| A novel method for Cu(In,Ga)Se;The compositional, structural, and morphological evolution of the films are examined by scanning electron microscopy, atomic force microscopy, transmission electron microscopy, X-ray diffraction microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and electron probe microanalysis. Using these analyses, a model is developed describing growth by this method. Stages in the growth are: (1) formation of a smooth and dense (In,Ga);By growing films where the relative concentrations of Ga and In vary through the film depth, graded band-gap structures are formed. The growth model explains the spontaneous formation of a low-Ga surface region during the second stage. Methods for engineering different graded structures are also demonstrated. Device performance is analysed for different graded structures, both experimentally and through computer simulation of device performance. The best structure is one with a high band gap near the junction, a lower band gap further in, and an increasing band gap toward the back contact. |
