Molecular Understanding of the Chemical Stability of Organic Materials for OLEDs: A Comparative Study on Sulfonyl, Phosphine-Oxide, and Carbonyl-Containing Host Materials

• Published in: Journal of physical chemistry. C Vol. 118; no. 14; pp. 7569 - 7578
• Main Authors: Lin, Na, Qiao, Juan, Duan, Lian, Wang, Liduo, Qiu, Yong
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10.04.2014
• DOI: 10.1021/jp412614k
• ISSN: 1932-7447

Chemical stability of organic materials on service toward excitons and charge carriers is intrinsically associated with the operational stability and economics of state-of-the-art organic light-emitting devices. Here we conducted comprehensive experiments and theoretical calculations to comparatively investigate the intrinsic chemical stability of organic materials, which contain typical electron-accepting moieties of sulfonyl, phosphine-oxide, and carbonyl group. The materials with a diphenylsulfonyl moiety suffered a fatal chemical instability originating from the cleavage of C–S single bond whether under UV irradiation or in electrical-stressed devices. The material with a dibenzothiophene-S,S-dioxide moiety exhibited significantly improved chemical stability because of effective shielding of the weak C–S single bond in a ring. In contrast, the commercially used carbonyl-containing compound demonstrated the highest chemical stability with negligible degradation under the same condition. Quantum chemical calculations fully supported the experimental results and suggested that the bond strength of the weak chemical bonds of the molecules would determine the intrinsic chemical stability of the organic materials in their excited and charged states, which might be a plausible origin of the limited stability of high-energy blue-emitting materials and devices. Several implications have been drawn for the design of new blue-emitting materials.