A wet- and dry-process feasible carbazole type host for highly efficient phosphorescent OLEDs

Abstract

A wet- and dry-process feasible host material is crucial to realize, respectively, low cost roll-to-roll fabrication of large area and high performance organic light-emitting diodes (OLEDs) with precise deposition of organic layers. We demonstrate in this study high efficiency phosphorescent OLED devices by employing a newly synthesized carbazole based host material 1,6-bis[3-(2-methoxy-3-pyridinyl)carbazol-9-yl]hexane (compound 5). Moreover, two other carbazole hosts 1,6-bis[3-(6-methoxy-3-pyridinyl)carbazol-9-yl]hexane (compound 4) and 3,6-di(2-methoxy-3-pyridinyl)-9-ethylcarbazole (compound 6) are also synthesized for comparison. By doping a typical green emitter fac tris(2-phenylpyridine)iridium (Ir(ppy)₃) in compound 5, for example, the resultant wet-processed device exhibits at 100 cd m⁻² a current efficiency of 27 cd A⁻¹ and a power efficiency of 16.1 lm W⁻¹. The dry-processed device shows a current efficiency of 61 cd A⁻¹ and a power efficiency of 62.8 lm W⁻¹. The high efficiency may be attributed to the host possessing an effective host-to-guest energy transfer, effective carrier injection balance, and the device architecture enabling excitons to generate on both the host and the guest.