TY - GEN
T1 - Response of CdS/CdTe devices to Te exposure of back contact
AU - Gessert, T. A.
AU - Burst, J. M.
AU - Ma, J.
AU - Wei, S. H.
AU - Kuciauskas, D.
AU - Barnes, T. M.
AU - Duenow, J. N.
AU - Young, M. R.
AU - Rance, W. L.
AU - Li, J. V.
AU - Dippo, P.
PY - 2012/11/26
Y1 - 2012/11/26
N2 - Theoretical predictions of thin-film CdS/CdTe photovoltaic (PV) devices have suggested performance may be improved by reducing recombination due to Te-vacancy (VTe) or Te-interstitial (Tei) defects. Although formation of these intrinsic defects is likely influenced by CdTe deposition parameters, it also may be coupled to formation of beneficial cadmium vacancy (VCd) defects. If this is true, reducing potential effects of VTe or Tei may be difficult without also reducing the density of VCd. In contrast, post-deposition processes can sometimes afford a greater degree of defect control. Here we explore a post-deposition process that appears to influence the Te-related defects in polycrystalline CdTe. Specifically, we have exposed the CdTe surface to Te prior to ZnTe:Cu/Ti contact-interface formation with the goal of reducing VTe but without significantly reducing VCd. Initial results show that when this modified contact is used on a CdCl2-treated CdS/CdTe device, significantly poorer device performance results. This suggests two things: First, the amount of free-Te available during contact formation (either from chemical etching or CuTe or ZnTe deposition) may be a more important parameter to device performance than previously appreciated. Second, if processes have been used to reduce the effect of VTe (e.g., oxygen and chlorine additions to the CdTe), adding even a small amount of Te may produce detrimental defects.
AB - Theoretical predictions of thin-film CdS/CdTe photovoltaic (PV) devices have suggested performance may be improved by reducing recombination due to Te-vacancy (VTe) or Te-interstitial (Tei) defects. Although formation of these intrinsic defects is likely influenced by CdTe deposition parameters, it also may be coupled to formation of beneficial cadmium vacancy (VCd) defects. If this is true, reducing potential effects of VTe or Tei may be difficult without also reducing the density of VCd. In contrast, post-deposition processes can sometimes afford a greater degree of defect control. Here we explore a post-deposition process that appears to influence the Te-related defects in polycrystalline CdTe. Specifically, we have exposed the CdTe surface to Te prior to ZnTe:Cu/Ti contact-interface formation with the goal of reducing VTe but without significantly reducing VCd. Initial results show that when this modified contact is used on a CdCl2-treated CdS/CdTe device, significantly poorer device performance results. This suggests two things: First, the amount of free-Te available during contact formation (either from chemical etching or CuTe or ZnTe deposition) may be a more important parameter to device performance than previously appreciated. Second, if processes have been used to reduce the effect of VTe (e.g., oxygen and chlorine additions to the CdTe), adding even a small amount of Te may produce detrimental defects.
UR - http://www.scopus.com/inward/record.url?scp=84869387360&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84869387360&partnerID=8YFLogxK
U2 - 10.1109/PVSC.2012.6318261
DO - 10.1109/PVSC.2012.6318261
M3 - Conference contribution
AN - SCOPUS:84869387360
SN - 9781467300643
T3 - Conference Record of the IEEE Photovoltaic Specialists Conference
SP - 3212
EP - 3216
BT - Program - 38th IEEE Photovoltaic Specialists Conference, PVSC 2012
T2 - 38th IEEE Photovoltaic Specialists Conference, PVSC 2012
Y2 - 3 June 2012 through 8 June 2012
ER -
