Pinhole free thin film CdS deposited by chemical bath using a substrate reactive plasma treatment

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, <100 nm thickness, were deposited on both O2/Ar plasma cleaned and conventionally cleaned substrates. We show that the O2/Ar plasma treatment of the TEC 15 substrate reduced the water contact angle from ∼55° to less than 12° 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 O2/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.

The structural properties of CdS deposited by chemical bath deposition and pulsed direct current magnetron sputtering

“…The substrates were cleaned in a two-step ultrasonic bath process followed by a plasma surface treatment prior to the CdS film growth [20]. CdS thin films of~100 nm thickness were deposited by pulsed DC magnetron sputtering in a 'PV Solar' magnetron sputtering system (Power Vision Ltd., Crewe UK); details of the system have been provided elsewhere [18].…”

“…The bath solution consisted of 200 ml of de-ionised water, 15 ml of Cd(CH 3 COO) 2 0.01 M, Thin Solid Films xxx (2014) xxx-xxx 25 ml of NH 4 OH 25% and 10 ml of CS(NH 2 ) 2 , 0.1 M. An ultrasonic probe was immersed in the solution to accelerate the reaction kinetics [20].…”

Comparison Between Performances of In2O3 and In2TiO5-Based EIS Biosensors Using Post Plasma CF4 Treatment Applied in Glucose and Urea Sensing

“…The deviation in surface potential of the sensing surface after the surface is dipped into solutions with different pH values was determined by the C-V shift. H + and OH − attachment at the corresponding binding sites at the sensing surface can alter the surface potential 29 . The present results demonstrate that Ti doping increases the numbers of binding sites on the sensing surface.…”

Synthesis of CdS with Large Band Gap Values by a Simple Route at Room Temperature

“…Our results indicate that oxygen is helpful to obtain clean, compact and small CdS grains, which is similar to the reported results. 17,18 CdS thin films with much more clean, compact and smaller grains are helpful to reduce the possibility of shunting path formation in the CdTe solar cells. 17 Transmission spectra of samples a-e are present in Fig.4(A).…”