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Evaluation of Polycrystalline Silicon for Solar Cells by Small p-n Diode Array

Published online by Cambridge University Press:  26 February 2011

Satoshi Tanaka
Affiliation:
ce66037@isc.meiji.ac.jp, Meiji University, school of science and technology, 7-35-7, Shin-machi, Ome-shi, Tokyo, 198-0051, Japan
Keita Imai
Affiliation:
ee31060@isc.meiji.ac.jp, Meiji University, School of science and technology, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan
Atsushi Ogura
Affiliation:
a_ogura@isc.meiji.ac.jp, Meiji University, School of science and technology, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan
Yoshio Ohshita
Affiliation:
ohshita@toyota-ti.ac.jp, Toyota Technological Institute, 2-12-1 Hisakata, Tenpaku, Nagoya,, Aichi, 468-8511, Japan
Koji Arafune
Affiliation:
ara@toyota-ti.ac.jp, Toyota Technological Institute, 2-12-1 Hisakata, Tenpaku, Nagoya,, Aichi, 468-8511, Japan
Hideaki Kawai
Affiliation:
sd02018@toyota-ti.ac.jp, Toyota Technological Institute, 2-12-1 Hisakata, Tenpaku, Nagoya,, Aichi, 468-8511, Japan
Futoshi Kusuoka
Affiliation:
sd02019@toyota-ti.ac.jp, Toyota Technological Institute, 2-12-1 Hisakata, Tenpaku, Nagoya,, Aichi, 468-8511, Japan
Michio Tajima
Affiliation:
tajima@isas.jaxa.jp, The Institute of Space and Astronautical Science (ISAS)/ Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
Masaaki Inoue
Affiliation:
m_inoue@isas.jaxa.jp, Meiji University, School of science and technology, 1-1-1 Higashimita, Tama-ku, Kawasaki, Kanagawa, 214-8571, Japan
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Abstract

A small p-n diode array was fabricated on a polycrystalline Si substrate and the electrical characteristics were measured for each small diode to evaluate the distribution of energy conversion efficiency in the substrate. The crystal qualities in conjunction with the electrical characteristics were also evaluated. We found large variations in measuring the current-voltage (I-V) characteristics of the p-n diode. We also observed variations in quality even in diodes without any grain boundaries at the p-n junction. Therefore, we evaluated crystalline quality using various techniques to compare the diode characteristics. We found clear evidence in photo-luminescence (PL) mapping, where grains, including degraded diodes, were darker in the mapping, implying lower PL intensities than the others. The PL spectra obtained from the “dark grains” included D-lines indicating the existence of dislocations. We could conclude that the electrical characteristics of p-n diodes were not only affected by grain boundaries but also by crystalline defects evaluation such as dislocations. We observed a Secco-etched surface for crystalline defects evaluation using an optical microscope. The origins of etch pits were also determined by transmission electron microscope (TEM) and three different types of defects were confirmed.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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References

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