Achieving a pinhole-free CdS layer is necessary to produce high performance thin film CdTe solar cells. Pinholes in the CdS layer can compromise the efficiency of a CdTe solar cell by causing shunts. We have investigated the use of a plasma treatment of a fluorine doped tin oxide coated glass substrate (NSG TEC 15) and its effect on pinhole reduction in thin film CdS layers grown by Chemical Bath Deposition. CdS films, <100nm thickness, were deposited on both O-2/Ar plasma cleaned and conventionally cleaned substrates. We show that the O-2/Ar plasma treatment of the TEC 15 substrate reduced the water contact angle from similar to 55 degrees to less than 12 degrees indicating a substantial increase in the surface energy. The CdS deposited on the plasma treated TEC 15 was pinhole free, very smooth and homogenous in morphology and composition. Scanning electron microscopy images show that the O-2/Ar plasma treatment is effective in increasing film density and grain size. Corresponding spectroscopic ellipsometry measurements show an increase in the refractive index from 2.18 to 2.43 at 550 nm wavelength. (C) 2013 AIP Publishing LLC.
Pinhole free thin film CdS deposited by chemical bath using a substrate reactive plasma treatment
Losurdo M;
2014
Abstract
Achieving a pinhole-free CdS layer is necessary to produce high performance thin film CdTe solar cells. Pinholes in the CdS layer can compromise the efficiency of a CdTe solar cell by causing shunts. We have investigated the use of a plasma treatment of a fluorine doped tin oxide coated glass substrate (NSG TEC 15) and its effect on pinhole reduction in thin film CdS layers grown by Chemical Bath Deposition. CdS films, <100nm thickness, were deposited on both O-2/Ar plasma cleaned and conventionally cleaned substrates. We show that the O-2/Ar plasma treatment of the TEC 15 substrate reduced the water contact angle from similar to 55 degrees to less than 12 degrees indicating a substantial increase in the surface energy. The CdS deposited on the plasma treated TEC 15 was pinhole free, very smooth and homogenous in morphology and composition. Scanning electron microscopy images show that the O-2/Ar plasma treatment is effective in increasing film density and grain size. Corresponding spectroscopic ellipsometry measurements show an increase in the refractive index from 2.18 to 2.43 at 550 nm wavelength. (C) 2013 AIP Publishing LLC.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
