Paper EN+AS-ThA4
XPS Characterization of Organic Gradients in Organic Photovoltaic and Organic Light Emitting Devices Using Ar GCIB Depth Profiling

Thursday, November 1, 2012, 3:00 pm, Room 15

The use of organic materials for electronic applications such as Organic Photovoltaics (OPV’s) and Organic Light Emitting Diodes (OLED’s) is rapidly growing. The efficiencies of these devices are widely recognized to depend on the molecular gradients fabricated into the devices. Conversely, the degradation of these devices is suspected to depend on several factors including chemical degradation and chemical migration as a function of use. It is therefore very desirable to develop analytical techniques which can quantify chemical gradients as well as identify degradation products in these films.

Gas Cluster Ion Beam (GCIB) sources with low energy per atom Ar_2,000⁺ ions have recently been demonstrated to provide a depth profiling technique for molecular species (1,2). GCIB depth profiling in an interleaved mode with the surface analysis spectroscopy of X-ray Photoelectron Spectroscopy (XPS) has been applied to model OPV and OLED devices. The 2 to 5 nm information depth of XPS, combined with the demonstrated “non-destructive” chemical information revealed after each GICIB sputter interval, facilitates the chemical gradient analysis of a series of model samples up to several 100 nm in depth with molecular depth resolution < 10 nm.

Selected model OPV and OLED samples were exposed to annealing and environmental degradation testing. The XPS depth profiles measured the migration of organic components and dopants as a function of fabrication processes. This presentation will provide an overview of GICB depth profiling with XPS as well as discuss the insights into efficiencies and degradation processes elucidated by this chemical gradient analysis technique.

1. T. Miyayama, et al. Surf. Interface. Anal. 42 (2010) 1453-1457.

2. T. Miyayama, et al. J. Vac. Sci. Technology A, 28 (2) (2010) L1-L4.