Fundamental Studies of the Effect of Crystal Defects on CuInSe2/CdS Heterojunction Behavior: Final Report, 28 June 1993--30 June 1998

This report describes the work performed by the University of Illinois at Urbana-Champaign. The following results were obtained under the work funded by this subcontract. ; Point defects and electronic properties of Cu(In1-xGax)Se2: *New record results for hole mobilities in Cu(In1-xGax)Se2 based on single crystals grown by Rockett's group. *Demonstrated the role of Ga in determining holeconcentrations. Showed that Ga does not affect the hole mobility in this material and why this is the case. Determined the diffusion coefficient for Ga in single-crystal Cu(In1-xGax)Se2. *Demonstrated the structure and optoelectronic properties of the CuIn3Se5 ordered-defect phase of CuInSe2. *Characterized the detailed effects of Na on Cu(In1-xGax)Se2 solar cells and on the fundamentalproperties of the material itself (reduces compensating donors in p-type materials). *In collaboration with groups at the Universities of Salford and Liverpool in the United Kingdom, studied the effect of ion implantation damage on Cu(In1-xGax)Se2 single-crystals. Materials for and characterization of devices: *Developed a novel contact metallurgy that improves adhesion to the underlying Moback-contact in solar cells made with Cu(In1-xGax)Se2. This material has also yielded substantial novel materials science behaviors, including grain rotation and growth prior to phase separation in a metastable binary alloy. *Characterized the electroluminescence as a function of temperature and Ga content in Cu(In1-xGax)Se2 solar cells and showed that the radiative recombination pathways arenot band-to-band as in normal semiconductors, but rather, proceed through defect states. *Working with a group at the University of Uppsala in Sweden, demonstrated novel aspects of the bonding and chemistry of dip-coated CdS heterojunction materials used as heterojunction partner materials in Cu(In1-xGax)Se2 solar cells.