Atmospheric pressure chemical vapor deposition of transparent conducting films of fluorine doped zinc oxide and their application to amorphous silicon solar cells
- 425 Downloads
Transparent conducting ZnO:F was deposited as thin films on soda lime glass substrates by atmospheric pressure chemical vapor deposition (CVD) deposition at substrate temperatures of 480–500 °C. The precursors diethylzinc, tetramethylethylenediamine and benzoyl fluoride were dissolved in xylene. The solution was nebulized ultrasonically and then flash vaporized by a carrier gas of nitrogen preheated to 150 °C. Ethanol was vaporized separately, and these vapors were then mixed to form a homogeneous vapor mixture. Good reproducibility was achieved using this new CVD method. Uniform thicknesses were obtained by moving the heated glass substrates through the deposition zone. The best electrical and optical properties were obtained when the precursor solution was aged for more than a week before use. The films were polycrystalline and highly oriented with the c-axis perpendicular to the substrate. The electrical resistivity of the films was as low as 5 × 10−4 Ωcm. The mobility was about 45 cm2/Vs. The electron concentration was up to 3 × 1020/cm3. The optical absorption of the films was about 3–4% at a sheet resistance of 7 Ω/square. The diffuse transmittance was about 10% at a thickness of 650 nm. Amorphous silicon solar cells were deposited using the textured ZnO:F films as the front electrode. The short circuit current was increased over similar cells made with fluorine doped tin oxide, but the voltages and fill factors were reduced. The voltage was restored by overcoating the ZnO:F with a thin layer of SnO2:F.
KeywordsSnO2 Zinc Oxide TMEDA Fluorine Concentration Diethylzinc
This work was supported by the National Renewable Energy Laboratory. Steven Hegedus (Delaware) and David Carlson (Solarex) deposited and characterized the amorphous silicon solar cells. John Thornton, Keith Kramer, Dan Teff and Nicholas DiCeglie provided assistance in the chemical preparations and analyses. The authors would also like to thank Yuan Z. Lu, David Lange, and John Chervinsky for their assistance in making some of the characterization measurements.
- 4.Adachi K, Sato K, Gotoh Y, Nishimura H (1991) Proc of 22nd IEEE PVSC Google Scholar
- 6.Shiosaki T (1978) Proc IEEE Ultrasonics Symp 100Google Scholar
- 17.Jacobsohn E, Shehtman D (1992) Mat Res Soc Symp Proc 242:779Google Scholar
- 18.Brody DE, R Singh, Morgan JH, Lesli JD, Moore CJ, and A Dixon (1980) In: Proceedings of the 12th IEEE Photovoltaic Specialist Conference. IEEE, New York Google Scholar
- 20.Major S, Banergee A, Chopra KL (1986) J Mater Res 1:300Google Scholar
- 26.Minami T, Sato H, Imamoto H, Takata S (1992) Jpn J Appl Phys 31:L257; Minami T, Sato H, Sonohara H, Takata S, Miyata T, Fukuda I (1994) Thin Solid Films 253:14Google Scholar
- 33.Wang R, King LLH, Sleight A (1996) J Mater Res 11:1659Google Scholar
- 34.Hu J, Gordon RG (1991) Mat Res Soc Symp Proc 283:891Google Scholar
- 36.Dana’s System of Mineralogy, 7th Ed I 504Google Scholar
- 37.Nuffield EW (1966) X-ray diffraction methods. John Wiley & Sons, New YorkGoogle Scholar
- 40.Ahmad Nuruddin, PhD Thesis, University of Illinois, 1997; Ahmad Nuruddin and John Abelson, unpublished resultsGoogle Scholar