Bipolar conductivity in amorphous Cu-Al-O thin films prepared by r.f. magnetron sputtering

Bipolar electronic behavior has been demonstrated in amorphous Cu-Al-O thin films prepared on soda-lime glass substrate via radio frequency (r.f.) magnetron sputtering deposition technique. The tunable majority charge carrier type is as a result of the intentional adjustment of the percentage chemical composition of the material. Signs of Hall coefficients from Hall effect measurement and slopes of Mott-Schottky plots obtained for the films indicate the majority charge carrier type of each films. Negative Hall coefficient and a positive Mott-Schottky slope were obtained for the Al-rich film showing its n-type nature. Positive Hall coefficient and negative Mott-Schottky slope were obtained for the Cu-rich film showing its p-type nature. X-Ray Photoelectron Spectroscopy (XPS) was used to explain the variation in charge carrier type as a result of the adjustments made to the percentage chemical composition of the film. The I-V curves obtaine from simple devices fabricated show that the homojunction formed from the two films exhibit rectifying and photovoltaic properties. The rectifying behavior was studied between a bias of 1 V to +1 V. In addition, a V-OC of 0.33 V, a J(SC) of 8.00 mA/cm(2), an FF of 0.30 and a PCE of 0.79% were obtained from the photovoltaic device fabricated.

Automated summary

Bipolar electronic behavior was demonstrated in amorphous Cu-Al-O thin films, showing n-type and p-type properties with adjustable majority charge carrier type. X-Ray Photoelectron Spectroscopy (XPS) was used to explain the variation in charge carrier type. The homojunction formed from the two films exhibited rectifying and photovoltaic properties.