Quantitative Phase Fraction Detection in Organic Photovoltaic Materials through EELS Imaging

Polymers

Ondrej Dyck⁴  Sheng Hu⁴  Sanjib Das⁵  Jong Keum¹  Kai Xiao¹  Bamin Khomami⁴  Gerd Duscher²  Christian Nielsen³ 

[1] Center for Nanophase Materials Sciences/Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA;Department of Materials Science and Engineering, University of Tennessee, Knoxville, Knoxville, TN 37996, USA;;Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Knoxville, TN 37996, USADepartment of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Knoxville, TN 37996, USA;Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Knoxville, TN 37996, USA;

关键词: phase detection;    organic photovoltaics;    plasmon energy mapping;    electron energy loss spectroscopy;    EELS Core-loss mapping;    EFTEM;   

DOI  :  10.3390/polym7111523

来源: mdpi

【 摘 要 】

Organic photovoltaic materials have recently seen intense interest from the research community. Improvements in device performance are occurring at an impressive rate; however, visualization of the active layer phase separation still remains a challenge. This paper outlines the application of two electron energy-loss spectroscopic (EELS) imaging techniques that can complement and enhance current phase detection techniques. Specifically, the bulk plasmon peak position, often used to produce contrast between phases in energy filtered transmission electron microscopy (EFTEM), is quantitatively mapped across a sample cross section. A complementary spectrum image capturing the carbon and sulfur core loss edges is compared with the plasmon peak map and found to agree quite well, indicating that carbon and sulfur density differences between the two phases also allows phase discrimination. Additionally, an analytical technique for determining absolute atomic areal density is used to produce an absolute carbon and sulfur areal density map. We show how these maps may be re-interpreted as a phase ratio map, giving quantitative information about the purity of the phases within the junction.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.