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

Abstract

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 (η ext ) of 8.52%. Moreover, the η 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.

A large-scale deep-blue tetraphenylbenzene-bridged hybridized local and charge transfer fluorophore exhibiting small efficiency roll-off and low amplified spontaneous emission threshold

“…3c, PTPC shows a linear relationship between n a -n f and f with a slope of 6141 (Correlation = 0.967), corresponding to the dipole moment of S 1 of 15.77 D, demonstrating that there exists only one excited state in either low polar solvents or high polar ones. This character should be a quasi-equivalent hybridization HLCT state due to the strong interstate coupling of LE and CT (charge transfer) states, [31][32][33][34] which coincides well with theoretical calculations. This can be further proved using the transient PL decay curves in different solvents where only nanosecond-scale single-exponential decay lifetime (t) exists.…”

Color-tunable emission from violet-blue to pure-blue based on 5,9-disubstituted pyrene derivativesviaengineering of aryl-side groups

“…Although OLED has gradually realized commercialization in recent years, the restricted color gamut, 12 especially the shortage of excellent blue emitters [13][14][15] with high efficiency and long lifetime, still constrains the large-scale yields for the full-color large-area panels; so hunting for blue emitters with excellent performance is imperative. In general, p-conjugated polycyclic aromatic hydrocarbons (PAHs) with relatively wide energy gaps (B3.0-4.0 eV), for instance, pyrenes, [16][17][18][19] chrysenes, 20,21 anthracenes, 22,23 fluorenes, 24,25 fluoranthenes, 26,27 etc., can be expected to be desired blue OLED emitters by effective molecular design strategies.…”

Novel deep-blue hot exciton material for high-efficiency nondoped organic light-emitting diodes

“…Different from TADF and TTA materials, the RISC of the hot exciton materials is carried out from a high-lying triplet state (T n , n ≥ 2) to a singlet state (S m , m ≥ 1), and theoretically, 100% exciton utilization can be achieved, and the efficiency of the device can also be greatly improved. 14–16 In this case, the small energy spitting design of S 1 and T 1 states is not necessarily for hot exciton materials; thus, the S 1 state can be a local excited (LE) state or a hybridized local and charge-transfer (HLCT) state, which is more suitable for constructing blue and deep-blue materials. Benefitting from this innate advantage, some high-efficiency deep-blue and near-ultraviolet hot exciton materials have been successfully obtained.…”