High Spatial Resolution Laser Desorption/Ionization Mass SpectrometryImaging of Organic Layers in an Organic Light-Emitting Diode

摘要

To improve the durability of organic materials in electronic devices, an analytical method that can obtain information about the molecular structure directly from specific areas on a device is desired. For this purpose, laser desorption/ionization mass spectrometry imaging (LDI-MSI) is one of the most promising methods. The high spatial resolution stigmatic LDI-MSI with MULTUM-IMG2 in the direct analysis of organic light-emitting diodes was shown to obtain a detailed mass image of organic material in the degraded area after air exposure. The mass image was observed to have a noticeably improved spatial resolution over typical X-ray photoelectron spectroscopy, generally used technique in analysis of electronic devices. A prospective m/z was successfully deduced from the high spatial resolution MSI data. Additionally, mass resolution and accuracy using a spiral-orbit TOF mass spectrometer, SpiralTOF, were also investigated. The monoisotopic mass for the main component, N,N′-di-1-naphthalenyl-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (m/z 588), was measured with a mass resolution of approximately 80,000 and a mass error of about 5 mDa using an external calibrant. This high mass resolution and accuracy data successfully deduced a possible elementalcomposition of partially remained material in the degraded area,C36H24, which was determined as anthracene,9-[1,1′-biphenyl]-4-yl-10-(2-naphthalenyl) by combining structural information withhigh-energy CID data. The high spatial resolution of 1 μm in LDI-MSI along with highmass resolution and accuracy could be useful in obtaining molecular structureinformation directly from specific areas on a device, and is expected to contributeto the evolution of electrical device durability.