Degradation of the materials in organic light-emitting devices (OLEDs) is the major impediment for the development of economically feasible, highly efficient and durable devices for commercial applications. Even though this chemical degradation is complex and the least understood of the different degradation modes in OLEDs, scientists were successful in providing insight into some of the responsible processes. In this progress report we will review recent advances in the elucidation of chemical degradation mechanisms: First possible reasons for defect formation and the most common and important methods to investigate those processes are covered before discussing the reactions and their products for the different types of materials present in a device. We summarize commonalities in the occurring mechanisms, and identify structural features and moieties that can be detrimental to operational stability. Some of the resulting implications on the development of new materials are presented and backed by concrete examples from literature.

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SummaryThe photodegradation behavior of four well-established iridium emitters was investigated. Irradiation of the samples in different solvents and under atmospheric as well as inert conditions helped to identify several pathways that can contribute to the deterioration of these compounds. Degradation via singlet oxygen or the excited states of the emitters as well as the detrimental influence of halogenated solvents are discussed for the different investigated iridium complexes. Some of the resulting degradation products could be identified by using LC–MS or other analytical techniques. The results show how even small structural changes can have a huge influence on rate and mechanism of the photodegradation. The observations from this study may help to better understand degradation processes occurring during the handling of the materials, but also during device processing and operation.

This work reports the combinatorial synthesis and screening of phosphorescent iridium complexes as solution processable emitters for OLEDs. The approach taken here allows for the rapid synthesis, isolation, spectroscopic characterization and identifi cation of the libraries based on chromatographic methods. Subsequent analysis of the irradiation induced degradation provides insight on the stability of the complexes under continuous excitation. The method is versatile and can easily be applied to other metal complexes or organic dyes for various applications, e.g., in electroluminescence, photovoltaics and sensing.

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