Stable radical cores: a key for bipolar charge transport in glass forming carbazole and indole derivatives

Abstract

Stable radical adducts of the TTM series bearing carbazolyl or indolyl fragments show bipolar transport properties with mobility values among the highest detected in glassy small molecules. Bipolarity is attributed to the radical character, while the heterocyclic ring confers the adducts the glassy morphological states and the non-dispersive regimes for charge transport.

Stable All‐Organic Radicals with Ambipolar Charge Transport

“…Bromo‐substituted radical adduct 1 exhibits the highest electron mobility value of 1.7×10 −2 cm 2 V −1 s −1 at an electric field of 0.64×10 6 V cm −1 of the entire series without losing its hole‐transport properties. Taking into account that carbazole‐based compounds have been usually defined as hole‐transport materials, the electron transport determined for the radical adduct Cbz‐TTM and the series of derivatives here studied, should be related to the presence of the radical TTM fragment, which is easily and reversibly reduced . Accordingly, the introduction of electron‐withdrawing groups on the carbazole core should influence the transporting properties of both positive and negative charges.…”

“…The parent compound Cbz‐TTM exhibited relatively high hole and electron mobilities of 4.6×10 −4 and 4.7×10 −3 cm 2 V −1 s −1 , respectively . To explore the charge‐transport properties of this series of compounds, thin films of radicals 1 – 4 were subjected to the measurements by the xerographic time‐of‐flight (XTOF) technique.…”

“…[a] Values taken from ref. . Layer prepared by casting a THF solution of the pure radical adduct Cbz‐TTM.…”

Persistent Borafluorene Radicals

“…[11] Moreover, redox-active radicals are beneficial as they may perform in an ambipolar fashion, being susceptible to both oxidation or reduction processes. [12] However, many radicals are short-lived, and thus the development of stable materials-relevant radical compounds that are well-poised for synthetic elaboration still presents a major challenge for the scientific community. Boron-centered radicals have been studied extensively in recent years because of their importance in both pure and applied chemistry.…”

Heteroleptic iridium (III) complexes with three different ligands: Unusual triplet emitters for light-emitting electrochemical cells

“…These different assignments are consistent with the DFT calculations done on the two complexes. On the basis of the onset potentials of oxidation and reduction, HOMO and LUMO energy levels of [Ir(dfppy)(tpy)(bpy)](PF 6 ) and [Ir(dfppy)(tpy)(phen)](PF 6 ) could be estimated with regard to the energy level of ferrocene (4.8 eV below vacuum) and determined as being 5.51 eV and 5.56 eV for the HOMO levels and 3.20 eV and 3.18 eV for the LUMO levels respectively (see Table 1) [66,67].…”