Optimisation of pH of the CdCl2 + Ga2(SO4)3 activation step of CdS/CdTe based Thin-Film solar cells

Abstract

In order to produce high efficiency solar cells based on CdTe, CdCl 2 post-growth treatment is an essential processing step. This treatment can be further improved by adding elements such as Fluorine and Gallium into the CdCl 2 solution. Through systematic experimentation, it has been found that the pH value of the treatment solution also affect the conversion efficiency of the solar cells. This work therefore focuses on the effect of pH value of CdCl 2 +Ga 2 (SO 4) 3 aqueous solution on the device efficiencies. The graded bandgap device structure, glass/FTO/n-ZnS/n-CdS/n-CdTe/Au was used in this work. The pH values of 1.00, 2.00 and 3.00 for CdCl 2 +Ga 2 (SO 4) 3 solutions were utilised for the activation of glass/FTO/n-ZnS/n-CdS/n-CdTe layers and its effects were explored for both the CdTe material and device properties. It has been found that both CdTe material properties and solar cell device properties are superior when the pH value of 2.00 is used for post-growth treatment. The best conversion efficiency observed in this work for the above graded bandgap device is 12.2%.

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

“…It is well documented that electrodeposited layers with an emphasis on semiconductors often require post-deposition treatment to further improve their structural, morphological, compositional, and optical properties [81][82][83]. It is, although, arguable that other semiconductor deposition techniques such as [77], MOCVD [84], and CSS [85] also require such treatments, as it is evident in the performances of the applications utilised for References [81][82][83].…”

“…The electronic properties of the fabricated photovoltaic cells obtained using current-voltage (I-V) and capacitance-voltage (C-V) techniques are summarised in Table 2. techniques such as [77], MOCVD [84], and CSS [85] also require such treatments, as it is evident in the performances of the applications utilised for References [81][82][83]. Asides semiconductors, other issues such as the influence of different process conditions on mechanical properties of electroplated materials and the control of the integrity of the electroplated layers as it relates to further processing have also been the raised [86,87], but not discussed in this communication.…”