A pyrosol process to deposit large-area SnO2:F thin films and its use as a transparent conducting substrate for CdTe solar cells

Highly transparent, low-resistance SnO2 :F films suitable as a substrate material for thin-film CdS/CdTe solar cells have been developed on 10 x 10, 30 x 60 and 82 x 71cm(2) glass substrates by an ultrasonic spray pyrolysis (pyrosol) process. Dimethyltin dichloride, NH,F and HF dissolved in water served as the source solution. A fine spray of the source solution has been transported using air as a carrier gas onto hot glass plates in a belt furnace maintained at 500-530 degreesC. A very high growth rate of > 15 nm/s and a high throughput of 3 min/glass plate (82 x 71cm(2) size) have been achieved with films showing greater uniformity, low sheet resistance and high optical transmission. Typical films exhibited a thickness of 500 nm, a sheet resistance of 8.1 Omega /sq., a mobility of 43.8 cm(2)/V s and a donor concentration of 3.5 x 10(20) cm(-3). A thin-film CdS/CdTe solar cell fabricated on a 30 x 60 cm(2) SnO2:F transparent conducting substrate exhibited a solar energy conversion efficiency maximum of 14.95% for 1 cm(2) cell and an average efficiency of 14.24% for 178 isolated 1 cm(2) cells. (C) 2001 Elsevier Science B.V. All rights reserved.