Bis-Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue-Emitting OLEDs.

Hsin-Hung Kuo,Yi-Kuang Chen,Yun Chi,Ze-Lin Zhu,Shih-Hung Liu,Pi-Tai Chou,Chun-Sing Lee,Alex K-Y Jen

doi:10.1002/advs.201800846

Abstract

Sky‐blue and blue‐emitting, carbazolyl functionalized, bis‐tridentate Ir(III) phosphors Cz‐1–Cz‐3 with bright emission and short radiative lifetime are successfully synthesized in a one‐pot manner. They exhibit very high photostability against UV–vis irradiation in degassed toluene, versus both green and true‐blue‐emitting reference compounds, i.e., fac‐[Ir(ppy)3] and mer‐[Ir(pmp)3]. Organic light‐emitting diodes (OLEDs) based on Cz‐2 exhibit maximum external quantum efficiency (EQE) of 21.6%, EQE of 15.1% at 100 cd m−2, and with CIEx , y coordinates of (0.17, 0.25). This study provides a conceptual solution to the exceedingly stable and efficient blue phosphor. It is promising that long lifespan blue OLED based on these emitters can be attained with further engineering of devices suitable for commercial application.

Highlights

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It is promising that long lifespan blue Organic light-emitting diodes (OLEDs) based on these emitters can be attained with further engineering of devices suitable for commercial application

Summary

Normalized Intensity

These characteristics are clearly superior to those displayed by other relevant bis-tridentate Ir(III) emitters[18,29] and fall in the ranking column of typical tris-bidentate blue-emitting Ir(III) phosphors.[30] The recorded CIE coordinates are still deviated from the NTSC blue standard (0.14, 0.08), e.g. National Television System Committee USA This shortcoming can be fixed by employment of microcavity effect and/or using color filter in commercial OLEDs. serious efficiency roll-off was obtained as increasing luminance (Figure 4 and Table 3), especially at above 1000 cd m−2, which seems contradicting the better photophysical robustness of emitters.

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Findings

Conflict of Interest