White Organic Light-Emitting Diodes from Single Emissive Layers: Combining Exciplex Emission with Electromer Emission

Abstract

In this work, white light emission from the blend of a hole transport material, 4,4′-cyclohexylidene bis­[N,N-bis­(4-methylphenyl)­benzenamine] (TAPC), and an electron transport material, 2,2′,2″-(1,3,5-benzinetriyl)-tris­(1-phenyl-1H-benzimidazole) (TPBi), was explored. Organic light-emitting diodes fabricated with the TAPC/TPBi blend as a single emissive layer showed sky blue exciplex emission at low voltages and yellow electromer emission at high voltages. Simultaneous emission of the blue exciplex and yellow electromer can be tuned to obtain pure white light emission. By combining the exciplex emission with field-induced electromer emission, pure white light emission with CIE color coordinates of (0.34, 0.31) was achieved. Transient electroluminescence measurements reveal the nature of the emission species. Electromer emission has significantly long-lived components as compared to the exciplex. The long electroluminescence decay obtained from electromer emission indicates possible utilization of triplet excitons in radiative recombination.

White vertical organic permeable-base light-emitting transistors obtained by mixing of blue exciton and orange interface exciplex emissions

“…As a result, the EL spectra of the blue OPB-LET did not contain any additional band which may, for instance, originate from the TAPC electroplex. 19 The transfer current density versus voltage plots (Fig. 3(b)) show that the blue OPB-LET is not characterized by high current leakages through the base (J EC c J EB ).…”

Biphenylvinylene quinolinol derivatives and their light‐emitting properties

“…It may assure the efficient migration of electrons across the device, yet it may not be able to stop the leakage of holes. To effectively stop the leakage of holes, TPBI (1,3,5‐tris[1‐phenyl‐1H‐benzimidazol‐2‐yl]benzene) with a substantially lower HOMO level was considered to be an alternate electron transporter in the fabrication of OLED devices 20 …”

“…It is known that TPBI can act as a better hole blocker than AlQ 3 20 . The LUMO level of TPBI is lower than AlQ 3 , therefore can effectively stop the holes to move across the junction (Figure 4).…”

“…To effectively stop the leakage of holes, TPBI (1,3,5-tris[1-phenyl-1H-benzimidazol-2-yl]benzene) with a substantially lower HOMO level was considered to be an alternate electron transporter in the fabrication of OLED devices. 20…”

“…It is known that TPBI can act as a better hole blocker than AlQ 3 . 20 The LUMO level of TPBI is lower than AlQ 3 , therefore can effectively stop the holes to move across the junction (Figure 4). It also has a wider HOMO-LUMO band gap, so that the blue emission can be readily re-absorbed by the emitting dye.…”