Investigating the electronic properties of Al{sub 2}O{sub 3}/Cu(In,Ga)Se{sub 2} interface
- ICTEAM, Université catholique de Louvain, Louvain-la-Neuve, 1348 (Belgium)
- Ångström Solar Center, University of Uppsala, Uppsala, 75121 (Sweden)
Atomic layer deposited (ALD) Al{sub 2}O{sub 3} films on Cu(In,Ga)Se{sub 2} (CIGS) surfaces have been demonstrated to exhibit excellent surface passivation properties, which is advantageous in reducing recombination losses at the rear metal contact of CIGS thin-film solar cells. Here, we report, for the first time, experimentally extracted electronic parameters, i.e. fixed charge density (Q{sub f}) and interface-trap charge density (D{sub it}), for as-deposited (AD) and post-deposition annealed (PDA) ALD Al{sub 2}O{sub 3} films on CIGS surfaces using capacitance–voltage (C-V) and conductance-frequency (G-f) measurements. These results indicate that the AD films exhibit positive fixed charges Q{sub f} (approximately 10{sup 12} cm{sup −2}), whereas the PDA films exhibit a very high density of negative fixed charges Q{sub f} (approximately 10{sup 13} cm{sup −2}). The extracted D{sub it} values, which reflect the extent of chemical passivation, were found to be in a similar range of order (approximately 10{sup 12} cm{sup −2} eV{sup −1}) for both AD and PDA samples. The high density of negative Q{sub f} in the bulk of the PDA Al{sub 2}O{sub 3} film exerts a strong Coulomb repulsive force on the underlying CIGS minority carriers (n{sub s}), preventing them to recombine at the CIGS/Al{sub 2}O{sub 3} interface. Using experimentally extracted Q{sub f} and D{sub it} values, SCAPS simulation results showed that the surface concentration of minority carriers (n{sub s}) in the PDA films was approximately eight-orders of magnitude lower than in the AD films. The electrical characterization and estimations presented in this letter construct a comprehensive picture of the interfacial physics involved at the Al{sub 2}O{sub 3}/CIGS interface.
- OSTI ID:
- 22492117
- Journal Information:
- AIP Advances, Vol. 5, Issue 10; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 2158-3226
- Country of Publication:
- United States
- Language:
- English
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