Photovoltaic Properties in Al-doped ZnO/non-doped Zn_(1-x)Mg_xO/Cu_2O Heterojunction Solar Cells

摘要

The influence of Mg content (Mg/(Mg+Zn) atomic ratio) on the obtainable photovoltaic properties in Al-doped ZnO (AZO)/non-doped Zn_(1-x)Mg_xO/Cu_2O heterojunction solar cells using p-type Cu_2O sheets prepared by thermally oxidizing Cu sheets was investigated, n-type Zn_(1-x)Mg_xO thin films were prepared with various Mg contents on non-intentionally heated Cu_2O sheets using a pulsed laser deposition. It was found that the obtained open circuit voltage increased gradually as the Mg content was increased up to approximately 0.18. The optimal Mg content in the n-Zn_(1-x)MgxO thin-film layer that would be suitable for achieving the highest efficiency was determined to be approximately 0.09. The obtained short circuit current density, fill factor and conversion efficiency increased gradually as the O_2 gas pressure during the depositions was increased, reaching maximum values at a pressure of approximately 1 Pa, and then their values decreased as the pressure was increased further. In contrast, the open circuit voltage increased monotonically from 0.62 to 0.85 V as the O_2 gas pressure was increased from vacuum (below 4×10~(-4) Pa) to 1.6 Pa. The highest efficiency of 4.31%, measured under AM1.5G (100 mW/cm~2) solar illumination, was obtained in an AZO/Zn_(0.91)Mg_(0.09)O/Cu_2O heterojunction solar cell fabricated with an n-Zn_(0.91)Mg_(0.09)O thin-film layer prepared with a thickness of 50 run at an O_2 gas pressure of 0.9 Pa.