Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6534813 | Solar Energy Materials and Solar Cells | 2016 | 9 Pages |
Abstract
We investigated the relationship between the electrical properties (of the n-oxide semiconductor layer and the p-Cu2O sheet) and the obtainable photovoltaic properties of Al-doped ZnO (AZO)/n-oxide/p-Cu2O heterojunction solar cells that were fabricated using either p-type non-doped Cu2O or Na-doped Cu2O (Cu2O:Na) sheets (prepared by thermally oxidizing a Cu sheet) functioning as the active layer as well as the substrate. We fabricated some heterojunction solar cells using p-Cu2O (non-doped) sheets and n-ZnO thin films with various electron concentrations (N) in the range of 1017â1020Â cmâ3; non-doped and Al- or Cu-doped ZnO thin films were deposited under various O2 or O3 gas atmosphere pressures using a pulsed laser deposition (PLD) method. The obtained photovoltaic properties exhibited a tendency to increase as N was increased from 1017 to about 3Ã1019Â cmâ3; the values remained at these maximum levels as N was increased to about 8Ã1019Â cmâ3, and then they decreased as N was increased further. With an N on the order of 1020Â cmâ3, the reduction of photovoltaic properties was attributed to an increase in the discontinuity of the conduction band at the interface between the n-ZnO and p-Cu2O layers. In addition, we found that the hole concentration (P) in Cu2O:Na sheets (i.e., Cu2O sheets postannealed with various Na compounds) could be controlled in the range of 1014â1019Â cmâ3 by varying the annealing temperature and duration. As another example, the obtained photovoltaic properties in heterojunction solar cells that were fabricated by depositing n-(Ga0.975Al0.025)2O3 thin films on p-Cu2O:Na sheets by PLD remained constant as P was increased to approximately 1Ã1016Â cmâ3, and then they decreased significantly as P was increased further. The reduction of the obtained photovoltaic properties in heterojunction solar cells fabricated using Cu2O:Na sheets with a P above about 1.4Ã1016Â cmâ3 was attributed mainly to decreases of both the depletion layer width and the diffusion length.
Related Topics
Physical Sciences and Engineering
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Authors
Tadatsugu Minami, Toshihiro Miyata, Yuki Nishi,