Studies Of Microstructures And Photoelectric Properties Of Azo Transparent Conductive Films

The effects of proceeding techniques on the photoelectric properties of AZO transparent conductive thin films prepared by RF sputtering method have been studied. The influence of the thickness of the film, the temperature of the substrate, the sputtering power on the photoelectric properties of ZnO or AZO thin films prepared by RF Sputtering and sol-gel methods have been investigated. The photoelectric properties of p-Si-n-ZnO heterojunction prepared by RF Sputtering have been tested, and the effects of the AZO transparent conductive thin films on the photoelectric properties of the Ag/AZO/n-Si-p-Si/Ag solar cell have been discussed. The main experimental results of this work are listed as following:(1) For multi-layer ZnO films deposited on the surfaces of p(100) Si substrate by the sol-gel method, charachered as TK series, with the increase of thickness of the ZnO film, the C-axis orientation of the ZnO grain gets better, however it becomes worse as the thickness of the ZnO film thicker than0.8μm. The grain size and the resitivity of the ZnO film increase with the thickness of the films. The results of PL spectrum measurements of the ZnO films indicate that there are Ulraviolet emission peak and green-blue emission band in the PL spectrum of the ZnO film.(2) For ZnO films deposited on the glass substrate with different temperatures by the RF sputtering method, charachered as TG series, with the increase of temperature of the glass substrate, the C-axis orientation of the ZnO grain gets better first and then it becomes worse, and it gets the best at the temperature of150℃of the glass substrate. The energy gap of the ZnO films prepared are3.275eV(100℃),3.287eV(50℃) and3.240eV(250℃), respectively. The light transmittance in visible region of the TG series are higher than80%.(3) The FE-SEM images for the ZnO and AZO films indicate that the surfaces of the ZnO films are uniform and the qualities of the films are perfect.(4) ZnO films doped with small amount of Al3+, charactered as AZO films, are transparent; however, with the increase of the content of Al3+in the ZnO films, the light transmittance of the films decrease, the ZnO films become black. The energy gap of the AZO film is wider than that of the ZnO film, and the resitivity of AZO film is much lower than that of the ZnO film.(5) For AZO films prepared by the RF Sputtering method under the different sputtering power, charachered as AZP series, with the increase of the sputtering power, the C-axis orientation of the AZO films get better. When the sputtering power lower than95W, with the increase of the sputtering power, the grain size and the concentration of the carrier of the AZO film increase, while the resitivity and the energy gap of the AZO film decrease. As the sputtering power is125W, the resitivity and the energy gap of the AZO film increase, the concentration of the carrier of the AZO film decrease. The light transmittances in visible region of the AZO films are higher than89%. The energy gap of the AZO films prepared by the RF Sputtering method under the different sputtering power are4.00eV(25W),3.975eV(50W),3.960eV(75W),3.925eV(95W), and4.05eV(125W), respectively.(6) For AZO films deposited on the glass substrate with different temperatures by the RF Sputtering method, charachered as AZT series, with the increase of temperature of the glass substrate, the AZT film obviously prefer to grow on the orientation of (002). This can be also confirmed by the results of XRD. The resitivity of the AZO film decrease first and then increase with the increase of the temperature of the glass substrate. As the temperature of the glass substrate higher than200℃, the resitivity of the AZO increase, while the light transmittance in visible region of the AZO films decrease.(7) For the p-Si-n-ZnO heterojunction prepared by the RF Sputtering method, the ZnO films obviously prefer to grow on the orientation of (002). The results of PL spectrum measurements of the ZnO films indicate that there are ultraviolet emission peak at380nm (about2.70eV) and green-blue emission band started from550nm. By means of the measurement of I-V curve of the Al/p-Si-n-ZnO/Ag solar cell, the parameters of the solar cell can be obtained as following:the open-circuit voltage Voc=0.56V, the short-circuit current JSc=28.1mA/cm2, the fill factor FF=30.4%, the transfer efficiency η=4.76%.(8) By means of the measurement of I-V curve of the Ag/AZO/n-Si-p-Si/Ag solar cell prepared by the RF Sputtering method, the parameters of the solar cell can be obtained as following:the open-circuit voltage Voc=0.57V, the short-circuit current Jsc=43.7mA/cm2, the fill factor FF=52.3%and the transfer efficiency η=13.02%. The experimental results indicate that the AZO film has a well contact with Si-based thin film solar cells, and the ITO films are expected to be replaced by AZO films.