Preferred Orientation, Grain Sizes and Grain Boundaries of Chalcopyrite-Type Thin Films

Abstract

AbstractChalcopyrite-type thin films - CuInS2, CuInSe2, CuGaSe2, and Cu(In,Ga)Se2 - in various completed solar cells were studied in cross-section by means of electron-backscatter diffraction (EBSD). Valuable information on grain sizes, local grain orientations, film textures, and grain boundaries were extracted from the EBSD linescans and maps. The grain-size distributions from the chalcopyrite-type thin films can be represented well by lognormal distribution functions. The EBSD measurements on CuGaSe2 thin film reveal a <110> fiber texture, in good agreement with x-ray diffraction texture analysis performed on the same sample. The EBSD maps from all samples studied exhibit considerable twinning in the chalcopyrite-type thin films. Indeed, the most frequent types of grain boundaries in these thin films are (near) Σ3 60°-<221> and 71°-<110> twins. It is shown that rotational 180°-<221> twins (which are symmetrically equivalent to 71°-<110>) are more frequently found than anion- or cation-terminated 60°-<221> twin boundaries.