| Monoclinic cupric oxide ?CuO? is native p-type semiconductors with bandgaps of 1.2-1.9 eV. A CuO p-n homojunction solar cell has a theoretical maximum conversion efficiency of 31%. They are promising semiconductor materials for solar cells because of their optical and electrical properties, as well as their abundance, nontoxicity, and low cost. Electrical properties of intrinsic CuO film is poor ?low carrier concentration and high resistivity? and it can be improved by optimizing the preparation conditions, annealing, and doping. In this dissertation, CuO and Li doped CuO films were prepared on quartz substrate by pulsed laser deposition?PLD?. Structural, optical, and electrical properties of the CuO thin films were studied. The results are: The effects of substrate temperature on the structural, electrical, and optical properties of CuO thin films were investigated. Films deposited in different substrate temperature were CuO. Increasing the substrate temperature to a moderate level ?300 ? in this study? could improve crystalline quality of the CuO films, which yielded the lowest electrical resistivity of 2.33×102 ?·cm with the highest carrier concentration of 5.28×1016 cm-3 and Hall mobility of 1.26 cm2/Vs. The conductivity type of CuO films changed from p-type to n-type when the substrate temperature was above 500 ?.The effects of Li doping on the structural, electrical and optical properties of CuO thin films were investigated. Li doping concentration increased from 1wt% to 4wt% with the crystallization quality getting better before they were bad; The optimized doping concentration is 2wt% and the lowest electrical resistivity of 7.56 ?·cm, the highest carrier concentration of 7.39×1019 cm-3, and Hall mobility of 0.017 cm2/Vs were achieved. These results are due to different position of the Li atoms in CuO crystal lattice.The effects of annealing conditions on the structural, electrical and optical properties of Li doping CuO films were investigated. As the annealing temperature increases from 500 ? to 800??1h, N2?, the Hall mobility increases from 0.0713 to 0.1661 cm2/Vs, but carrier concentration decreases from 3.46×1019 to 2.31×1019 cm-3, resistivity increases from 6.51 to 1107 ?·cm. When the temperature is above 800 ?, the conductive type of CuO films changed from p-type to n-type; As the annealing time increases from 1h to 3h?500?,N2?, Hall mobility increases from 0.0713 to 0.1235 cm2/Vs, but carrier concentration decreases from 3.46×1019 to 9.87×1018 cm-3, resistivity increased from 6.51 ?·cm to 13.36 ?·cm; Finally, the effects of O2 atmosphere annealing on the structural, electrical and optical properties of Li doping CuO films were investigated. Annealing has little effect on mobility, carrier concentration, and resistivity, but the conductive type changed from p-type to n-type. |
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