Title :
Influence of Na and S incorporation on the electronic transport properties of Cu(In,Ga)Se2 solar cells
Author :
Rau, U. ; Schmitt, M. ; Hilburger, D. ; Engelhardt, F. ; Seifert, O. ; Parisi, J. ; Riedl, W. ; Rimmasch, J. ; Karg, F.
Author_Institution :
Phys. Inst., Bayreuth Univ., Germany
Abstract :
The controlled incorporation of Na as well as of S into the absorber material of the Cu(In,Ga)Se2 solar cells leads to an increase of conversion efficiency. We investigate the influence of both ingredients on the electronic transport properties of the cells by means of quantum efficiency and temperature dependent current-voltage measurements, as well as by admittance spectroscopy. We find that the incorporation of Na leads to a shallow acceptor state at about 75 meV above the valence band, thus increasing the free carrier concentration in the absorber material. The benefit of S seems to originate from a passivation of deep trap states rather than from a widening of the band gap due to the formation of a Cu(In,Ga)(Se,S)2 compound
Keywords :
carrier density; copper compounds; electric admittance measurement; electric current measurement; electron-hole recombination; indium compounds; passivation; sodium; solar cells; sulphur; ternary semiconductors; voltage measurement; Cu(In,Ga)Se2 solar cells; Cu(InGa)(SeS)2; Cu(InGa)Se2; Na; Na incorporation; S; S incorporation; absorber material; admittance spectroscopy; band gap widening; conversion efficiency increase; deep trap states passivation; electronic transport properties; free carrier concentration; quantum efficiency measurement; recombination losses reduction; shallow acceptor state; temperature dependent current-voltage measurements; Admittance measurement; Atmosphere; Current measurement; Doping; Glass; Passivation; Photovoltaic cells; Sputtering; Temperature dependence; Temperature measurement;
Conference_Titel :
Photovoltaic Specialists Conference, 1996., Conference Record of the Twenty Fifth IEEE
Conference_Location :
Washington, DC
Print_ISBN :
0-7803-3166-4
DOI :
10.1109/PVSC.1996.564301
