Abstract Upon exposure to photooxidative conditions, organic materials are susceptible to undergo degradation via processes involving radical oxygen species and/or reaction with singlet oxygen (1O2). In this frame, the work herein presents a new and straightforward methodology to clarify the role of highly-reactive 1O2 in the photodegradation mechanism of conjugated materials applied in organic electronics. The general methodology consists in the comparison of the infrared signatures of the conjugated materials after the materials are exposed to photooxidative and thermooxidative conditions and in situ generated 1O2. The methodology was validated by analysing the behaviour of four donor materials commonly used in organic solar cells. Analysis of the degradation mechanism of these materials allowed exemplifying the three possible case scenarios, namely (1) both 1O2 and radical oxygen species are involved in the general photooxidation mechanism of the studied material, (2) the material is unreactive towards 1O2 and thus this species plays no role in the photooxidation process, and (3) the conjugated material is reactive towards chemically produced 1O2 but this species is not the main responsible for the photooxidative degradation of the material. In the latter two cases, a free-radical oxidation process accounts for the photooxidation of the investigated materials. The results derived from this simple, yet enlightening, methodology provide fundamental understanding about the degradation pathways of conjugated materials, which is a key point to develop not only efficient but also stable organic electronic devices.

中文翻译：

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评估单线态氧参与共轭材料光氧化的有效且简单的工具

摘要 在暴露于光氧化条件下时，有机材料容易通过涉及自由基氧物种和/或与单线态氧 (1O2) 反应的过程发生降解。在这个框架中，本文的工作提出了一种新的、直接的方法来阐明高反应性 1O2 在用于有机电子学的共轭材料的光降解机制中的作用。一般方法包括在材料暴露于光氧化和热氧化条件以及原位生成 1O2 后，比较共轭材料的红外特征。该方法通过分析有机太阳能电池中常用的四种供体材料的行为得到验证。分析这些材料的降解机制可以举例说明三种可能的情况，即 (1) 1O2 和自由基氧物种都参与所研究材料的一般光氧化机制，(2) 该材料对 1O2 不反应，因此该物种在光氧化过程中没有作用，以及 (3) 共轭材料对化学产生的 1O2 具有反应性，但该物种不是材料光氧化降解的主要原因。在后两种情况下，自由基氧化过程解释了所研究材料的光氧化。这种简单但具有启发性的方法得出的结果提供了对共轭材料降解途径的基本理解，这是开发高效且稳定的有机电子器件的关键。