Persistent Photoconductivity in n- and p-Type CuGaSe sub 2
07 January 2001
Persistent photoconductivity (PPC) is observed in p-type and n-type (Ge,Zn co-doped) CuGaSe sub 2 (CGS) single crystals up to 270 K. The time dependence of the photoconductivity can be described by a stretched exponential decay. In the case of n-type CGS an increase of the charge carrier mobility as well as the carrier concentration is observed upon illumination, whereas PPC in p-CGS is only related to an increase of the hole density. The origin of the PPC is discussed with respect to metastable defects and defect interactions. In addition, the influence of such metastabilities and deep defects on solar cell performance and doping limits of the material are examined.