Preparation And Characterization Of Boron Doped Zinc Oxide Transparent Conductive Thin Films For Solar Cells

Zinc Oxide (ZnO) is a kind of newly wide band gap II-VI group compoundsemiconductor material. The similar electrical and optical properties compared to ITO,in addition to the advantages such as environmentally friendly, ease of preparation,and low cost, make the family of doped ZnO (with B, Al, Ga, In, etc.) potentiallycompetitive transparent conductive film materials. Among them, Boron-doped ZnO(ZnO:B) has high optical transmittance and good stability in the visible andnear-infrared spectral regions. As a result, light absorption in solar cell would beenhanced, and the longer warranty would be guaranteed.In this thesis, ZnO:B transparent conducting thin films deposited on glasssubstrate by pulsed magnetron sputtering were studied. And XRD, SEM, AFM,UV-Vis-NIR spectrophotometer, Hall measurement and four-probe methods wereused to characterize and analyze the structural, optical and electrical properties ofZnO:B transparent conducting thin films. The relationship between critical sputteringparameters (substrate temperature, sputtering power, sputtering pressure, sputteringtime) and the properties of thin films were investigated systematically, optimizedsputtering process for better performance of ZnO:B thin films was obtained.The main results showed that:(1) ZnO:B deposited by pulsed magnetron sputtering was hexagonal wurtzitestructure nanostructured thin film with c-axis preferential growth. The opticaltransmittance of the films was over80%in the visible spectral region, and it hadhigher transmission in the near-infrared spectral region. Moreover, sputteringprocess conditions had a significant effect on the electrical properties of thefilms.(2) Higher substrate temperature and sputtering power promoted the sputteredparticles to nucleate, crystallize and grow on the substrate, leading to improvingthe crystalline quality of the films, and the optical and electrical properties of thefilms could be enhanced at last. (3) Optimized sputtering parameters: substrate temperature was200℃, sputteringpower was100W and sputtering pressure was0.5~1Pa.(4) High quality ZnO:B thin films with c-axis preferred orientation were depositedunder the optimal sputtering process conditions. The film surface was uniform,dense and flat. It exhibited a better transparent conductive performance, theoptical transmittance was over83%(film thickness is527nm), and the electricalresistivity was as low as1.48×10-3Ω cm. It was suitable for thin film solar cellsas transparent electrode, and would be used in the field of thin film solar cellsintensively.