Preparation of cadmium- free buffer layers f or CIGS solar cells

Abstract

Indium hydroxy sulfide (In(OH)xSy) as a cadmium (Cd)-free buffer layer for CuInGaSe2 (CIGS) solar cells was prepared by the chemical bath deposition (CBD) and the reaction time was optimized. The band gap energy and transmittance data alongside the thickness results from the direct observation with focused ion beam system (FIB) could be a powerful tool for optimizing the conditions. In addition, X-ray diffractometer (XRD), X-ray photoelectron microscopy (XPS), and scanning electron microscope (SEM) were also employed for the layer characterization. The results indicated that the optimum reaction time for In(OH)xSy buffer layer deposition by CBD was 20 min at 70 ℃ under the conditions employed. At the optimum conditions, the buffer layer thickness was near 57 nm and the band gap energy was 2.7 eV. In addition, it was found that there was no XPS peak shift in between the buffer layers deposited on molybdenum (Mo)/glass and that on CIGS layer. © 2014 The Korean Society of Industrial and Engineering Chemistry. All rights reserved.