Distinction between bulk and interface states in CuInSe2/CdS/ZnO by space charge spectroscopy
R. Herberholz , Małgorzata Igalson , H. W. Schock
AbstractWe present a detailed study of admittance spectroscopy and deep level transient spectroscopy on CuInSe2/CdS/ZnO thin film solar cells. The admittance spectra reveal an emission from a distribution of hole traps centered at an activation energy of 280 meV and a shallower level with a sharp activation energy of \#x223c; 120 meV. After repetitive annealing of the device in air at 200 \#x2009; \#xb0;C, the activation energy of the latter level increases continuously from 120 to 240 meV, while the 280 meV hole traps remain unaffected. Deep level transient spectroscopy with optical excitation reveals an emission of minority carriers with time constants comparable to those observed for the shallow level in admittance spectroscopy. The shift of the activation energy after annealing also occurs in deep level transient spectroscopy and ascertains that the emissions observed in both techniques have the same origin. The magnitude and continuous shift of the activation energy of the minority carrier emission indicates a distribution of levels in the vicinity of the CdS/CuInSe2 heterointerface. In the case of interface states, the activation energy deduced from admittance spectroscopy corresponds to the position of the electron quasi-Fermi level at the interface, pointing to an inversion of the carrier type at the absorber surface. Measurements with an applied dc bias indicate that the electron Fermi level is pinned at the interface. \#xa9; 1998 American Institute of Physics.
|Journal series||Journal of Applied Physics, ISSN 0021-8979|
|Keywords in English||Annealing, cadmium compounds, CADMIUM SULFIDE SOLAR CELLS, copper compounds, COPPER SELENIDE SOLAR CELLS, crystal defects, Deep level transient spectroscopy, electric admittance, Fermi level, Heterojunctions, hole traps, II-VI semiconductors, indium compounds, INDIUM SELENIDE SOLAR CELLS, Interfaces, interface states, minority carriers, semiconductor heterojunctions, Solar cells, Space charge, ternary semiconductors, thin films, zinc compounds, ZINC OXIDES|
|Publication indicators||: 2006 = 2.316 (2) - 2007=2.38 (5)|
|Citation count*||197 (2015-05-05)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.