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The effect of Na on the electronic properties of Cu(In,Ga)Se 2 thin films: A local‐probe study
Author(s) -
Azulay D.,
AbouRas D.,
Popov I.,
Balberg I.,
Millo O.
Publication year - 2016
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201600058
Subject(s) - grain boundary , band bending , passivation , crystallite , materials science , vacancy defect , scanning tunneling microscope , quantum tunnelling , band gap , condensed matter physics , spectroscopy , crystallography , chemistry , optoelectronics , nanotechnology , microstructure , metallurgy , physics , layer (electronics) , quantum mechanics
We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn 0.7 Ga 0.3 Se 2 thin films using scanning tunneling microscopy and spectroscopy. The tunneling spectra indicate a reduced in‐gap density of states at grain boundaries and reveal a downward band‐bending in Na‐rich grain boundaries with respect to the adjacent grains, in agreement with our conductive atomic force microscopy data. It thus appears that Na passivates deep‐level defects at grain boundaries and induces a downward band‐bending there. Moreover, we provide evidence that Na passivates mainly Cu vacancy related defects. We suggest that the grain‐boundary passivation, which reduces the recombination rate of photogenerated carriers, is at least of major importance in the well known Na‐induced improvement in the efficiency of the corresponding solar cells. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)