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Title: Near-field transport imaging applied to photovoltaic materials

We developed and applied a new analytical technique - near-field transport imaging (NF-TI or simply TI) - to photovoltaic materials. Charge-carrier transport is an important factor in solar cell performance, and TI is an innovative approach that integrates a scanning electron microscope with a near-field scanning optical microscope, providing the possibility to study luminescence associated with recombination and transport with high spatial resolution. In this paper, we describe in detail the technical barriers we had to overcome to develop the technique for routine application and the data-fitting procedure used to calculate minority-carrier diffusion length values. The diffusion length measured by TI agrees well with the results calculated by time-resolved photoluminescence on well-controlled gallium arsenide (GaAs) thin-film samples. We report for the first time on measurements on thin-film cadmium telluride using this technique, including the determination of effective carrier diffusion length, as well as the first near-field imaging of the effect of a single localized defect on carrier transport and recombination in a GaAs heterostructure. Furthermore, by changing the scanning setup, we were able to demonstrate near-field cathodoluminescence (CL), and correlated the results with standard CL measurements. In conclusion, the TI technique shows great potential for mapping transport properties in solarmore » cell materials with high spatial resolution.« less
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0038-092X
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Solar Energy
Additional Journal Information:
Journal Volume: 153; Journal Issue: C; Journal ID: ISSN 0038-092X
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
14 SOLAR ENERGY; transport imaging; near-field; photovoltaic materials; high resolution
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1413791