Investigation of doped a-Si1-xCx:H as a novel back contact material for CdTe solar cells

Prakash Koirala, Zhiquan Huang, Maxwell Junda, Nikolas J. Podraza, Sylvain Marsillac, Angus A. Rockett, Robert W. Collins

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Wide band-gap, p-type doped, hydrogenated amorphous silicon-carbon alloy (a-Si1-xCx:H:B) layers deposited by plasma enhanced chemical vapor deposition (PECVD) under conditions that yield efficient hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells have been applied as back contacts to sputter-deposited CdTe superstrate solar cells. We report a maximum observed Voc of 0.78 V and a best initial efficiency of ∼ 7.7 % (relative to an ∼ 12% standard cell baseline) without the introduction of Cu into the back contact region. We studied the stability of the best performing cells over a two year time period and found that although Voc is relatively stable, the series resistance of the cells increased significantly leading to fill-factor degradation. The role of hydrogen loss from the back contact layer via diffusion into the CdTe absorber is explored as a possible cause of this degradation. In related investigations, we have found that the effect of in-diffusing H on the CdTe solar cell performance is detrimental, as observed from a brief (∼ 15 s) exposure of CdTe to a low power H2 plasma between the treatment by CdCl2 and the application of standard Cu/Au back contacts. This detrimental effect of H in the fabrication of the back contact layer from hydride gases, and the subsequent instability of the back contact itself, were found to be significant challenges encountered in this investigation.

Original languageEnglish (US)
Title of host publication2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014
PublisherInstitute of Electrical and Electronics Engineers Inc.
Number of pages6
ISBN (Electronic)9781479943982
StatePublished - Oct 15 2014
Externally publishedYes
Event40th IEEE Photovoltaic Specialist Conference, PVSC 2014 - Denver, United States
Duration: Jun 8 2014Jun 13 2014

Publication series

Name2014 IEEE 40th Photovoltaic Specialist Conference, PVSC 2014


Other40th IEEE Photovoltaic Specialist Conference, PVSC 2014
Country/TerritoryUnited States


  • CdS/CdTe
  • hydrogenated amorphous silicon
  • novel back contact
  • photovoltaic cells

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials


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