Multi-wavelength characterization of cadmium telluride solar cell: Development of Q-EBIC and NSOM measurement techniques

Gianfrancesco, Anthony Giacomo

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Multi-wavelength characterization of cadmium telluride solar cell: Development of Q-EBIC and NSOM measurement techniques

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Thin-film inorganic solar cells, such as CdTe, have demonstrated the most promise to date for a viable low-cost renewable energy resource. Their current performance, however, is far from the theoretical limit suffering from significant charge recombination losses due to grain boundaries and point defects. It is likely that the microscopic compositions of grain bulk and grain boundaries are significantly different and not optimal for the overall device performance. Good understanding of charge transport along and across the grain boundaries and other microscopic interfaces is lacking, preventing the development of reliable and predictive device models. The insufficient microscopic understanding hinders efficient characterization of photovoltaic materials and also holds back the development of process control techniques. We first show preliminary results for a novel technique, quantum-dot electron-beam induced current to characterize semiconductors in the near-field. We also propose the use of near-field optical scanning microscopy for high precision optical excitation and for local, high-resolution characterization. These imaging techniques are examined with the goal of synthesizing information obtained by both methods, of material phenomena at the relevant length scales, to other measurement methods. The most important nanoscale phenomena being the separation of compositional and electrical effects.

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