Microstructural And Microchemical Analysis of Chalcopyrite Cu(In,Ga)Se 2 Films
- PDF / 487,973 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 158 Views
B4.2.1
Microstructural And Microchemical Analysis of Chalcopyrite Cu(In,Ga)Se2 Films Chun-Ming Li, Chang-Hui Lei, Ian M. Robertson, Angus Rockett Department of Materials Science and Engineering University of Illinois at Urbana-Champaign 1304 West Green Street, Urbana, IL 61801, U.S.A. ABSTRACT The microstructure and microchemistry of Cu(In,Ga)Se2 (CIGS) films have been analyzed by means of transmission electron microscopy (TEM). Specimens were obtained from a number of groups producing high-performance solar cells from these materials. Both plan-view and crosssectional TEM samples were prepared by mechanical grinding and ion milling. Twins can be found easily within the films while dislocations are present only in a few grains and with low density. No extended structural defects such as stacking faults were discovered. X-ray energy dispersive spectroscopy was used to study the chemical composition of grains and grain boundaries. Experimental results showed no difference between the composition in the grain interiors and the grain boundary. In addition, there is no obvious enhancement of oxygen and sodium at grain boundaries. Structural depth dependences were also not found. INTRODUCTION As leading candidates for absorber materials in large-area photovoltaic power generation systems, copper indium gallium diselenide (including CuInSe2, CuGaSe2, CuInS2 and so on), abbreviated as CIGS, and related compounds have attracted much interest in developing high performance solar cells. Devices based upon CIGS have achieved the highest performances in both small area cells [1] and large area modules [2, 3]. Nevertheless, several significant problems remain that hamper commercial application. Among them, key elements governing the properties of the solar cells are unknown. This leads to uncertainty in manufacturing, as materials produced by a range of techniques have strikingly different properties and solar cell performances in spite of appearing identical to many common analysis methods. On the other hand, lack of a fundamental understanding of CIGS hampers design of new processes and materials by which even higher performances can be obtained. Issues that need to be resolved include the nanoscale structure and chemistry of the CIGS absorber layer and the surrounding grain boundaries. This paper deals with the microstructural and microchemical analysis of CIGS films provided by different manufacturers. Twins and dislocations were examined while other defects were not found. The chemical concentration of all elements was profiled with both plan-view and crosssectional samples. Comparison was made between grain boundaries and grain interiors for each sample and among different samples. EXPERIMENTAL DETAILS Two kinds of CIGS samples were examined: CIGS deposited on Mo-coated glass provided by Shell Solar Industries (SSI), and CIGS deposited on Mo-coated stainless steel provided by Global Solar Energy (GSE). Aside from the molybdenum between the CIGS and the stainless
Downloaded from https://www.cambridge.org/core. Columbia Uni
Data Loading...
