Effect of the position of nitrogen in pyridoindole on photophysical properties and device performances of α-, β-, γ-carboline based high triplet energy host materials for deep blue devices

Abstract

Three carboline derivatives with nitrogen at different positions of the pyridoindole unit were synthesized and the effect of the position of nitrogen on the photophysical properties and device performances was investigated. β-Carboline was effective in obtaining high triplet energy and stabilizing energy levels, while α-carboline was better than other carbolines in terms of quantum efficiency. However, γ-carboline could not stabilize the LUMO level and low quantum efficiency was obtained.

Effect of nitrogen position of carboline on the device performances of blue phosphorescent organic light-emitting diodes

“…Several carboline based host materials have been synthesized and could improve the quantum efficiency of blue PHOLEDs due to high triplet energy and bipolar charge transport properties. However, most carboline based host materials were derived from a-carboline [11][12][13] and little research was carried out about the bipolar host materials derived from carboline unit with different nitrogen orientations [10].…”

“…Typically, the hole transport and electron transport units were used in the molecular structure for the bipolar transport properties [1][2][3][4][5][6][7], but bipolar units can also be effectively used as the building unit of the high triplet energy bipolar host materials [8][9][10][11][12][13]. Recently, carboline moieties are being investigated as the bipolar transport type building block of the bipolar host materials [8][9][10][11][12][13]. Several carboline based host materials have been synthesized and could improve the quantum efficiency of blue PHOLEDs due to high triplet energy and bipolar charge transport properties.…”

Synthesis and properties of 5,7‐disubstituted 5,7‐dihydropyrido[2,3‐b:6,5‐b′]diindoles

“…[6][7][8] Besides medical applications, a-carboline derivatives show interesting and promising electronical and photophysical properties and therefore could be used in the field of material science. [10] Due to the diversity of possible applications and the promising properties of carboline derivatives it is not surprising that they have attracted considerable research interest and that they still are subject of current research. [9] In these studies a-carbolines exhibited the best device efficiencies (Figure 1).…”

Bipolar Host Material for Phosphorescent OLEDs Based on 2,7‐Diazacarbazole as a New Electron‐transporting Unit

“…Bipolar characteristics of a host material can be realized by incorporating both hole-and electron-transporting units into the backbone. [7][8][9][10][11] Pyridoindole (carboline) is a stronger electron-withdrawing unit than that of pyridine because two π-electron-deficient C N moieties can improve the electron-transporting abilities and obtain high E T . Backbone structures with aromatic amines such as carbazole have been used to obtain high triplet energies.…”