Analysis of the electronic properties of all-electroplated ZnS, CdS and CdTe graded bandgap photovoltaic device configuration

Abstract

All-electrodeposited ZnS, CdS and CdTe thin layers have been incorporated in a graded bandgap solar cell structure of glass/FTO/n-ZnS/n-CdS/n-CdTe/Au have been fabricated and an average conversion efficiency of 14.18% was achieved under AM1.5 illuminated condition. Based on former work in which 10% conversion efficiency was reported, optimisation has been made to the semiconductor layers, precursors, thicknesses and the postgrowth treatment. These results demonstrate the advantages of multi-layer graded bandgap device configuration and the inclusion of gallium based post-growth treatment (CdCl 2 +Ga 2 (SO 4 ) 3 ) on the CdS/CdTe-based device structure. The fabricated devices were characterised using both current-voltage (I-V) and capacitance-voltage (C-V) techniques. Under dark I-V condition, a rectification factor (R.F.) of 10 4.8 , ideality factor (n) of 1.60 and a barrier height (ϕ b ) >0.82 eV were observed. Under AM1.5 illuminated I-V condition, shortcircuit current density (J sc ) of 34.08 mAcm -2 , open-circuit voltage (V oc ) of 730 mV, fill-factor (FF) of 0.57 and conversion efficiency of 14.18% were observed. Under dark C-V condition, doping density (N D ) of 7.79×10 14 cm -3 and a depletion width (W) of 1092 nm were achieved.In addition, the work demonstrates the capability of two-electrode system as a simplification to the conventional three-electrode system in the electrodeposition of semiconductors.

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

“…Electrodeposited cadmium telluride (CdTe) and copper indium gallium selenide (CIGS) are amongst the commonly used absorber layers in all-electrodeposited photovoltaic applications [57,89]. The versatility of the technique in the growth of all-electrodeposited configurations has been well documented [13,[90][91][92]. The band diagrams of possible n-p and n-n + large Schottky barrier junctions are shown in Figure 6 fabricated using CdS/CdTe configuration.…”

Perovskite solar cells: a deep analysis using current–voltage and capacitance–voltage techniques

“…As reported in reference [12] and other relevant publications [13][14][15] glass/FTO/n-ZnS/n-CdS/n-CdTe/Au devices are graded bandgap devices built on wide bandgap n-ZnS window layers. At the back of the absorber layer (n-CdTe), Au forms a large potential barrier height (φ b ) due to Fermi level pinning at defect level E 5 closer to the valence band.…”

“…Therefore, this structure has two hetero-junctions and a large Schottky barrier at the back, connected in parallel, because Fig. 8 Energy band diagram of the glass/FTO/n-ZnS/n-CdS/n-CdTe/ Au graded bandgap structure reported in reference [12,13]…”

“…In summary, the inorganic solar cells compared in this paper are graded bandgap solar cells fabricated on wide bandgap n-type window layers as published before [12][13][14][15].…”

“…Before moving into a deep discussion on perovskite solar cell results, it is appropriate to briefly present similar results reported [12,13] for graded bandgap solar cells fabricated with known inorganic semiconductors. These structures consist of three semiconducting layers and grown using electroplating to complete glass/FTO/n-ZnS/n-CdS/n-CdTe/Au solar cells.…”