Analysis of organic multilayered samples for optoelectronic devices by (low‐energy) dynamic SIMS

Abstract

aThe increasing sophistication of optoelectronic devices requires molecular-level dimensional control in the fabrication of multilayered structures with specifically engineered interfaces. However, the effectiveness of growth and doping strategies devised to achieve the desired device structures often remains unverified due to the lack of adequate characterization techniques. This is particularly true for devices based on conjugated organic compounds, which find increasing use in energy applications (e.g. organic light emitting diodes and organic photovoltaic cells, etc.). The buried interfaces are simply inaccessible or suffer damage when using conventional characterization techniques. In a current project, we address this challenge by advancing the development of low-energy (LE) SIMS for the analysis of organic-based optoelectronic materials systems.In the present study, multilayered organic thin films have been analyzed, varying experimental conditions such as the impact energies for Cs + bombardment in the MCs x + and M − mode on a Cameca Sc-Ultra instrument to investigate the ionization mechanisms as well as the atomic mixing at the interfaces between layers, and the degradation of the organic information. Low-energy dynamic SIMS proved to be a reliable tool for the characterization of organic multilayered optoelectronic devices: MCs x + secondary ions provide information about the distribution of elements within the samples, while negative fragments that are characteristic for the different molecules give information about the structure.

Morphology characterization in organic and hybrid solar cells

“…SIMS has been employed in a number of OPV [259][260][261][262][263][264][265] and hybrid PV 266 morphology experiments. Krebs et al have reported extensively on the analysis of degradation mechanisms in OPVs, which were among the first studies to clearly demonstrate that oxygen and water enter devices via diffusion from the atmosphere through the top (aluminum) electrode.…”

Silver Diffusion in Organic Optoelectronic Devices: Deposition-Related Processes versus Secondary Ion Mass Spectrometry Analysis Artifacts

“…Under low-energy Cs + bombardment, the fragmentation is less prevalent than for kiloelectronvolt bombardment, 13,14 and stable secondary ion intensities of small characteristic fragments are obtained under steady-state conditions. 15 The successful depth profiling of metal−organic multilayered samples 16 and the ability to extract information on the interface morphology 17 have been reported previously. This includes the control of roughness formation for the experimental conditions used 18,19 and of Cs−O nanodot formation in the areas irradiated by a Cs + primary ion beam 20 due to the high mobility of cesium.…”

“…21 Depth profiles presented in previous work also show high Ag secondary ion intensities inside the organic layer. 16,17 Other authors have already encountered this problem. Fostiropoulos et al investigated the metal diffusion into organic films by SIMS by comparing the depth profiles from an Ag/Mg/CuPc:C 60 device with and without lifting off the Ag/Mg cathode.…”

Low-energy oxygen bombardment of silicon by MD simulations making use of a reactive force field

“…Additionally, MD simulations are able to provide information which is complementary to the experimental results obtained in our group on the enhancement of secondary ion emission under Cs + 0168-583X/$ -see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2010.12.059 bombardment combined with simultaneous Cs 0 deposition [23][24][25][26] or the fragmentation of organic molecules [27,28]. For the MD simulations, we will use the force field developed by Kieffer et al which has already been applied successfully, for example, to the study of phase transitions in cristobalite [1,[29][30][31] and B 2 O 3 [2,32].…”