Highly Efficient Blue Organic Light-Emitting Diode Based on a Pyrene[4,5-d]Imidazole-Pyrene Molecule

Organic light-emitting diodes (OLEDs), which have been recently utilized in some flat-panel display screens such as mobile phones and televisions, show many merits, including light weight, high flexibility, energy preservation, and so forth, and are considered the next-generation displays and solid-state lightings. Blue-emitting materials that can be applied in nondoped OLEDs with little efficiency roll-offs at high brightness are of great importance. Here, a highly efficient, blue-emitting material, 9-phenyl-10-(4-(pyren-1-yl)phenyl)-9H-pyreno[4,5-d]imidazole (PyPI-Py), is achieved using pyrene[4,5-d]imidazole and pyrene as the weak electron donor and electron acceptor, respectively. The nondoped blue OLED exhibits excellent performance with a maximum brightness of 75,687 cd m(-2), a maximum current efficiency of 13.38 cd A(-1), and a maximum external quantum efficiency (eta(ext)) of 8.52%. Moreover, the eta(ext) is maintained at 8.35% and 8.05% at a brightness of 10,000 and 50,000 cd m(-2), respectively, displaying extremely small efficiency roll-offs of 2.0% and 5.5%. The device characteristics are among the highest values for nondoped blue OLEDs and correspond to the best performance obtained for nondoped pyrene-based blue OLEDs. The superior performance is attributed to the proper donor-acceptor design strategy which results in a quasi-equivalent hybrid local and charge-transfer excited state with the maximum generation of an 82% fraction of singlet excitons.

Automated summary

Organic light-emitting diodes (OLEDs) are widely used in flat-panel display screens such as mobile phones and televisions due to their light weight, high flexibility, and energy efficiency. In this study, a highly efficient blue-emitting material for nondoped OLEDs was achieved using a proper donor-acceptor design strategy. The resulting OLED exhibited excellent performance with high brightness, current efficiency, and external quantum efficiency, as well as minimal efficiency roll-off.