SMALL SIGNAL ADMITTANCE OF METAL CHLOROPHYLL a|Hg PHOTOVOLTAIC SANDWICH CELLS

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Abstract
Abstract— …The ac admittances of metal I chlorophyll a|Hg sandwich cells are shown to depend upon the chlorophyll (Chi) layer thickness, the aggregation state of the Chi, the light‐dark environment of the cells and the nature of the metal. The results suggest the presence of different but not independent charge transport processes in these cells. One process gives rise to a broad dispersion in the frequency dependent capacitance and conductance. This process is observed in all cells and is most readily ascribed to a hopping or tunneling of charge carriers across potential energy barriers. Another mechanism which is detected only with crystalline Chi and only with certain metal substrates is ascribed to interfacial polarization. A model circuit incorporating these interpretations yield calculated admittance data which approximate those measured experimentally.