Grain-boundary-enhanced carrier collection in CdTe solar cells.
When CdTe solar cells are doped with Cl, the grain boundaries no longer act as recombination centers but actively contribute to carrier collection efficiency. The physical origin of this remarkable effect has been determined through a combination of aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles theory. Cl substitutes for a large proportion of the Te atoms within a few unit cells of the grain boundaries. Density functional calculations reveal the mechanism, and further indicate the grain boundaries are inverted to n type, establishing local p-n junctions which assist electron-hole pair separation. The mechanism is electrostatic, and hence independent of the geometry of the boundary, thereby explaining the universally high collection efficiency of Cl-doped CdTe solar cells.
Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Chen
C
Li
Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio 43606, USA.
Yelong
Y
Wu
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
Jonathan
J
Poplawsky
Department of Materials, University of Oxford, Oxford OX13PH, United Kingdom and SuperSTEM Laboratory, Daresbury WA44AD, United Kingdom.
Timothy J
TJ
Pennycook
Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio 43606, USA.
Naba
N
Paudel
Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio 43606, USA.
Wanjian
W
Yin
School of Materials, University of Manchester, Manchester M139PL, United Kingdom.
Sarah J
SJ
Haigh
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA and Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
Mark P
MP
Oxley
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Andrew R
AR
Lupini
The Measurements and Characterization Group, National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
Mowafak
M
Al-Jassim
Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA.
Stephen J
SJ
Pennycook
Department of Physics and Astronomy, The University of Toledo, Toledo, Ohio 43606, USA.
Yanfa
Y
Yan