Single White‐Emitting Polymers with High Efficiency, Low Roll‐Off, and Enhanced Device Stability by Using Through‐Space Charge Transfer Polymer with Blue Delayed Fluorescence as Host for Yellow Phosphor

Abstract

White‐emitting polymers hold great promise for the production of low‐cost and large‐area light sources via solution process. However, the development of efficient and stable white‐emitting polymers has been a formidable challenge yet. Here a strategy for single white‐emitting polymers is demonstrated with high efficiency, low roll‐off, and enhanced device stability by using through‐space charge transfer (TSCT) polymer with small singlet‐triplet energy splitting and blue thermally activated delayed fluorescence as host for yellow phosphor. This strategy not only combines delayed fluorescence and phosphorescence in one polymer to make full use of excitons but also enables the long‐range Förster resonant energy transfer from polymer host to phosphor for suppressing triplet quenching at high luminance, leading to state‐of‐the‐art luminous efficiency of 50.9 cd A−1 at 1000 cd m−2 (corresponding to a low roll‐off of 1.9%) for white‐emitting polymers, together with a tenfold increase in device lifetime over the control polymers based on a conventional polymer host. These results shed light on the prospect of using TSCT polymer with delayed fluorescence as host for developing efficient and stable white‐emitting polymers for solution‐processed white organic light‐emitting diodes.

Through‐space charge transfer polymers for solution‐processed organic light‐emitting diodes

“…Moreover, TSCT polymers can also be utilized as host materials for white electroluminescence. [66] First, TSCT polymers are composed of electron-rich donor and electrondeficient acceptor, making them capable to transport both holes and electrons in emissive layer. Second, the small ΔE ST for TSCT polymers can maintain high triplet energy level (T 1 ) and low singlet energy level (S 1 ), which is favorable for confining triplet excitons on emissive species and meanwhile keeping smooth carrier injection ability from adjacent layers.…”

“…[11,12] Third, the electron clouds of donor and acceptor can communicate with each other through spatial interactions to enhance the radiative decay rate, giving promising PLQY for the designed polymers. Based on this strategy, three kinds of TSCT polymers with different topological structures, including linear, [61][62][63][64][65][66] bottlebrush, [67] and dendritic architectures [68,69] , have been developed so far (Figure 1). In this review, current advances in TSCT polymers for solution-processed OLEDs are summarized.…”

Tris(triazolo)triazine-based emitters for solution-processed blue thermally activated delayed fluorescence organic light-emitting diodes

“…TADF polymers have shown promise as emitters in solution-processed devices. 23,[26][27][28] However, the synthesis of polymers will lead to a mixture of compounds with different molecular weight, each of which will have a slightly different set of photophysical properties that will result in a broadened emission spectrum. 29 Moreover, the photophysical properties of TADF polymers usually suffer due to quenching via intra-and inter-molecular charge transfer between the TADF units on the polymer.…”

Core–Shell Fluorescent Polymeric Particles with Tunable White Light Emission Based on Aggregation Microenvironment Manipulation

“…White-light emitting polymers (WLEPs) have attracted increasing attentions because of their promising applications in backlighting for liquid-crystal displays, full-color flat-panel displays, solid-state lighting, and so on, exhibiting the unique advantages of flexibility, low cost and large-area manufacturing. [1] Up to now, the most exploited strategy to develop WLEPs is reasonable combination of multiple components with three primary or two complementary emission colors into polymers, [2] in which the notorious aggregation-caused quenching (ACQ) effect, [1a, 3] intrinsic phase separation, [4] and excess Fçrster resonance energy transfer (FRET) [5] seriously trouble the researchers in practice. To address these issues, much effort has been devoted to pursuing reasonable approaches to develop superior WLEPs.…”