The effect of Na on the electronic properties of Cu(In,Ga)Se2 thin films: A local‐probe study |
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| Authors: | D Azulay D Abou‐Ras I Popov I Balberg O Millo |
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| Institution: | 1. Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem, Israel;2. Azrieli, College of Engineering, Jerusalem, Israel;3. Helmholtz‐Zentrum Berlin für Materialien und Energie, Berlin, Germany;4. The Hebrew University Center for Nanoscience and Nanotechnology, Jerusalem, Israel |
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| Abstract: | We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn0.7Ga0.3Se2 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) |
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| Keywords: | Cu(In Ga)Se2 grain boundaries scanning tunneling spectroscopy electronic properties |
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