Cu rich domains and secondary phases in PVD-CdS / PVD-CuIn1−xGaxSe2 heterojunctions

He, Xiaoqing; Ercius, Peter; Bailey, Jeff; Zapalac, G.; Mackie, Neil; Bayman, Atiye; Varley, Joel B.; Lordi, Vincenzo; Rockett, Angus

doi:10.1109/pvsc.2015.7356414

Cited by 4 publications

(4 citation statements)

References 10 publications

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“…Cu2-xS phases are highly conductive and could be detrimental for solar cell performance when present in the CdS due to shunts. The identification of Cu2-xS segregates in the CdS has also been shown for physical vapour deposited CdS [43,44] indicating its formation is not unique to the CdS-CBD process.…”

Section: Relat Ion With the Literature And Discussion Of Results Smentioning

confidence: 88%

Cd and Cu Interdiffusion in Cu(In, Ga)Se₂/CdS Hetero-Interfaces

Salomé

Ribeiro‐Andrade

Teixeira

et al. 2017

IEEE J. Photovoltaics

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We report a detailed characterization of an industrylike prepared Cu(In,Ga)S e2 (CIGS)/CdS heterojunction by scanning transmission electron microscopy (S TEM) and photoluminescence (PL). Energy dispersive x-ray spectroscopy (EDS) shows the presence of several regions in the CIGS layer that are Cu deprived and Cd enriched, suggesting the segregation of Cd-S e. Concurrently, the CdS layer shows Cd-deprived regions with the presence of Cu, suggesting a segregation of Cu-S. The two types of segregations are always found together, which, to the best of our knowledge, is observed for the first time. The results indicate that there is a diffusion process that replaces Cu with Cd in the CIGS layer and Cd with Cu in the CdS layer. Using a combinatorial approach we identified that this effect is independent of focused-ion beam sample preparation and of the TEM-grid. Furthermore, photoluminescence measurements before and after an HCl etch indicate a lower degree of defects in the post-etch sample, compatible with the segregates removal. We hypothesize that Cu2-xSe nanodomains react during the chemical bath process to form these segregates since the chemical reaction that dominates this process is thermodynamically favourable. These results provide important additional information about the formation of the CIGS /CdS interface.

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Section: Relat Ion With the Literature And Discussion Of Results Smentioning

confidence: 88%

Cd and Cu Interdiffusion in Cu(In, Ga)Se₂/CdS Hetero-Interfaces

Salomé

Ribeiro‐Andrade

Teixeira

et al. 2017

IEEE J. Photovoltaics

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“…1b). In the PVDCdS/CIGS heterojunctions we studied, Cu rich domains are consistently observed and sometimes can completely replace Cd, forming a pure copper sulfide compound [15]. The compound is very close to Cu2S stoichiometry and its lattice is fully coherent with that of the CdS.…”

Section: Methodsmentioning

confidence: 83%

Intermixing and Formation of Cu-Rich Secondary Phases at Sputtered CdS/CuInGaSe₂Heterojunctions

Varley

Ercius

et al. 2016

IEEE J. Photovoltaics

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We report on direct evidence of Cd doping of the CuInGaSe2 (CIGS) surface in physical vapor deposited (PVD) CdS/CIGS heterojunctions by scanning transmission electron microscopy (STEM) and related techniques. We find Cd doping of the CIGS nearsurface region regardless of the presence or absence of Cu rich domains in the CdS for both zinc-blende (zb) and wurtzite (wz) CdS. However, we find that the Cd penetrates much farther into the CIGS when Cu-rich domains are present in the CdS. This suggests that Cu exchanges with Cd, increasing the concentration gradient for Cd in the CIGS and thus driving Cd into the CIGS surface. The Cd doping is clearly resolved at atomic resolution in aberration-corrected STEM-high angle annular dark field images. In zb-CdS/CIGS heterojunctions, Cd is shown to substitute for both Cu and Ga atoms, while in wzCdS/CIGS heterojunctions Cd seems to predominantly occupy Cu sites. Cd doping in the CIGS surface layer suggests the formation of a p-n homojunction in the CIGS, which may account for the high device efficiencies, comparable to CBD-CdS/CIGS processed structures.

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“…1b). In the PVD-CdS/CIGS heterojunctions we studied, Cu rich domains are consistently observed and sometimes can completely replace Cd, forming a pure copper sulfide compound [17].…”

Section: Methodsmentioning

confidence: 89%