Effect of thickness: a case study of electrodeposited CdS in CdS/CdTe based photovoltaic devices

Abstract

The effect of electrodeposition technique on CdS thickness incorporated in CdS/CdTe-based solar cell has been investigated using all-electrodeposited g/FTO/n-CdS/n-CdTe/p-CdTe multilayer device configuration. The optical, morphological and structural properties of the electroplated CdS were investigated for CdS thicknesses between 50nm and 200 nm. The observed CdS bandgap ranges between 2.42 and 2.46 eV. The morphological analysis shows full coverage of underlying g/FTO substrate for all CdS thicknesses except for the 50 nm which shows the presence of gap in-between grains. The structural analysis shows a preferred orientation of H(101) for all the CdS thicknesses except the 50 nm thick CdS which shows either a weak crystallinity or an amorphous nature. The fabricated solar cell shows a maximum conversion efficiency of ~11% using CdS thickness ranging between 100 and 150 nm. These results show that although low CdS thickness is desirable for photovoltaic application, the effect of nucleation mechanism of deposition technique should be taken into consideration.

Electroplating of Semiconductor Materials for Applications in Large Area Electronics: A Review

“…For the three-electrode configuration, the potential difference is measured across the working and the reference electrodes, while the measured current is between the working and the counter electrodes. In general, other factors such as the pH of the electrolyte [18], applied deposition potential [13,14], deposition temperature [19], stirring rate [20], deposition current density, duration of deposition and thickness [21], underlying substrate [22], and concentration of ions in the deposition electrolyte [18] affects the electrodeposition process and the properties of the deposited layers. Recent publications have demonstrated the similarities between electrodeposited semiconductors using three-electrode and two-electrode electroplating configurations [23,24].…”

“…The nucleation of the electroplated material spreads out through to the lowest valley from the initiation rough surface peaks resulting into columnar nature of the deposited layers [14]. The potency of this mechanism is highly influential at the initial stages of deposition due to unevenness of the deposited layer thickness characterised by pin-holes, voids, gaps, and high dislocation density within the semiconductor material [21]. This characteristic property is detrimental when a thin semiconductor layer with a thickness of <100 nm is required [21].…”

“…The potency of this mechanism is highly influential at the initial stages of deposition due to unevenness of the deposited layer thickness characterised by pin-holes, voids, gaps, and high dislocation density within the semiconductor material [21]. This characteristic property is detrimental when a thin semiconductor layer with a thickness of <100 nm is required [21].…”

Unravelling complex nature of CdS/CdTe based thin film solar cells

“…ED also provides an excellent technique for fine controlling of the CdS layer thickness. High efficiency solar cells are produced with ~50-100 nm thick CdS layers [65]. This layer undergoes a heat treatment in air at ~400 °C for 20 min before depositing CdTe layers.…”

Progress in development of graded bandgap thin film solar cells with electroplated materials

“…Ojo et al [47] took into consideration the electroplating mechanism, effect of CdS thickness and parasitic absorption. Based on these findings, 120 nm thick CdS layer was utilised using 0.3 M CdCl 2 and 0.03 M (NH 4 ) 2 S 2 O 3 [24] while the CdTe layer was electrodeposited from an aqueous electrolyte containing 1 M Cd(NO 3 ) 2 and ~1 mM TeO 2 [28].…”