Admittance measurements on CIGS solar cells

Thin film solar cells based on polycrystalline CIGS absorbers are one of the most promising candidates for the low-cost and efficient large-scale solar energy conversion devices. Electronic transport properties of ZnO/CdS/Cu(In,Ga)Se₂ solar cells were investigated by means of admittance measurements in a frequency range from 600 Hz to 1 MHz and a temperature range from 80 to 300 K. Dependent on the sample under investigation, one characteristic frequency (inflection point) corresponding to an activation energy between 80 and 160 meV or two points corresponding to an activation energy about 400 meV have been observed. Analysis of the measured frequencies and obtained activation energies provides information on the equilibrium Fermi level position at the CdS/CIGS interface.