Photocharge transport and recombination measurements in amorphous silicon films and solar cells by photoconductive frequency mixing: Annual subcontract report, 20 April 1998--19 April 1999

Technical Report · Mon Feb 28 04:00:00 EST 2000

DOI:https://doi.org/10.2172/754628· OSTI ID:754628

Braunstein, R; Kattwinkel, A; Liebe, J; Sun, G

In the present phase of the program, the transport parameters of a number of amorphous semiconductors prepared by a number of techniques were determined by the photoconductive frequency mixing technique. This technique enabled the authors to determine the drift mobility, md, and the photomixing lifetime, t. The technique is based on the idea of heterodyne detection for photoconductors. When two similarly polarized monochromatic optical beams of slightly different frequencies are incident upon a photoconductor, the generation rate of electron-hole pairs will produce a photocurrent, when a dc-bias is applied, which will contain components resulting from the square of the sum of the individual incident fields. Consequently, a photocurrent will be produced, which will consist of a direct current and a microwave current corresponding to the beat frequency. These two currents allow a separate determination of the drift mobility and the photomixing lifetime of the photogenerated carriers. In the present work, the longitudinal modes of a He-Ne laser were employed to generate a beat frequency of 252 MHz; all the measurements were performed at this frequency for the data indicated in the accompanying figures. The following topics were explored: Measurements of the charge transport parameters of homogeneous a-SiGe:H alloys produced by NREL employing the hot-wire technique; The change in the charge transport parameters in the transition from hydrogenated amorphous silicon to microcrystalline silicon for material produced by NREL and MVSystems; The improvement in instrumentation of the photomixing measurements; Measurements of the hydrostatic dependency of the transport parameters of amorphous silicon; and Preliminary photomixing measurements on p-i-n devices.

• Research Organization: National Renewable Energy Lab., Golden, CO (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC36-99GO10337
• OSTI ID: 754628
• Report Number(s): NREL/SR-520-27931
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
AMORPHOUS SILICON FILMS
BEAT FREQUENCY
CARRIER LIFETIME
CARRIER MOBILITY
GERMANIUM ALLOYS
HETERODYNE DETECTION
HOLE MOBILITY
HYDROGENATED AMORPHOUS SILICON
MEASURING METHODS
MICROCRYSTALLINE SILICON
PHOTOCHARGE TRANSPORT
PHOTOCONDUCTIVE FREQUENCY MIXING
PHOTOCONDUCTIVITY
PHOTOCURRENTS
PHOTOVOLTAICS
RECOMBINATION
RECOMBINATION MEASUREMENTS
SILICON ALLOYS
SILICON SOLAR CELLS
SOLAR CELLS