Bifunctional Bicarbazole-Benzophenone-Based Twisted Donor–Acceptor–Donor Derivatives for Deep-Blue and Green OLEDs

Abstract

Organic light-emitting diodes (OLEDs) have played a vital role in showing tremendous technological advancements for a better lifestyle, due to their display and lighting technologies in smartphones, tablets, television, and automotive industries. Undoubtedly, OLED is a mainstream technology and, inspired by its advancements, we have designed and synthesized the bicarbazole-benzophenone-based twisted donor–acceptor–donor (D-A-D) derivatives, namely DB13, DB24, DB34, and DB43, as bi-functional materials. These materials possess high decomposition temperatures (>360 °C) and glass transition temperatures (~125 °C), a high photoluminescence quantum yield (>60%), wide bandgap (>3.2 eV), and short decay time. Owing to their properties, the materials were utilized as blue emitters as well as host materials for deep-blue and green OLEDs, respectively. In terms of the blue OLEDs, the emitter DB13-based device outperformed others by showing a maximum EQE of 4.0%, which is close to the theoretical limit of fluorescent materials for a deep-blue emission (CIEy = 0.09). The same material also displayed a maximum power efficacy of 45 lm/W as a host material doped with a phosphorescent emitter Ir(ppy)3. Furthermore, the materials were also utilized as hosts with a TADF green emitter (4CzIPN) and the device based on DB34 displayed a maximum EQE of 11%, which may be attributed to the high quantum yield (69%) of the host DB34. Therefore, the bi-functional materials that are easily synthesized, economical, and possess excellent characteristics are expected to be useful in various cost-effective and high-performance OLED applications, especially in displays.

Naphtalimide-Based Bipolar Derivatives Enabling High-Efficiency OLEDs

“…This successful outcome indicates the creation of an efficient and stable green OLED device, with a maximum EL peak at 520 nm. An optimal balance between efficient energy transfer and charge transport results in improved device performance [ 21 ].…”

Bicarbazole-Benzophenone-Based Twisted Donor-Acceptor-Donor Derivatives as Blue Emitters for Highly Efficient Fluorescent Organic Light-Emitting Diodes

“…9-(2-Ethylhexyl)-9′H-3,3′-bicarbazole ( 4 ) was prepared by a similar method which was published earlier [ 27 ].…”

“…): 8.29 (s, 2H), 8.11-8.06 (m, 2H), 7.73-7.67 (m, 2H), 7.41-7.32 (m, 6H), 7.17 (t, 2H, J = 7.2 Hz), 4.29 (t, 2H, J = 7.2 Hz), 1.79 (quint, 2H, J = 7.2 Hz), 1.38-1.29 (m, 2H), 0.87 (t, 3H, J = 7.2 Hz). 13 9-(2-Ethylhexyl)-9 ′ H-3,3 ′ -bicarbazole (4) was prepared by a similar method which was published earlier [27]. 9-Octyl-9 ′ H-3,3 ′ -bicarbazole ( 5): 1-Bromooctane (1.16 g, 6.0 mmol) was added to a stirred solution of 3,3 ′ -bicarbazole (2) (2.00 g, 6.0 mmol) in 50 mL of tetrahydrofuran.…”

“…Recently, we published carbazole-diphenyl sulfone-carbazole (D-A-D) bipolar blue light emitting materials for first-generation OLEDs. One device outperformed others by showing a peak external quantum efficiency (EQE max ) of 4.0% for deep-blue emission (CIE y = 0.09) [ 27 ].…”

Highly fluorescent room temperature liquid crystalline S-annulated swallow tail perylene bisimide exhibiting enhanced electroluminescence (EQE > 11%)

“…However, higher dopant concentrations can also expedite non-radiative decay pathways, including quenching processes and triplet–triplet annihilation, thereby contributing to the observed decrease in device efficiency. 38–41 Furthermore, Table 5 clearly illustrates the underperformance of the host-free undoped device, primarily attributed to an insufficient charge balance within the emissive layer. While the doped device has demonstrated notable improvements, this underscores the pivotal role played by the host material in achieving optimal device performance.…”