Development of ZnTe layers using an electrochemical technique for applications in thin-film solar cells

Abstract

Zinc telluride layers were grown by an electrochemical technique using acidic and aqueous solutions containing ZnCl 2 and TeO 2 . The layers were deposited on glass/fluorine-doped tin oxide substrates using a two-electrode system. The deposited ZnTe layers were characterized using x-ray diffraction, x-ray fluorescence, Raman spectroscopy, optical absorption, photoelectrochemical cell measurements, scanning electron microscopy and 3D-atomic force microscopy (3D-AFM) for the structural, optical, electrical and morphological properties. The electrodeposited ZnTe layers grow as columns, and have cubic crystal structure, the band gap in the range of (2.00-2.20) eV and p-type electrical conductivity. Surface morphology studies using SEM indicate the presence of two types of material clusters varying in size up to ∼125 nm. 3D-AFM studies with higher magnification show that the material tends to grow as columns with different sizes leaving gaps in between in some areas.

Growth and characterisation of n- and p-type ZnTe thin films for applications in electronic devices

“…The n-type electrical conductivity was achieved at higher cathodic potential due to Zn-richness. Fauzi et al [25] reported only p-type ZnTe even at higher cathodic potentials. This can be due to presence of higher concentrations of Te in the electrolyte.…”

“…It has been shown that Te being a nobler element deposits first [24,25] [27]. Since Te shows a more positive redox potential than Zn, it is therefore expected to deposit first.…”

“…At low cathodic deposition potential, a Te-rich ZnTe layer is expected to be formed [25]. As the deposition potential increases, the amount of Zn in the ZnTe layer gradually increases thus allowing a near stoichiometric ZnTe layer to be deposited.…”

“…The measurement was carried out to study the surface morphology, growth pattern and to also measure the grain sizes and surface roughness of ED- [25], the varying sizes of the columnar shaped thin film material leaves unwanted gaps inbetween the columnar materials. The authors showed that these undesirable gaps cause shorting of devices thus leading to a poor performance when used in solar cell fabrication.…”

“…Several techniques have been used for the deposition of ZnTe thin films. Some of these methods are: closed space sublimation (CSS) [16], hydrothermal [17], molecular beam epitaxy [11], rf-magnetron sputtering [18], metallo-organic chemical vapour deposition 3 (MOCVD) [19], metallo-organic vapour phase epitaxy (MOVPE) [20], thermal evaporation [21] and electrodeposition [22][23][24][25]. According to Mahalingam et al [24], electrodeposition (ED) technique provides a suitable method to prepare continuous and thin semiconductor films.…”