100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films

Abstract

We demonstrate that three Ir͑III͒ complexes used as principal dopants in organic electrophosphorescent diodes have very high photoluminescence quantum efficiency ͑ PL ͒ in a solid-state film. The green emitting complex, fac-tris͑2-phenylpyridinato͒iridium͑III͒ ͓Ir͑ppy͒ 3 ͔, the red-emitting bis͓2-͑2Ј-benzothienyl͒pyridinato-N , C 3 Ј͔ ͑acetylacetonato͒iridium͑III͒ ͓Btp 2 Ir͑acac͔͒, and the blue complex bis͓͑4 , 6-difluorophenyl͒pyridinato-N , C 2 ͔͑picolinato͒iridium͑III͒ ͑FIrpic͒ were prepared as codeposited films of varying concentration with 4,4 Ј-bis͑N-carbazolyl͒-2 , 2 Ј-biphenyl, a commonly used host material. The maximum PL values for Ir͑ppy͒ 3 , Btp 2 Ir͑acac͒, and FIrpic were, respectively, 97% ± 2% ͑at 1.5 mol%͒, 51% ±1% ͑at 1.4 mol%͒, and 78% ± 1% ͑at 15 mol%͒. Furthermore, we also observed that the maximum PL of FIrpic reached 99% ± 1% when doped into the high triplet energy host, m-bis͑N-carbazolyl͒benzene, at an optimal concentration of 1.2 mol%.

Electrically driven photon antibunching from a single molecule at room temperature

“…With a saturated emission intensity of 69,500 cps, 7% of the expected photons are detected that corresponds to the independently determined detection efficiency of the confocal setup (~5%). This result indicates that Ir(piq) 3 possess no intrinsic non-radiative decay channels, as observed, for example, for the red emitting complex Btp 2 Ir(acac) 19 and thereby almost 100% efficiency for triplet emission.…”

“…Instead, to efficiently convert electrical excitation energy into photon emission it is necessary to use a molecule, which is able to trap electron-hole pairs in its T 1 triplet state and to emit photons by phosphorescence. Additional requirements include almost 100% internal quantum efficiencies in solid-state matrices 19 and a short triplet-state lifetime. Examples of such molecular systems include organometallic complexes with a centred heavy metal ion 20 possessing high intersystem crossing probabilities.…”

Enhanced phosphorescence in dibenzophosphole chalcogenide mixed crystal

“…9 To reduce the concentration quenching in organic electronics, a doping technique has been widely applied. 10 However, the number of reports on crystal doping is limited because of the difficulty of preparing doped crystals. 11,12 Thus, in organic optoelectronics it is important to satisfy both high mobility and desired optical property requirements.…”

Highly simplified small molecular phosphorescent organic light emitting devices with a solution-processed single layer

“…[1][2][3][4] Highly efficient PHOLEDs with many different organic layers for charge transport and exciton confinement have been realized and commonly fabricated using a conventional vacuum sublimation technique. [5][6][7] Despite highly efficient for these multi-layer PHOLEDs, their application is still limited by a complex fabrication process due to unavoidable high vacuum conditions.…”