Evaluation of the Effect of Deposition pH on the Physico-chemical Properties of Electrochemically Deposited Cadmium Telluride for Photovoltaic Device Applications

Abstract

Two-electrode (2E) configuration was successfully utilised in the electrochemical deposition of cadmium telluride (CdTe) on fluorine-doped tin oxide (FTO) substrate with the main emphasis on the electrolytic bath pH. The electrochemical deposition pH explored is within the range of (1.00 to 6.00)±0.02 for the aqueous electrolyte comprising of tellurium oxide (TeO2) and cadmium nitrate (Cd(NO3)2) which are the respective precursors of Te and Cd. The optical, structural, morphological, compositional, and electrical properties of the electroplated CdTe thin-films were respectively explored using UV-Vis spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and photoelectrochemical (PEC) cell measurements. The optical characterisation show that the CdTe samples exhibit dissimilar absorbance depending on the growth pH for both the as-deposited layers and post-growth treated CdTe layers. A decrease in the absorption edge slope and dip in the bandgap was observed away from pH2. The bandgap of the post-growth treated CdTe layers showed enhancement as it leans towards 1.45 eV, with the trend retention of absorption edge slope, similar to the as-deposited CdTe layers. The electrodeposited CdTe thin-films show a dominant orientation along the cubic (111) CdTe plane, while both the the calculated crystallite size and the XRD peak intensity Pi decreases with the electroplating pH outside the (2.00 to 3.00)±0.02 range. The EDX analyses depicts an alteration in the ratio of Cd to Te atomic percentage relative to the pH of the electrolyte. Comparatively high Te atomic ratio was observed at lower pH values and vice versa with increase alkalinity of the electrolyte. The obtained morphology depicts that the underlying FTO layers are well covered with a gradual reduction in the grain size of the CdTe observable away from pH value (2.00 and 3.00). The photoelectrochemical cell study depicts that the conduction type of the CdTe layers can also be attributed to the CdTe-electrolytic bath pH value.

Influence of growth time on the properties of CdTe thin films grown by electrodeposition using acetate precursor for solar energy application

“…The CdS/CdTe solar cell has been recognized as one of the potential possibilities for developing sound photovoltaic systems [5]. CdTe has recently gained attention due to its many applications, such as photovoltaics [6], x-ray sensors [7], solar energy water splitting [8], imaging detectors [9], optoelectronics [10], and radiation detectors [11].…”

“…The structure, morphology, surface roughness, and optical properties of CdTe thin films depend on the growth method and optimization of growth parameters [5]. There are several methods to grow CdTe thin films, such as vacuum evaporation [12], chemical molecular beam deposition (CMBD) method [13], close space sublimation (CSS) [14], physical vapour deposition [15], successive ionic layer adsorption and reaction (SILAR) [16], pulsed laser deposition (PLD) [17], metal-organic chemical vapour deposition (MOCVD) [18], coprecipitation [19], Radio frequency (RF) sputtering [20], sol-gel [21], chemical bath deposition (CBD) [22] and electrodeposition (ED) [23].…”