanowires. This novel approach has many advantages over existing solar cells.


Electrochemical Energy Systems

Our current energy dependence on fossil fuels is having great impact on the world economy and the global ecology system. Electrochemical energy production systems are under serious consideration as an alternative energy sources. To mitigate some of the challenges in developing economically viable and environmentally friendly electrochemical energy systems, the research exploits the unique properties (high surface area, high aspect ratio and enhanced kinetics, high electrical conductivity, quantum size effect etc.) of nanostructures to develop free standing binderless macro-sized objects as electrodes in batteries, fuel cells and electrochemical capacitors.


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