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Title: Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000

Abstract

This report describes research focused on improving the individual component cells from which the multijunction devices are fabricated. The Mid-Bandgap and Metastability subteam and the Low-Bandgap subteam have the responsibility to develop appropriate materials for the respective layer of the triple-junction solar cell. To this end, it is necessary to characterize the materials that are prepared for the appropriate layer to optimize the devices and to develop an understanding of the conditions responsible for light-induced degradation so as to develop means to mitigate the degradation. Using the photomixing technique, UCLA was able to determine the mobility and lifetime separately of a number of semiconductor materials. We have established that different kinetics of degradation occur for mobility and lifetime. We have found that the drift mobility is electric-field dependent, and we developed a model for the charge transport through long-range potential fluctuations that enable a determination of the range and the depth of these fluctuations for material in the annealed and light-soaked states. UCLA has continued to provide transport parameters for the Mid-Gap, Metastability, and Low-Band teams. The materials studied were prepared by various deposition techniques. In phase II of this program, we investigated in detail the charge-transport properties by photomixingmore » of a-Si:H, {mu}c-Si:H and a-SiGe:H alloy films prepared by hot-wire chemical vapor deposition (HWCVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques, particularly under the conditions of high deposition rate and the transition from amorphous to microcrystalline state. Photomixing experiments were initiated to compare intrinsic film properties and device performance, and to study the impact of the changed contact geometry on the results of our photomixing measurements. We also attempted to employ the photomixing technique to measure the drift mobility of the transparent conducting oxide. Following our previous measurements of the transport parameters under hydrostatic pressure, we initiated the hydrostatic pressure dependence of small-angle X-ray scattering measurements to find the origin of the inelastic effect. Time-resolved photo- and thermoelectric effects (TTE) were used to simultaneously determine the thermal diffusivity, carrier lifetime, carrier mobility, and trap-level density in crystalline and amorphous Si (a-Si:H) and Si/Ge (a-Si/Ge:H) samples.« less

Authors:
; ;  [1]
  1. University of California/Los Angeles
Publication Date:
Research Org.:
National Renewable Energy Lab., Golden, CO (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
788773
Report Number(s):
NREL/SR-520-30811
TRN: AH200136%%223
DOE Contract Number:  
AC36-99GO10337
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 29 Aug 2001
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 14 SOLAR ENERGY; CARRIER LIFETIME; CARRIER MOBILITY; CHARGE TRANSPORT; CHEMICAL VAPOR DEPOSITION; FREQUENCY MIXING; PRESSURE DEPENDENCE; RECOMBINATION; SEMICONDUCTOR MATERIALS; SILICON; SOLAR CELLS; THERMAL DIFFUSIVITY; TRANSPORT; PV; TRIPLE-JUNCTION SOLAR CELL; LIGHT-INDUCED DEGRADATION; PHOTOMIXING MEASUREMENTS; CHARGE-TRANSPORT PROPERTIES; HYDROSTATIC PRESSURE; HIGH DEPOSITION RATE; HWCVD; PECVD

Citation Formats

Braunstein, R, Kathwinkel, A, and Sheng, S R. Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000. United States: N. p., 2001. Web. doi:10.2172/788773.
Braunstein, R, Kathwinkel, A, & Sheng, S R. Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000. United States. https://doi.org/10.2172/788773
Braunstein, R, Kathwinkel, A, and Sheng, S R. Wed . "Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000". United States. https://doi.org/10.2172/788773. https://www.osti.gov/servlets/purl/788773.
@article{osti_788773,
title = {Photocharge Transport and Recombination Measurements in Amorphous Silicon Films and Solar Cells by Photoconductive Frequency Mixing: Annual Subcontract Report, 20 April 1999 - 19 April 2000},
author = {Braunstein, R and Kathwinkel, A and Sheng, S R},
abstractNote = {This report describes research focused on improving the individual component cells from which the multijunction devices are fabricated. The Mid-Bandgap and Metastability subteam and the Low-Bandgap subteam have the responsibility to develop appropriate materials for the respective layer of the triple-junction solar cell. To this end, it is necessary to characterize the materials that are prepared for the appropriate layer to optimize the devices and to develop an understanding of the conditions responsible for light-induced degradation so as to develop means to mitigate the degradation. Using the photomixing technique, UCLA was able to determine the mobility and lifetime separately of a number of semiconductor materials. We have established that different kinetics of degradation occur for mobility and lifetime. We have found that the drift mobility is electric-field dependent, and we developed a model for the charge transport through long-range potential fluctuations that enable a determination of the range and the depth of these fluctuations for material in the annealed and light-soaked states. UCLA has continued to provide transport parameters for the Mid-Gap, Metastability, and Low-Band teams. The materials studied were prepared by various deposition techniques. In phase II of this program, we investigated in detail the charge-transport properties by photomixing of a-Si:H, {mu}c-Si:H and a-SiGe:H alloy films prepared by hot-wire chemical vapor deposition (HWCVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques, particularly under the conditions of high deposition rate and the transition from amorphous to microcrystalline state. Photomixing experiments were initiated to compare intrinsic film properties and device performance, and to study the impact of the changed contact geometry on the results of our photomixing measurements. We also attempted to employ the photomixing technique to measure the drift mobility of the transparent conducting oxide. Following our previous measurements of the transport parameters under hydrostatic pressure, we initiated the hydrostatic pressure dependence of small-angle X-ray scattering measurements to find the origin of the inelastic effect. Time-resolved photo- and thermoelectric effects (TTE) were used to simultaneously determine the thermal diffusivity, carrier lifetime, carrier mobility, and trap-level density in crystalline and amorphous Si (a-Si:H) and Si/Ge (a-Si/Ge:H) samples.},
doi = {10.2172/788773},
url = {https://www.osti.gov/biblio/788773}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {8}
}