GOALI: Structure and Electronic Properties of Grain Boundaries in Earth Abundant Cu2ZnSnSxSe4-x (CZTS) Thin Film Solar Cells

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

PI: Shenoy, Vivek Proposal Number: 1235870 Institution: Brown University Title: GOALI: Structure and Electronic Properties of Grain Boundaries in Earth Abundant Cu2ZnSnSxSe4-x (CZTS) Thin Film Solar Cells Low-cost, high-throughput, and reliable photovoltaic production methods are needed in order to make solar energy widely available. Thin-film solar cell materials are of particular interest because they can be fabricated in a cost- effective manner. Cu2ZnSnSxSe4-x (CZTS) is regarded as one of the promising candidates of the absorber layer used in thin film devices because of the use of Zn and Sn, two low-cost and earth-abundant elements. The performance is affected by the grain boundaries in the crystalline components. Currently there is no systematic experimental data or theoretical models on the structure and orientation distribution of grain boundaries in CZTS. The PIs will use a multi-scale approach that combines experimental techniques for the grain boundary characterization with first-principles calculations and genetic algorithms for structure determination and kinetic Monte Carlo and molecular dynamics simulations for modeling segregation kinetics. IBM High Resolution Transmission Electron microscopy (HRTEM) will be used to identify the grain boundary orientation by comparing with the TEM images simulated by using density functional calculations. The Electron BackScatter Diffraction (EBSD) method will be employed to measure the distribution of grain boundary as a function of orientation. Spectroscopy (EDS) in the Scanning Transmission Electron Microscopy (STEM) mode can provide information about the atomic composition near grain boundary (Cu rich/poor). The project will provide an opportunity for graduate and undergraduate students to both carry out experimental work in a leading industrial lab and to develop advanced computational skills. The progress made in the computational methods will be included in the course that the PI has created to promote hands-on simulation experience. The project will provide interactive software modules from these projects to K-12 teachers and students participating in Brown?s summer high school. Finally, given the large effort and resources that are being invested in the development of efficient methods to improve the conversion efficiency of CZTS-based solar cells, insights gained from increased atomic level understanding of grain boundaries could have economic impact, particularly in the semiconductor and photovoltaic energy industry.