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Light-Induced Conductivity Enhancement in Boron-Doped ZnO Thin Films Deposited by Low-Pressure Chemical Vapor Deposition
Y. Tawada, H. Fujiwara
LPCVD, Spectroscopic Ellipsometry, Free-Carrier Absorption, Light Soaking, Zinc Oxide (ZnO)
Thin Film Solar Cells
Subtopic: Amorphous and Microcrystalline Silicon Solar Cells
Event: 27th European Photovoltaic Solar Energy Conference and Exhibition
Session: 3BO.1.2
2137 - 2139
ISBN: 3-936338-28-0
Paper DOI: 10.4229/27thEUPVSEC2012-3BO.1.2
0,00 EUR
Document(s): paper


We have found the light-induced conductivity enhancement in ZnO layers, incorporated as front electrodes of hydrogenated-amorphous-silicon (a-Si:H)/microcrystalline-silicon (μc-Si:H) tandem solar cells. The light-induced change has been observed particularly in ZnO:B layers deposited by low-pressure chemical vapor deposition. In all the ZnO:B layers with different B concentrations, the increase in carrier concentration (5×1019 cm-3) as well as mobility (>5 cm2/Vs) under the light illumination of AM1.5G (100 mW/cm2) has been confirmed. The carrier properties of the ZnO:B layers have been characterized by spectroscopic ellipsometry (SE) using the Drude analysis. The SE results were compared with those obtained from the Hall measurements, and these results revealed that the light-induced change occurs predominantly in the ZnO intragrains, rather than the grain boundaries. The increase in the ZnO carrier concentration by the light soaking has been found to reduce the short-circuit current in the μc-Si:H bottom cell due to the increase in free carrier absorption.