CuInSe2 has been targeted as the major photovoltaic material, but the efforts at utilizing its optimum properties have not been extended to n-CuInSe2 due to lack of an appropriate p-type window material. In Phase I, we established the feasibility of fabricating a new n-CuInSe2-based thin film solar cell by using a novel concept of electrochemical surface conversion to p-(CuIn2Se3I)-CuISe3 to form of a n/p heterojunction. The cell performance was primarily determined by the quality of the n-CuInSe2 films and to a lesser extent by the window layer growth parameters. The window layer composition and morphology can be controlled with electrolyte composition. The Phase II effort is aimed at in- depth investigation of the properties n-CuInSe2 and the window layer, the surface conversion mechanism and the opto-electronic properties of the n/p junction. These studies are essential for the development and optimization of the cell components, processing and operation. In addition to processing, cost and environmental advantages, inherent in this simple electrochemical approach to heterojunction formation, several other benefits are anticipated for the title cell over the present p-CuInSe2/n-CdS cell. Optimum lattice match between CuInSe2 and CuIn2Se3I transition layer, low interface state density, higher electron mobility in n-type absorber, improved adhesion to ITO/Glass substrate, greater stability due to similar components (except I) on both sides of the junction should lead to a more efficient and stable solar cell.
