TY - JOUR
T1 - Dinuclear Design of a Pt(II) Complex Affording Highly Efficient Red Emission
T2 - Photophysical Properties and Application in Solution-Processible OLEDs
AU - Shafikov, Marsel Z.
AU - Daniels, Ruth
AU - Pander, Piotr
AU - Dias, Fernando B.
AU - Williams, J. A.Gareth
AU - Kozhevnikov, Valery N.
PY - 2019/2/27
Y1 - 2019/2/27
N2 -
The light-emitting efficiency of luminescent materials is invariably compromised on moving to the red and near-infrared regions of the spectrum due to the transfer of electronic excited-state energy into vibrations. We describe how this undesirable "energy gap law" can be sidestepped for phosphorescent organometallic emitters through the design of a molecular emitter that incorporates two platinum(II) centers. The dinuclear cyclometallated complex of a substituted 4,6-bis(2-thienyl)pyrimidine emits very brightly in the red region of the spectrum (λ
max
= 610 nm, φ = 0.85 in deoxygenated CH
2
Cl
2
at 300 K). The lowest-energy absorption band is extraordinarily intense for a cyclometallated metal complex: at λ = 500 nm, ϵ = 53 800 M
-1
cm
-1
. The very high efficiency of emission achieved can be traced to an unusually high rate constant for the T
1
→ S
0
phosphorescence process, allowing it to compete effectively with nonradiative vibrational decay. The high radiative rate constant correlates with an unusually large zero-field splitting of the triplet state, which is estimated to be 40 cm
-1
by means of variable-temperature time-resolved spectroscopy over the range 1.7 < T < 120 K. The compound has been successfully tested as a red phosphor in an organic light-emitting diode prepared by solution processing. The results highlight a potentially attractive way to develop highly efficient red and NIR-emitting devices through the use of multinuclear complexes.
AB -
The light-emitting efficiency of luminescent materials is invariably compromised on moving to the red and near-infrared regions of the spectrum due to the transfer of electronic excited-state energy into vibrations. We describe how this undesirable "energy gap law" can be sidestepped for phosphorescent organometallic emitters through the design of a molecular emitter that incorporates two platinum(II) centers. The dinuclear cyclometallated complex of a substituted 4,6-bis(2-thienyl)pyrimidine emits very brightly in the red region of the spectrum (λ
max
= 610 nm, φ = 0.85 in deoxygenated CH
2
Cl
2
at 300 K). The lowest-energy absorption band is extraordinarily intense for a cyclometallated metal complex: at λ = 500 nm, ϵ = 53 800 M
-1
cm
-1
. The very high efficiency of emission achieved can be traced to an unusually high rate constant for the T
1
→ S
0
phosphorescence process, allowing it to compete effectively with nonradiative vibrational decay. The high radiative rate constant correlates with an unusually large zero-field splitting of the triplet state, which is estimated to be 40 cm
-1
by means of variable-temperature time-resolved spectroscopy over the range 1.7 < T < 120 K. The compound has been successfully tested as a red phosphor in an organic light-emitting diode prepared by solution processing. The results highlight a potentially attractive way to develop highly efficient red and NIR-emitting devices through the use of multinuclear complexes.
KW - deep-red luminescence
KW - dinuclear platinum complex
KW - electroluminescence
KW - near-infrared emission
KW - triplet harvesting
U2 - 10.1021/acsami.8b18928
DO - 10.1021/acsami.8b18928
M3 - Article
AN - SCOPUS:85061934037
VL - 11
SP - 8182
EP - 8193
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
SN - 1944-8244
IS - 8
ER -