| AVS 57th International Symposium & Exhibition | |
| Energy Frontiers Topical Conference | Wednesday Sessions |
| Session EN+TF-WeM |
| Session: | CIGS, CZTS and Chalcopyrite Films & Solar Cells |
| Presenter: | W. Li, Weizmann Institute of Science, Israel |
| Authors: | W. Li, Weizmann Institute of Science, Israel S.R. Cohen, Weizmann Institute of Science, Israel K. Gartsman, Weizmann Institute of Science, Israel P. von Huth, Weizmann Institute of Science, Israel R. Popovitch-Biro, Weizmann Institute of Science, Israel Th. Rissom, Helmholtz Zentrum Berlin, Germany D. Cahen, Weizmann Institute of Science, Israel |
| Correspondent: | Click to Email |
CIGS is a promising material for solar cell applications. Uniformity of the polycrystalline composition and structure is an important factor in the solar cell performance. This work is an attempt to study CIGS (non)uniformity systematically as a function of depth, employing independent, complementary high resolution techniques which also reveal inter- and intra-grain compositional, structural, and electronic nonuniformities. In particular, thin cross-sections, prepared by field ion beam (FIB), were studied using TEM-based techniques to achieve higher spatial resolution of the composition than is normally possible. It was found that the Ga/In ratio in the devices drops initially with depth, then rises sharply again near the Mo contact. Furthermore, large variations of this ratio are observed from grain to grain. This variation is even observed within individual single crystal grains along their growth direction. Our measurements confirm the formation of a MoSe2 phase at the Mo – CIGS interface. The lattice constant, measured by selected area diffraction (SAD), varies with the Ga composition, in agreement with Vegard's law. The extent of compositional variation was found to vary inversely with the temperature of sample preparation. Additionally, our measurements confirm the formation of a MoSe2 phase at the Mo – CIGS interface.
A series of scanning probe (SPM)-based techniques, including scanning capacitance microscopy (SCM) and conducting probe atomic force microscopy (CP-AFM) were applied to correlate local device performance and doping concentration with the composiitonal (non)uniformity revealed in these TEM results and will be presented here.
This compositional non-uniformity may well be of relevance for the properties and performance of solar cells made with such films, and this issue will be addressed in the talk.