Energy level alignment at a charge generation interface between 4,4′-bis(N-phenyl-1-naphthylamino)biphenyl and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile

Abstract

We have determined the electronic energy level alignment at the interface between 4,4′-bis(N-phenyl-1-naphthylamino)biphenyl (NPB) and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) using ultraviolet photoelectron spectroscopy. The highest occupied molecular orbital (HOMO) of 20 nm thick HAT-CN film was located at 3.8 eV below the Fermi level. Thus the lowest unoccupied molecular orbital (LUMO) is very close to the Fermi level. The HOMO position of NPB was only about 0.3 eV below Fermi level at NPB/HAT-CN interface. This enables an easy excitation of electrons from the NPB HOMO to the HAT-CN LUMO, creating electron-hole pairs across this organic-organic interface.

Technical issues in graphene anode organic light emitting diodes

“…The hole injection barriers (ϕ h s) were estimated using the energy difference between the Fermi level (E f ) and the onset of HOMO peak. Details of the UPS methods in studying organic interfaces can be found elsewhere [10]. The ϕ h s of MLG/TAPC and MLG/Hat-CN/TAPC were 0.65 eV and 3.03 eV, respectively.…”

“…In the optical part, we discuss microcavity and contrast its role to that of ITO anode case [8,9]. In the interfacial consideration, we compare the energy alignments of ITO and graphene with respect to adjacent organic layer, hole transport layer (HTL), and discuss a strategy which is useful in improving the hole transport [10,11]. In the patterning part, we investigate the patterning issue of graphene films [12].…”

Inhibition of solution-processed 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile crystallization by mixing additives for hole injection layers in organic light-emitting devices

“…Here, we used the averages of the reported energy level values for HAT-CN. 30,31 The electroluminescence spectra, current density-voltage-luminance, current density-external quantum efficiency and current density-power efficiency characteristics are shown in Figure 4. Device B-1 showed a significantly lower driving voltage than device B-2.…”

“…Electron affinity (EA) values ranging from 5.7 to 6.1 eV have been reported. [30][31] In OLEDs, HAT-CN is usually adjacently arranged to the hole transporting materials (HTMs) such as 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl (α-NPD). When applying an electric field to the HAT-CN/ HTM bilayer, an electron is injected from the highest occupied molecular orbital of HTM to the lowest unoccupied molecular orbital of HAT-CN, thereby generating electron/hole charge pairs at the interface, with HTM functioning as an electron donor material and HAT-CN functioning as an electron acceptor material.…”

Efficient Green Phosphorescent OLEDs with Hexaazatrinaphthylene Derivatives as a Hole Injection Layer

“…이러한 HIL의 정공주입 메커니즘은 HIL과 HTL 층간의 계면 에서의 전하의 분리 및 HTL의 HOMO 에너지 준위로의 정공 이송, HIL의 LUMO 에너지 준위로의 전자 이송의 단계를 거치는 것으로 이 해되고 있다 [8][9]. 이러한 새로운 개념의 정공 주입 메커니즘은 HIL과 전극 일함수 사이의 정공 주입장벽을 극복하여 주입되는 기존의 field-assisted thermionic charge injection 메커니즘과는 다른 방식의 정공 주입을 가능하게 하였다 [10][11]. 하지만 음극으로부터 주입되는 전자와 정공이 균형된 비율을 이루기 위해서는 이러한 HIL들이 다양 …”