A Breakthrough in Color‐Tunable All‐Fluorescent White OLEDs through the Cooperation Between a New Blue HLCT Fluorophore and a Long‐Wavelength TADF Emitter

Abstract

It is a vitally important and challenging task to achieve high efficiency and wide color‐tunable white organic light emitting diodes (CT‐WOLEDs) meeting the needs of various decoration and lighting applications. Here, a high‐performance single‐cell all‐fluorescent CT‐WOLED with a single‐doped single‐emissive‐layer structure has been developed employing a multi‐functional hybrid local and charge transfer (HLCT) fluorophore 2‐(4‐(9H‐carbazol‐9‐yl)−2′,5′‐difluoro‐[1,1′:4′,1′'‐terphenyl]−4‐yl)−1‐phenyl‐1H‐phenanthro[9,10‐d]imidazole (PICZ2F) as a deep‐blue emitter as well as an effective host for a yellow thermally activated delayed fluorescence emitter. The record‐breaking power efficiency of 89.50 lm W‒1 and correlated color temperature (CCT) span from 3749 to 18 279 K are achieved simultaneously, which is not only one of the state‐of‐the‐art CT‐WOLEDs reported so far, but also comparable to the best values from all‐fluorescent white devices with a single‐emissive‐layer. Moreover, by using PICZ2F as an emitter, an external quantum efficiency (EQE) of 7.10% with the Commission Internationale de lEclairage (CIE) coordinates of (0.155, 0.068) is achieved in the doped device, and a low‐efficiency roll‐off even at a high luminance of 15 000 cd m−2 (EQE15000: 5.80%) is achieved in the non‐doped device. Overall, the findings provide a promising strategy to develop simple but efficient CT‐WOLEDs.

A record-high EQE of 7.65%@3300 cd m−2 achieved in non-doped near-ultraviolet OLEDs based on novel D′–D–A type bipolar fluorophores upon molecular configuration engineering

“…Organic light-emitting diodes (OLEDs) have achieved large-scale commercial applications in full-color displays and solid-state lighting due to their unique advantages. 1–6 However, compared to red, green, and blue (RGB) OLEDs, 5,7–10 the development of near-ultraviolet (NUV) OLEDs with a Commission Internationale de l’Eclairage y coordinate (CIE y ) below 0.035 is dropping noticeably behind. It's known that NUV emitters have broad application space and development prospects in the fields of optoelectronics, excitation light sources, high-density information storage, biological and medical applications.…”

Conformational Isomerization Promotes Balanced Ambipolar Transport for Efficient Narrowband Near-Ultraviolet Fluorophore and Non-doped Device with Low Efficiency Roll-Off

“…Organic light-emitting diodes (OLEDs) with near-ultraviolet (NUV) emission have drawn tremendous attention in the promising applications of high-density information storage, medical light therapy, excitation lighting source, and chemical and biological sensors. Nevertheless, compared to the rapidly developing trichromatic (red, green, and blue) organic electroluminescence (EL) materials and OLEDs, − the variety and performance of NUV materials and devices lag behind because of their intrinsic wider bandgaps, − especially in the case of non-doped OLEDs. In the EL process, electrons and holes are injected into the electron and hole injection layers from the cathode and anode, respectively.…”