Research Of AZO Thin Films For Amorphous Thin Film Solar Cells

In situ sputtered AZO thin film attracted much attention because of the many variety applications like flat panel displays and thin film solar cells owing to its good electrical, optical and piezoelectric properties. Additionally, quasi-crystal AZO thin film providing a different shape and higher surface area might exhibit some interesting properties unattainable by other nanostructures, which is supposed to be very attractive for optoelectronic devices especially for solar cells and flat panel displays.Quasi-crystal aluminum-doped zinc oxide (AZO) films were prepared by in situ radio frequency (RF) magnetron sputtering (sputtering without annealing) on glass substrates. The influence of deposition parameters on the optoelectronic and structural properties of the in situ deposited quasi-crystal AZO films was investigated in order to compare resulting samples. The quasi-crystal AZO thin films have excellent crystallization improved with increase of the RF power and substrate temperature, with an extremely preferential c-axis orientation exhibit sharp and narrow XRD pattern similar to that of single-crystal. Field emission scanning electron microscopy (FESEM) images show that quasi-crystal AZO thin films have uniform grains and the grain size increase with the increase of RF power and substrate temperature. Craters of irregular size with the columnar structure are observed in the quasi-crystal AZO thin films at a lower substrate temperature while many spherical shaped grains appeared at a higher substrate temperature.The average optical transmittance of all the quasi-crystal AZO films was over 85% in the 400-800nm wavelength range. The resistivity of 4.176×10^-4Ωcm with the grain size of 76.4891nm was obtained in the quasi-crystal AZO thin film deposited at 300℃, under sputtering power of 140W.On the other hands, the structural, electrical and optical properties of the AZO thin films deposited on different substrates were investigated. We observed that substrates have an influence on properties of the AZO thin films. And flexible substrate especially the PI was also a suitable substrate to prepare high quality AZO thin film. And the film deposited on glass showed larger grain size, lower average roughness and resistivity. However, the AZO thin film deposited on PI and stainless steel substrates also showed highly preferential c-axis orientation with good crystallinty and low resistivity, 6.336×10^-4Ωcm and 1.252×10^-3Ωcm respectively. The average optical transmittance of the AZO thin films deposited on glass and PI substrates in the visible light range (400-800nm) are both around 85%. The good transparency-conducting property and the room-temperature deposition on PI substrate enable the AZO thin film to be suitably used in flexible optoelectronic devices such as thin film solar cells.