Photovoltaic properties of Au--merocyanine--TiO/sub 2/ sandwich cells. II. Properties of illuminated cells and effects of doping with electron acceptors

Journal Article · Wed Dec 15 04:00:00 EST 1982 · J. Chem. Phys.; (United States)

OSTI ID:6613025

Skotheim, T; Yang, J; Otvos, J; Klein, M P

Photocurrent generation in thin films of a merocyanine photosensitizing dye sandwiched between a TiO/sub 2/ single crystal doped n type and an Au overlayer has been studied using photovoltaic techniques. A theoretical model was developed to explain the observed photovoltaic properties. The model assumes that the principal route for the formation of charge carriers is via singlet excitons diffusing to the merocyanine--TiO/sub 2/ interface followed by dissociation of the excitons into electron--hole pairs, the electrons being injected into the TiO/sub 2/ conduction band and the holes into the merocyanine. The model also incorporates field dependence of the quantum efficiency for charge generation. An exciton diffusion length of 79 A was determined by analyzing the short circuit action spectra using the theoretical model developed. The low fill factor of 0.35 for these cells was attributed to the field dependence of the quantum efficiency and the high series resistance of the undoped merocyanine films. Doping the merocyanine films with iodine was found to increase both the dark conductivity and the steady state photoconductivity. The carrier generation in iodine doped films is shown to result from a bulk process, possibly involving collisions between singlet excitons and acceptor--hole complexes resulting in activation out of the bound states formed by the charge-transfer complex. The quenching of excitons in the immediate vicinity of the metal surface was studied by monitoring the photoconductive response of a 200 A merocyanine film with varying thickness of perylene sandwiched between the metal and the merocyanine. Perylene was shown to be able to transport the photoexcited holes from the merocyanine to the Au electrode. The quantum efficiency for photocarrier production increased to a maximum of 21% for a 750 A thick perylene layer.

• Research Organization: Laboratory of Chemical Biodynamics, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720
• OSTI ID: 6613025
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 77:12; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
AROMATICS
CHALCOGENIDES
CONDENSED AROMATICS
CRYSTAL DOPING
CYANINE DYES
DIRECT ENERGY CONVERTERS
DYES
EFFICIENCY
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EXCITONS
FILMS
GOLD
MATHEMATICAL MODELS
METALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PERYLENE
PHOTOCONDUCTIVITY
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
QUANTUM EFFICIENCY
QUASI PARTICLES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS