Hisao Morooka

INTERFACE STATES IN ZNO VARISTOR WITH MN, CO, AND CU IMPURITIES

The interface states in ZnO with impurities of transition-metals, Mn, Co, and Cu, were investigated by the DLTS (deep-level transient spectroscopy) measurements in ZnO/PrCoO x /ZnO junctions as model systems of ZnO ceramic varistors and by the SCF-Xα-SW molecular orbital calculations using simplified cluster models. The DLTS signals, correlated to the doping of Mn and Co, are obtained with ZnO/PrCo x /ZnO junctions. The signals correspond to the interface states due to the transition-metal doping. Xα calculations indicate that the interface states attributed to the doping of transition-metals, Mn, Co, and Cu, in ZnO are created between the valence band and the conduction band, which consist of transition-metals 3 d character. The impurities of transition-metals affect interface states as well as the adsorbed excess oxygen.

Deep-Level Transient Spectroscopy of Interface States in ZnO/PrCoOx/ZnO Thin-Film Junctions

Deep-level transient spectroscopy is successfully applied to detect interface states in ZnO/PrCoOx/ZnO thin-film junctions. The interface state is measured at 0.70 eV below the conduction-band edge. The junctions are equivalent to a model of a single grain boundary in a ceramic varistor.

Fabrication and properties of flexible a-Si:H solar cells with textured AlSi alloy electrodes

Abstract A back-reflective textured electrode was made by sputtering both pure Al and AlSi alloy materials. The electrode surface morphology and the light trapping effects related to the a-Si:H based solar cell were studied. The optical properties of the back reflective textured electrodes were examined from diffuse reflectance. The diffuse reflectance could be changed within the range 5% to 70% when the AlSi alloy material was used. The surface morphology of the textured electrodes was also changed by the use of AlSi alloy. The characteristics of the solar cell were investigated in respect of the relation between surface morphology of the textured electrode and the enhancement effect of the collection efficiency. Fine surface morphology was obtained when the AlSi alloy material was used and the short circuit current of the solar cell was increased effectively by the use of the textured electrode.