Deep-Red Organic Light-Emitting Diodes with Increased External Quantum Efficiency and Extended Operational Lifetime by Managing the Composition of Mixed Cohosts

Abstract

To achieve high-performance and stable deep-red (DR)/near-infrared (NIR) organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters, here, a mixed cohost structure with carrier regulating capability was constructed by combining 2,6-bis(3-(9H-carbazol-9yl)phenyl)pyridine (26DCzPPy) with 1,3,5-tris(6-(3-(pyridin-3yl)phenyl)pyridin-2-yl)benzene (Tm3PyP26PyB) and optimizing the mixing ratios and thicknesses. The results indicated that this structure is efficient in modulating the carrier balance and boosting recombination probability due to effective blocking of excess holes and increased electron mobility. By employing the NIR TADF dye 7,10-bis(4-(diphenylamino)phenyl)-2,3-dicyanopyrazino-phenanthrene (TPA-DCPP) as a dopant, the optimized device obtained DR emission (663 nm) with an increased external quantum efficiency (EQE) of 16.4% and extended device lifetime LT 50 of 135 min, which are superior to those of reference and reported devices. Our investigations provide an effective and synergistic strategy for promoting the development of DR/NIR OLEDs.

High efficiency and high color purity deep‐blue organic light‐emitting diodes with blue index >500

“…The tunability of hole and electron features in the EML can be achieved by adjusting the ratio of p‐type host/n‐type host in the co‐host 18 . The optimal P/N host ratio contributes to realize efficient charge injection, transport, and recombination gearing towards the outstanding device performance 19,20 . Accordingly, three PSF devices with different p‐n host ratios of 6:4 (Device D), 5:5 (Device E), and 4:6 (Device F) were fabricated to fine tune the charge recombination zone and evaluate its effect on device performance following Device C1 stack (Figure 3A).…”

“…18 The optimal P/N host ratio contributes to realize efficient charge injection, transport, and recombination gearing towards the outstanding device performance. 19,20 Accordingly, three PSF devices with different p-n host ratios of 6:4 (Device D), 5:5 (Device E), and 4:6 (Device F) were fabricated to fine tune the charge recombination zone and evaluate its effect on device performance following Device C1 stack (Figure 3A). Table 2 and Figure 3B,C presented the performance data and curves of these three devices.…”