A Pyrosol Technique to Deposit Highly Transparent, Low-Resistance SnO2:F Thin Films from Dimethyltin Dichloride.

Highly transparent, low-resistance SnO{sub 2}:F films suitable as a substrate material for thin film CdS/CdTe solar cells have been developed on 10 {times} 10 cm glass substrates by an ultrasonic spray pyrolysis (pyrosol) technique using dimethyltin dichloride (DMTDC) as a tin source. DMTDC, NH{sub 4}F, and HF, all dissolved in water, served as the source solution. An ultrasonic vibrator operated at 1.5 MHz produced a fine spray of the source solution. It was transported, using air as a carrier gas, to moving glass plates in a belt furnace maintained at 530 C. A very high growth rate of nearly 100 {angstrom}/s was realized in this process with good homogeneity, high transparency, and low resistivity. Films with a sheet resistance of less than 10 {Omega}/{open_square} have been routinely prepared and their preparation technology has been well established. A proper nozzle design and exhaust system to remove the spent gases determines the technology of obtaining spot and cloud free homogeneous films in the belt furnace. A film of 5000 {angstrom} thickness exhibited the lowest electrical resistivity, of 3.9 {times} 10{sup {minus}4} {Omega} cm, a mobility value of 38 cm{sup 2}/V s, and a donor concentration of 4.16 {times} 10{sup 20} cm{sup {minus}3}.more » Films of 5000--6000 {angstrom} thickness having an average transmittance of nearly 85% in the visible range and a sheet resistance of around 8 {Omega}/{open_square} were used as transparent conducting oxide film substrates to fabricate thin film CdS/CdTe solar cells. A solar energy conversion efficiency of over 14% was achieved.« less