Negative Charge Management to Make Fragile Bonds No Longer Fragile towards Electrons for Robust Organic Optoelectronic Materials

Abstract

<p>The development of robust organic (opto)electronic devices is mainly hindered by the chemical deterioration of organic materials on service. For organic light-emitting diode (OLED) materials, a key molecular parameter for intrinsic chemical stability is the bond-dissociation energy of the fragile bond (BDE<sub>f</sub>) with the lowest BDE in the molecule. Although rarely concerned, most OLED molecules have the lowest BDE<sub>f</sub> in negatively charged states (BDE<sub>f</sub>(−), ∼1.6−2.5 eV), which would be a fatal short-slab for device stability. Here, we confirmed the close correlation between BDE<sub>f</sub>(−), intrinsic material stability, and device lifetime. To make fragile bonds no longer fragile towards electrons, we found that introducing strong electron-withdrawing groups with delocalizing structures would be an effective and universal strategy, which was found in typical phosphine-oxide and carbazole module molecules and backed by comparisons in several reported and newly designed molecules. It not only substantially improves BDE<sub>f</sub>(−) by ∼1 eV, but revives the originally vulnerable building blocks, thus largely enriches available groups for rational design of robust OLED and other organic (opto)electronic materials.</p>