Defect visualization of Cu(InGa)(SeS)2 thin films using DLTS measurement

Abstract

Defect depth profiles of Cu (In1−x,Gax)(Se1−ySy)2 (CIGSS) were measured as functions of pulse width and voltage via deep-level transient spectroscopy (DLTS). Four defects were observed, i.e., electron traps of ~0.2 eV at 140 K (E1 trap) and 0.47 eV at 300 K (E2 trap) and hole traps of ~0.1 eV at 100 K (H1 trap) and ~0.4 eV at 250 K (H2 trap). The open circuit voltage (VOC) deteriorated when the trap densities of E2 were increased. The energy band diagrams of CIGSS were also obtained using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and DLTS data. These results showed that the valence band was lowered at higher S content. In addition, it was found that the E2 defect influenced the VOC and could be interpreted as an extended defect. Defect depth profile images provided clear insight into the identification of defect state and density as a function of depth around the space charge region.

Defects characterization in thin films photovoltaics materials by correlated high-frequency modulated and time resolved photoluminescence: An application to Cu(In,Ga)Se2

“…In the same way for CdS covered sample, we tried to increase the thickness of the defect layer without success, confirming the interfacial nature of these defect, located at the CIGS/CdS interface. This is in accordance with recent depth resolved DLTS experiments [27].…”

DLTS investigations on CIGS solar cells from an inline co-evaporation system with RbF post-deposition treatment

“…Segregated at grain boundaries, the Rb atoms can occupy the defects and passivate them. However, further investigations are required to verify this theory and to distinguish between point and extended defects, for example through dependencies of the pulse width [18,19].…”

Investigation on the properties of Cu 2 ZnSnSe 4 and Cu 2 ZnSn(S,Se) 4 absorber films prepared by magnetron sputtering technique using Zn and ZnS targets in precursor stacks

“…Another reason for the large voids' formation at the absorber/Mo interface might be the diffusion of Cu element because of the initial Cu‐rich composition of the precursor films. Furthermore, different size and amount of the voids in the samples A1 and A2 might be associated to the different lowermost layers (Zn or ZnS) in the precursor stacks and their different melting points as mentioned above 66‐68 . As seen in Figure 6F, the sample A2 showed large thickness variations due to the poor adhesion between CZTSSe and Mo layers.…”

“…Furthermore, different size and amount of the voids in the samples A1 and A2 might be associated to the different lowermost layers (Zn or ZnS) in the precursor stacks and their different melting points as mentioned above. [66][67][68] As seen in Figure 6F, the sample A2 showed large thickness variations due to the poor adhesion between CZTSSe and Mo layers. To conclude, it was revealed out from the cross sectional SEM images that the sample A1 exhibited the films with more uniform thickness, denser and far fewer voids compared to the sample A2 ( Figure 6C,F), and both of the films were composed of large grains throughout the whole thickness growing from Mo back contact layer to the surface.…”