Modayemzadeh Hamed Reza, Varnamkhasti Mohsen Ghasemi, Zabolian Hosein
Department of Physics, Faculty of Sciences, Isfahan University, Isfahan, Iran.
Appl Opt. 2013 May 20;52(15):3444-50. doi: 10.1364/AO.52.003444.
In this study, nanocrystalline Sn-doped In(2)O(3) (ITO) films were deposited by electron beam evaporation technique and were annealed in air atmosphere from 300°C to 500°C for 30 min. Then, the annealed ITO films in air at 450°C were reannealed in vacuum for 1 h at different temperatures from 300°C to 500°C. The effects of reannealing temperature on structural, electrical, and optical properties of the ITO films were investigated. Increasing reannealing temperature from 300°C to 500°C reduced sheet resistance of ITO thin films from 38 to 12(Ω/sq). The highest transparency over the visible wavelength region of spectrum (95%) was obtained for reannealed films at 450°C. The optimum reannealing temperature for these films is 450°C. Refractive index at 550 nm and porosity for ITO films reannealed at 450°C were 1.92% and 21.2%, respectively. The allowed direct bandgap at different reannealing temperature was evaluated to be in the range of 4.1-4.28 eV. X-ray diffraction results showed that the reannealed films were polycrystalline and a rise in grain size was observed in them. The average grain size in the films reannealed in vacuum at 450°C is about 48.6 nm. Atomic force microscope images indicated that the grain size and root-mean-square roughness films depend on the reannealing temperature. It has been found that reannealing temperature is a key factor in controlling the structural, electrical, and optical properties of ITO films. The power conversion efficiency of the device with ITO films reannealed at 450°C is 1.22% and it is about 58% higher than that of the device without it. This indicates that this film is a promising transparent electrode for organic photovoltaic cells.
在本研究中，采用电子束蒸发技术沉积了纳米晶掺锡氧化铟（ITO）薄膜，并在空气气氛中于300°C至500°C退火30分钟。然后，将在空气中450°C退火的ITO薄膜在真空中于300°C至500°C的不同温度下再退火1小时。研究了再退火温度对ITO薄膜结构、电学和光学性能的影响。将再退火温度从300°C提高到500°C，ITO薄膜的方块电阻从38降低到12（Ω/sq）。在450°C再退火的薄膜在可见光谱波长区域获得了最高透明度（95%）。这些薄膜的最佳再退火温度为450°C。在550nm处的折射率和在450°C再退火的ITO薄膜的孔隙率分别为1.92%和21.2%。在不同再退火温度下允许的直接带隙评估为4.1 - 4.28eV。X射线衍射结果表明，再退火薄膜为多晶，且观察到其晶粒尺寸增大。在450°C真空中再退火的薄膜的平均晶粒尺寸约为48.6nm。原子力显微镜图像表明，薄膜的晶粒尺寸和均方根粗糙度取决于再退火温度。已发现再退火温度是控制ITO薄膜结构、电学和光学性能的关键因素。在450°C再退火的ITO薄膜器件的功率转换效率为1.22%，比没有该薄膜的器件高出约58%。这表明该薄膜是用于有机光伏电池的有前景的透明电极。
