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Title: Electron-Selective TiO2 Contact for Cu(In,Ga)Se2 Solar Cells

The non-toxic and wide bandgap material TiO2 is explored as an n-type buffer layer on p-type Cu(In,Ga)Se2 (CIGS) absorber layer for thin film solar cells. The amorphous TiO2 thin film deposited by atomic layer deposition process at low temperatures shows conformal coverage on the CIGS absorber layer. Solar cells from non-vacuum deposited CIGS absorbers with TiO2 buffer layer result in a high short-circuit current density of 38.9 mA/cm2 as compared to 36.9 mA/cm2 measured in the reference cell with CdS buffer layer, without compromising open-circuit voltage. The significant photocurrent gain, mainly in the UV part of the spectrum, can be attributed to the low parasitic absorption loss in the ultrathin TiO2 layer (~10 nm) with a larger bandgap of 3.4 eV compared to 2.4 eV of the traditionally used CdS. Overall the solar cell conversion efficiency was improved from 9.5% to 9.9% by substituting the CdS by TiO2 on an active cell area of 10.5 mm2. In conclusion, optimized TiO2/CIGS solar cells show excellent long-term stability. The results imply that TiO2 is a promising buffer layer material for CIGS solar cells, avoiding the toxic CdS buffer layer with added performance advantage.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [2] ;  [2] ;  [3] ;  [2]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Industrial Technology Research Institute, Hsinchu (Taiwan). Green Energy & Environment Research Laboratorie
  2. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
  3. Industrial Technology Research Institute, Hsinchu (Taiwan). Green Energy & Environment Research Laboratorie
  4. Univ. of California, Berkeley, CA (United States)
Publication Date:
OSTI Identifier:
1256061
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 5; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY