| AVS 57th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuA |
| Session: | Advances in Surface and Interface Imaging |
| Presenter: | B.P. Gorman, Colorado School of Mines |
| Authors: | B.P. Gorman, Colorado School of Mines H.L. Guthrey, Colorado School of Mines A.G. Norman, National Renewable Energy Laboratory Y. Yan, National Renewable Energy Laboratory M. Al-Jassim, National Renewable Energy Laboratory R.P. O'Hayre, Colorado School of Mines |
| Correspondent: | Click to Email |
Fundamentally, photovoltaic and fuel cell devices rely upon interfaces for electrical power generation. However, the undesirable formation of poor quality interfaces can also serve to decrease power efficiency. In the case of photovoltaics, interfaces control the generation and extraction of photogenerated charge carriers; however, the formation of dislocations and dopant clustering can result in recombination centers, thus reducing the ability to extract charge carriers. In fuel cells, the three phase boundary between the electrode, gas, and electrolyte controls the cell power output; however, surface contamination at this interface can reduce the electrochemical reaction rate, and thus the power output of the cell. Understanding both of these interfaces at the atomic structural and chemical level allows for a greater understanding of the formation of interface degradation. In order to fully understand the atomic scale chemistry and structure of interfaces in photovoltaics and fuel cells, we have applied a combination of in-situ FIB / SEM electrical probing using EBIC and ex-situ impedance spectroscopy with high resolution analytical STEM imaging and laser pulsed atom probe tomography. These techniques have been applied to III-V based photovoltaics to gain an understanding of dopant profiling across quantum structures and tunnel junctions, and to probe the initial stages of phase separation in multicomponent epilayers. Similarly, EBIC has been used to identify dislocations and grain boundaries in polycrystalline Si photovoltaics, and to determine the atomic level chemistry and structure at these interfaces that leads to an interface acting as a recombination center. Finally, a combination of STEM and atom probe tomography have illustrated 10-17 / cm^3 changes in local Pt, C, and O chemistry and structure around Pt catalysts for use in polymer electrolyte fuel cells. In order to enable atom probe analysis on materials with widely varying field evaporation characteristics, new FIB specimen preparation techniques were required. Details on the complex experimental methods and instrumentation developed in order to enable all of these investigations are illustrated.