TY - JOUR
T1 - Efficient triplet application in exciplex delayed-fluorescence OLEDs using a reverse intersystem crossing mechanism based on a Δ e S-T of around zero
AU - Zhang, Tianyou
AU - Chu, Bei
AU - Li, Wenlian
AU - Su, Zisheng
AU - Peng, Qi Ming
AU - Zhao, Bo
AU - Luo, Yongshi
AU - Jin, Fangming
AU - Yan, Xingwu
AU - Gao, Yuan
AU - Wu, Hairuo
AU - Zhang, Feng
AU - Fan, Di
AU - Wang, Junbo
PY - 2014/8/13
Y1 - 2014/8/13
N2 - We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4′,4-tris[3-methylphenyl(phenyl) aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm2 was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process.
AB - We demonstrate highly efficient exciplex delayed-fluorescence organic light-emitting diodes (OLEDs) in which 4,4′,4-tris[3-methylphenyl(phenyl) aminotriphenylamine (m-MTDATA) and 4,7-diphenyl-1,10-phenanthroline (Bphen) were selected as donor and acceptor components, respectively. Our m-MTDATA:Bphen exciplex electroluminescence (EL) mechanism is based on reverse intersystem crossing (RISC) from the triplet to singlet excited states. As a result, an external quantum efficiency (EQE) of 7.79% at 10 mA/cm2 was observed, which increases by 3.2 and 1.5 times over that reported in Nat. Photonics 2012, 6, 253 and Appl. Phys. Lett. 2012, 101, 023306, respectively. The high EQE would be attributed to a very easy RISC process because the energy difference between the singlet and triplet excited states is almost around zero. The verdict was proven by photoluminescence (PL) rate analysis at different temperatures and time-resolved spectral analysis. Besides, the study of the transient PL process indicates that the presence of an unbalanced charge in exciplex EL devices is responsible for the low EQE and high-efficiency roll-off. When the exciplex devices were placed in a 100 mT magnetic field, the permanently positive magnetoelectroluminescence and magnetoconductivity were observed. The magnetic properties confirm that the efficient exciplex EL only originates from delayed fluorescence via RISC processes but is not related to the triplet-triplet annihilation process.
KW - delayed fluorescence
KW - efficient triplet application
KW - exciplex OLED
KW - reverse intersystem crossing
UR - http://www.scopus.com/inward/record.url?scp=84906253208&partnerID=8YFLogxK
U2 - 10.1021/am501164s
DO - 10.1021/am501164s
M3 - 文章
AN - SCOPUS:84906253208
SN - 1944-8244
VL - 6
SP - 11907
EP - 11914
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 15
ER -