Photovoltaic properties of metal-merocyanine-TiO/sub 2/ sandwich cells

Technical Report · Wed Aug 01 04:00:00 EDT 1979

OSTI ID:5901390

Skotheim, T A

Photocurrent generation in thin films of merocyanine photosensitizing dyes sandwiched between an n-type semiconductor and a metal overlayer has been studied using photovoltaic techniques. In the system analyzed in detail TiO/sub 2/ single crystal, doped n-type, was used as the semiconductor and a semitransparent Au film as a metal overlayer. A comprehensive 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 and is strongly supported by a variety of steady state and kinetic measurements. An exciton diffusion length of 79 angstroms was determined by analyzing the short circuit action spectra using the theoretical model developed. Dark current voltage measurements revealed that the current is space-charge limited at high current densities with an electron trapping density of approximately 10/sup 17/ cm/sup -3/. Interpretation of the kinetics of rise and decay of the photocurrent suggests that the mobility of holes, the majority carrier in the merocyanine, is dependent on traps, the dominant trapping level having a depth of 0.11 eV. The decay of the photocurrent is monomolecular at short times and dominated by bimolecular recombination kinetics for long times of the order of seconds. The low fill factors 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. (WHK)

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5901390
• Report Number(s): LBL-9916
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
ANODES
CARRIER MOBILITY
CHALCOGENIDES
CHARGE CARRIERS
CRYSTALS
CURRENTS
DIFFUSION LENGTH
DIRECT ENERGY CONVERTERS
DISSOCIATION
DYES
ELECTRIC CONDUCTIVITY
ELECTRIC CONTACTS
ELECTRIC CURRENTS
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELECTRODES
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY GAP
EQUIPMENT
EXCITONS
FERMIONS
FILL FACTORS
FILMS
GOLD
HOLES
IMPURITIES
LEPTONS
MATHEMATICAL MODELS
METALS
MOBILITY
MONOCRYSTALS
N-TYPE CONDUCTORS
OPERATION
ORGANIC SOLAR CELLS
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
PHOTOANODES
PHOTOCONDUCTIVITY
PHOTOELECTRIC CELLS
PHOTOELECTROCHEMICAL CELLS
PHOTOVOLTAIC CELLS
PHOTOVOLTAIC EFFECT
PHYSICAL PROPERTIES
QUASI PARTICLES
REAGENTS
SEMICONDUCTOR MATERIALS
SENSITIZERS
SOLAR CELLS
SPACE CHARGE
TEMPERATURE DEPENDENCE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRAPPING