Oxidation of CdTe thin film in air coated with and without a CdCl₂ layer

Abstract

During the fabrication process of a CdS/CdTe solar cell, oxygen is often present or intentionally introduced in the CdTe growth and annealing atmospheres. In this study a comparative study was carried out on the oxidation of thin CdTe films during the annealing process in air when coated with and without a CdCl2 layer, respectively. It was found that the presence of a thin CdCl2 coating layer on the CdTe film surface enhanced the oxidation of the CdTe surface. Near the film surface, the film was composed of a low‐melting eutectic mixture of CdTe and oxides of CdTe and Te. The formation of the low‐melting mixture was assisted by the much lowered melting point of CdCl2, the presence of oxides, and the CdTe compound. This low‐melting layer enhanced the oxygen reaction with the CdTe film. The dominant oxide was CdTeO3. A CdTe solar cell with an efficiency of 9.9% was fabricated with a CdTe film subjected to an annealing in air at 400 °C with the presence of a CdCl2 coating layer.

Ultrathin Single‐Crystalline CdTe Nanosheets Realized via Van der Waals Epitaxy

“…[35][36][37] As shown in Figure 2d, two peaks stemmed from Cd 3d 3/2 and Cd 3d 5/2 states in CdTe are observed at binding energies of 413.1 and 406.3 eV, respectively. [35] Similar to tellurium oxide, the other two peaks located at higher binding energies of 414.4 and 407.6 eV are likely originated from cadmium oxide. [38] This strong splitting can be attributed to the abundant unsaturated dangling bonds on the surface of ultrathin nanosheets, which are easily oxidized.…”

“…In Figure 2c, the two peaks at 585.1 and 574.7 eV clearly indicate the existence of Te 3d 3/2 and Te 3d 5/2 from CdTe. [35] While the other two peaks at higher binding energies of 588.6 and 578.1 eV are assigned to the tellurium oxide that is formed due to surface oxidation. [35][36][37] As shown in Figure 2d, two peaks stemmed from Cd 3d 3/2 and Cd 3d 5/2 states in CdTe are observed at binding energies of 413.1 and 406.3 eV, respectively.…”

“…[35] While the other two peaks at higher binding energies of 588.6 and 578.1 eV are assigned to the tellurium oxide that is formed due to surface oxidation. [35][36][37] As shown in Figure 2d, two peaks stemmed from Cd 3d 3/2 and Cd 3d 5/2 states in CdTe are observed at binding energies of 413.1 and 406.3 eV, respectively. [35] Similar to tellurium oxide, the other two peaks located at higher binding energies of 414.4 and 407.6 eV are likely originated from cadmium oxide.…”

Stable CdTe thin film solar cells with a MoOx back‐contact buffer layer

“…It is clearly shown that the as‐prepared CdTe had oxide, identified as TeO 2 , on the surface. Our previous study showed that the dominant oxide was CdTeO 3 . The oxide layer on the surface of CdTe was a high‐resistive layer, which induced a valance band bending leading to the roll‐over phenomenon shown in Figure (a).…”

“…In our CdTe cell fabrication procedure, all the CdTe films were subjected to a CdCl 2 annealing process to activate the CdTe films. Therefore, an oxide layer, which was mainly composed of CdTeO 3 , was formed on the CdTe surface as evidenced by the XPS spectrum shown in Figure (b) .…”