Keh-moh Lin ∗, Paijay Tsai Department of Mechanical Engineering, Southern Taiwan University of Technology, No. 1, Nantai St., Yung-Kang City, Tainan 710, Taiwan, ROC Received 12 September 2006; received in revised form 28 December 2006; accepted 20 January 2007 Parametric study on preparation and characterization of ZnO:Al films by sol–gel method for solar cells Materials Science and Engineering B 139 (2007) 81–87 日期 ： 指導老師 ： 林克默 博士 黃文勇 博士 學生 ： 郭怡彣

Outline 1. Introduction 2. Experimental procedure 3. Results and discussion 4. Conclusions

1. Introduction Sol–gel technique has been receiving high attention since it enables us to develop low-cost and simple deposition procedure to obtain high quality TCO films. The main goal of this study is to examine the influences of the preparation parameters on electrical resistivity, optical transmittance, crystallite size and crystallinity of AZO films so that these films can be applied on thin film solar cells. 1

2. Experimental procedure The flow chart shows the procedure for preparing ZnO:Al films by sol–gel method. 2

3. Results and discussion X-ray diffraction of AZO films with Tpre-heat = 500, 600 and 700 ◦ C,0.3 M, Al/Zn = 4 at.%, five layers. 3

X-ray diffraction ofAZOfilms with Tpre-heat = 600 ◦ Cand Tpost-heat = 500,600 and 700 ◦ C, 0.3 M, Al/Zn = 4 at.%, five layers. 4

Surface morphology of AZO films, 0.5 M, Al/Zn = 2 at.%, pre-heated by 600 ◦ C in air, and post-heated by 600 ◦ C under vacuum: (a–e) present layer number 1–5, respectively; (f) gives the cross-section of the five layers film. 5

Film thickness depends on the number of layers and precursor concentration, Al/Zn = 4 at.%, 600 ◦ C/600 ◦ C. 6

The sheet resistance distribution with respect to Al-doping concentration, single layer films annealed under vacuum ( ∼ 1mTorr). 7

Film resistance vs. layer number under different procedure conditions. 8

Hall measurements of AZO films. 9

Film transmittance, 0.5 M, Al/Zn = 2 at.%, 600 ◦ C/600 ◦ C. 10

4. Conclusions We found that the annealing temperatures affected the crystallinility of the AZO films considerably, but the controlling of effective doping concentration was the key point to achieve low film resistance by sol–gel method. Experimental results indicated that the multilayered structure can improve film resistivity. This was achieved by the rapidly rising carrier concentration and the slowly increasing carrier mobility as the film became thicker. 11

Thank you for your attention 12