Revisiting Carbazole: Origin, Impurity, and Properties

Abstract

Photoluminescence quantum yield (PLQY) is one of the most important characteristics for organic luminescent materials. However, when carbazole prepared from the lab was compared to that from a commercial source, a remarkable change of PLQY was observed to vary from 37.1% to 69.8%. Taking 9-(4-bromo­benzyl)-9H-carbazole (CzBBr) as an example of carbazole derivatives, the PLQYs of CzBBr synthesized from different origins of carbazole were varied from 16.0% to 91.1%. Our studies demonstrated that efficient radiative transition pathways were activated for commercial carbazole based luminescence, leading to a large enhancement in PLQY with fluorescence (from 16.0% to 54.4%) and phosphorescence (from <1% to 36.7%) for CzBBr. These results suggest that the origin of carbazole plays a very important role in determining the optical properties of carbazole derivatives, alerting us to carefully revisit carbazole and its derivatives, especially those with record-high efficiency.

More than Carbazole Derivatives Activate Room Temperature Ultralong Organic Phosphorescence of Benzoindole Derivatives

“…Our experimental results agreed well with Liu's report. [ 1c,9 ] Differently, the typical ultralong phosphorescence bands at 552, 604, and 661 nm were the intrinsic phosphorescence of Bd derivatives’ radical cations, and 2CzBr activated their intrinsic ultralong phosphorescence probably by the heterojunction. The formation of heterojunction required close proximity of matrix and dopant for easy electron communication to accelerate in generating and stabilizing Bd derivatives’ radical cations.…”

“…Interestingly, Liu et al recently reported their findings that the commercially available carbazole was inevitably mixed with trace carbazole isomer (1H‐benzo[f]indole, Bd), and Bd was believed to be involved in the origination of UOP. [ 1c,9 ] They suggested that Cz and Bd moieties in close proximity acted as a microplanar heterojunction to generate photo‐induced charge‐separated states, and further to produce intense UOP. Based on their results, the UOP of carbazole derivatives previously presented in the literature are actually integrated luminescent properties of carbazole derivatives and Bd's counterparts.…”

Modulating Tri‐Mode Emission for Single‐Component White Organic Afterglow

“…To clarify the effects of trace amounts of carbazole isomers,w ea lso synthesized carbazole from 2-nitro-1,1'biphenyl to prepare Lab-CzBH and Lab-CzBMe. [51] Indeed, poor afterglow performances of Lab-CzBH and Lab-CzBMe were observed by the naked eye (Figure S28). But, the trimode emission can be still observed when the delay time is less than 5ms( Figure S29).…”

Structurally Resemblant Dopants Enhance Organic Room‐Temperature Phosphorescence

“…[19] Further research demonstrated that dopant doping is very effective in realizing high quantum yield, long-lived phosphorescent, and fluorescent organic materials. [31] Dibenzothiophene (DBT), a heterocyclic aromatic compound that is similar to Cz with its central pyrrole ring substituted by a thiophene ring, is an electron-donating moiety with good hole-transporting ability and high triplet energy, which was reported to be a phosphor exhibiting weak RTP in the crystal state. [4] DBT has been derivatized into various compounds exhibiting excellent performance in their respective fields, such as 2,8-bis(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) which is well applied as a highly efficient host material in OLED device, [16] and dibenzo[b,d]thiophen-2-yl(phenyl) methanone (BDBT) derivatives that are reported as promising Doping has shown very promising potential in endowing room-temperature phosphorescence (RTP) properties of organic phosphors with minimal effort.…”

“…[ 19 ] Further research demonstrated that dopant doping is very effective in realizing high quantum yield, long‐lived phosphorescent, and fluorescent organic materials. [ 31 ]…”