TY - JOUR
T1 - Intramolecular charge transfer-based spirobifluorene-coupled heteroaromatic moieties as efficient hole transport layer and host in phosphorescent organic light-emitting diodes
AU - Jesuraj, P. Justin
AU - Somasundaram, Sivaraman
AU - Kamaraj, Eswaran
AU - Hafeez, Hassan
AU - Lee, Changmin
AU - Kim, Donghyun
AU - Won, Sang Hee
AU - Shin, Sung Tae
AU - Song, Myungkwan
AU - Kim, Chang Su
AU - Park, Sanghyuk
AU - Ryu, Seung Yoon
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/10
Y1 - 2020/10
N2 - In this study, we report two efficient intramolecular charge transfer (ICT) compounds with versatile functionality as hole transporting layers (HTL) and hosts in emission layer (EML) of phosphorescent organic light emitting diodes (Ph-OLEDs) with donor-acceptor-donor structures. In both molecules, 9,9′-spirobifluorene (SBF) was employed as a common electron acceptor, while phenoxazine (PXZ) or phenothiazine (PTZ) were used as donors. The molecules 2,7-di(10H-phenoxazin-10-yl)-9,9′-spirobi[fluorene] (SBF-PXZ) and 2,7-di(10H-phenothiazin-10-yl)-9,9′-spirobi[fluorene] (SBF-PTZ) were synthesized via a Buckwald-Hartwig cross-coupling reaction in a single step that exhibited typical ICT phenomena. The extremely twisted geometrical configurations of SBF-PXZ and SBF-PTZ may allow for effective intramolecular charge-transfer. Both molecules exhibited strong absorption and emission characteristics in the visible region in solution as well as in the thin film form; significant positive solvatochromism was also observed for both compounds. The replacement of PTZ donor with the PXZ donor caused a bandgap reduction together with an improved ionization potential (IP). The deeper IP (>5.1 eV), greater glass transition temperature, and higher hole mobility extracted from the hole only devices of both molecules revealed them as superior candidates for HTL applications (with/without exciton blocking layers) in Ph-OLEDs. It is further corroborated by the enhanced half-life time of Ph-OLEDs with SBF-PXZ/SBF-PTZ HTLs. Moreover, the OLED performances with SBF-PTZ and SBF-PXZ as EMLs and hosts for phosphorescent dopant OLEDs have exemplified the versatility of the proposed ICT compounds.
AB - In this study, we report two efficient intramolecular charge transfer (ICT) compounds with versatile functionality as hole transporting layers (HTL) and hosts in emission layer (EML) of phosphorescent organic light emitting diodes (Ph-OLEDs) with donor-acceptor-donor structures. In both molecules, 9,9′-spirobifluorene (SBF) was employed as a common electron acceptor, while phenoxazine (PXZ) or phenothiazine (PTZ) were used as donors. The molecules 2,7-di(10H-phenoxazin-10-yl)-9,9′-spirobi[fluorene] (SBF-PXZ) and 2,7-di(10H-phenothiazin-10-yl)-9,9′-spirobi[fluorene] (SBF-PTZ) were synthesized via a Buckwald-Hartwig cross-coupling reaction in a single step that exhibited typical ICT phenomena. The extremely twisted geometrical configurations of SBF-PXZ and SBF-PTZ may allow for effective intramolecular charge-transfer. Both molecules exhibited strong absorption and emission characteristics in the visible region in solution as well as in the thin film form; significant positive solvatochromism was also observed for both compounds. The replacement of PTZ donor with the PXZ donor caused a bandgap reduction together with an improved ionization potential (IP). The deeper IP (>5.1 eV), greater glass transition temperature, and higher hole mobility extracted from the hole only devices of both molecules revealed them as superior candidates for HTL applications (with/without exciton blocking layers) in Ph-OLEDs. It is further corroborated by the enhanced half-life time of Ph-OLEDs with SBF-PXZ/SBF-PTZ HTLs. Moreover, the OLED performances with SBF-PTZ and SBF-PXZ as EMLs and hosts for phosphorescent dopant OLEDs have exemplified the versatility of the proposed ICT compounds.
KW - 2,7-di(10H-phenothiazin-10-yl)-9,9'-spirobi[fluorene] (SBF-PTZ)
KW - 2,7-di(10H-phenoxazin-10-yl)-9,9'-spirobi[fluorene] (SBF-PXZ)
KW - Donor-acceptor (D-A) compounds
KW - Hole transporting layers, (HTL)
KW - Intramolecular charge transfer (ICT) compounds
KW - Phosphorescent organic light emitting diodes (Ph-OLEDs)
UR - http://www.scopus.com/inward/record.url?scp=85086501687&partnerID=8YFLogxK
U2 - 10.1016/j.orgel.2020.105825
DO - 10.1016/j.orgel.2020.105825
M3 - Article
AN - SCOPUS:85086501687
SN - 1566-1199
VL - 85
JO - Organic Electronics
JF - Organic Electronics
M1 - 105825
ER -