TY - JOUR
T1 - Pyrimidine based hole-blocking materials with high triplet energy and glass transition temperature for blue phosphorescent OLEDs
AU - Jang, Seokhoon
AU - Han, Si Hyun
AU - Lee, Jun Yeob
AU - Lee, Youngu
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/5
Y1 - 2018/5
N2 - We designed and synthesized new hole-blocking materials (HBMs), mPyrPPB and pPPyrPB, consisting of pyrimidine and phenylene segments for high-performance blue phosphorescent OLEDs. The thermal, electrochemical, and optical properties of mPyrPPB and pPPyrPB were systemically investigated. It was found that the Tg values of mPyrPPB and pPPyrPB were 118 and 137 °C, respectively. Especially, the triplet energy and highest occupied molecular orbital (HOMO) energy level of mPyrPPB were 2.77 eV and −6.86 eV, respectively, indicating that it had sufficiently high triplet energy and deep HOMO energy level for the hole-blocking layer (HBL) in blue phosphorescent OLED devices. It was found that all the meta conjugation of mPyrPPB molecular structure effectively prevented π-electron delocalization and thus increased the triplet energy and electron transport property. In addition, mPyrPPB exhibited higher electron-transporting property than pPPyrPB because mPyrPPB possessed effective intermolecular hydrogen bonds. When mPyrPPB was utilized as a HBM for a blue phosphorescent OLED device, external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) values effectively increased to 16.4%, 36.7 cd/A, and 13.4 lm/W, respectively. Compared to the reference device without HBM, EQE, CE, and PE increased by 38%, 35%, and 54% respectively, mainly due to the confinement of triplet excitons and holes and improved electron-transporting ability.
AB - We designed and synthesized new hole-blocking materials (HBMs), mPyrPPB and pPPyrPB, consisting of pyrimidine and phenylene segments for high-performance blue phosphorescent OLEDs. The thermal, electrochemical, and optical properties of mPyrPPB and pPPyrPB were systemically investigated. It was found that the Tg values of mPyrPPB and pPPyrPB were 118 and 137 °C, respectively. Especially, the triplet energy and highest occupied molecular orbital (HOMO) energy level of mPyrPPB were 2.77 eV and −6.86 eV, respectively, indicating that it had sufficiently high triplet energy and deep HOMO energy level for the hole-blocking layer (HBL) in blue phosphorescent OLED devices. It was found that all the meta conjugation of mPyrPPB molecular structure effectively prevented π-electron delocalization and thus increased the triplet energy and electron transport property. In addition, mPyrPPB exhibited higher electron-transporting property than pPPyrPB because mPyrPPB possessed effective intermolecular hydrogen bonds. When mPyrPPB was utilized as a HBM for a blue phosphorescent OLED device, external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) values effectively increased to 16.4%, 36.7 cd/A, and 13.4 lm/W, respectively. Compared to the reference device without HBM, EQE, CE, and PE increased by 38%, 35%, and 54% respectively, mainly due to the confinement of triplet excitons and holes and improved electron-transporting ability.
KW - Glass transition temperature
KW - Hole blocking
KW - OLED
KW - Phosphorescence
KW - Triplet energy
UR - http://www.scopus.com/inward/record.url?scp=85043515876&partnerID=8YFLogxK
U2 - 10.1016/j.synthmet.2018.03.002
DO - 10.1016/j.synthmet.2018.03.002
M3 - Article
AN - SCOPUS:85043515876
SN - 0379-6779
VL - 239
SP - 43
EP - 50
JO - Synthetic Metals
JF - Synthetic Metals
ER -