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Title: Field collapse due to band-tail charge in amorphous silicon solar cells

Abstract

It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain themore » decrease of FF with the increasing light intensity.« less

Authors:
;  [1];  [2]
  1. National Renewable Energy Lab., Golden, CO (United States)
  2. Syracuse Univ., NY (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
OSTI Identifier:
416141
Report Number(s):
NREL/TP-410-21091; CONF-960513-
ON: DE96007880; TRN: 96:006561-0037
DOE Contract Number:  
AC36-83CH10093
Resource Type:
Conference
Resource Relation:
Conference: 25. photovoltaic solar energy conference, Washington, DC (United States), 13-17 May 1996; Other Information: PBD: May 1996; Related Information: Is Part Of NREL preprints for the photovoltaic specialists conference of IEEE twenty-five; Gwinner, D. [ed.]; PB: 172 p.
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; SILICON SOLAR CELLS; SPACE CHARGE; FILL FACTORS; AMORPHOUS STATE; BAND THEORY; ILLUMINANCE

Citation Formats

Wang, Qi, Crandall, R S, and Schiff, E A. Field collapse due to band-tail charge in amorphous silicon solar cells. United States: N. p., 1996. Web. doi:10.1109/PVSC.1996.564326.
Wang, Qi, Crandall, R S, & Schiff, E A. Field collapse due to band-tail charge in amorphous silicon solar cells. United States. https://doi.org/10.1109/PVSC.1996.564326
Wang, Qi, Crandall, R S, and Schiff, E A. 1996. "Field collapse due to band-tail charge in amorphous silicon solar cells". United States. https://doi.org/10.1109/PVSC.1996.564326. https://www.osti.gov/servlets/purl/416141.
@article{osti_416141,
title = {Field collapse due to band-tail charge in amorphous silicon solar cells},
author = {Wang, Qi and Crandall, R S and Schiff, E A},
abstractNote = {It is common for the fill factor to decrease with increasing illumination intensity in hydrogenated amorphous silicon solar cells. This is especially critical for thicker solar cells, because the decrease is more severe than in thinner cells. Usually, the fill factor under uniformly absorbed red light changes much more than under strongly absorbed blue light. The cause of this is usually assumed to arise from space charge trapped in deep defect states. The authors model this behavior of solar cells using the Analysis of Microelectronic and Photonic Structures (AMPS) simulation program. The simulation shows that the decrease in fill factor is caused by photogenerated space charge trapped in the band-tail states rather than in defects. This charge screens the applied field, reducing the internal field. Owing to its lower drift mobility, the space charge due to holes exceeds that due to electrons and is the main cause of the field screening. The space charge in midgap states is small compared with that in the tails and can be ignored under normal solar-cell operating conditions. Experimentally, the authors measured the photocapacitance as a means to probe the collapsed field. They also explored the light intensity dependence of photocapacitance and explain the decrease of FF with the increasing light intensity.},
doi = {10.1109/PVSC.1996.564326},
url = {https://www.osti.gov/biblio/416141}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed May 01 00:00:00 EDT 1996},
month = {Wed May 01 00:00:00 EDT 1996}
}

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