Achieving Solution‐Processed Non‐Doped Single‐Emitting‐Layer White Organic Light‐Emitting Diodes through Adjusting Pyrene‐Based Polyaromatic Hydrocarbon

Abstract

Single‐emitting‐layer white organic light‐emitting diodes (SEL‐WOLEDs) have developed rapidly in recent years due to the outstanding advantages of high efficiency, simple device structure, low cost, less phase separation, and stable emission color. Nevertheless, the relatively complicated host‐dopant system is usually essential for most previous SEL‐WOLEDs and the development of simple non‐doped SEL‐WOLEDs lags behind. Hence the straightforward synthesis of single‐white‐emitting molecules for non‐doped SEL‐WOLEDs still remains a great challengeable task. In this article, we designed and synthesized two new pyrene‐based polyaromatic hydrocarbons (PAHs) and used them as emitting layer materials in the OLED devices. When the molecules change from the mono‐fused one to bis‐fused one, the emitting light changes from greenish to white color. Further study indicated that the bis‐fused molecule PyD with more twisted and extended backbone packed in neat Cmca space group in single‐crystal system compared with P21/n for PyS, which may be favorable to form excimers in the solid state and broaden the emission spectrum in the OLEDs. As a result, a solution‐processed non‐doped single‐white‐emitting‐molecule SEL‐WOLED with high performance (e. g., a high color rendering index of 66) is reported. The findings will be beneficial not only to further development of simple WOLEDs, but also to other related organic optoelectronic technology.

Advances in Host-Free White Organic Light-Emitting Diodes Utilizing Thermally Activated Delayed Fluorescence: A Comprehensive Review

“…We listed four common types of TADF-WOLEDs, as shown in Figure 1 , and summarized the key data from their representative literature in Table 1 . Most research works concerning OLEDs are carried out based on doping and excitable compounds, but at the same time, there are problems such as complex device structure [ 34 , 35 ], strict doping ratio [ 36 , 37 ], and easy contamination during the evaporation process [ 38 ]. However, ultrathin WOLEDs (the luminous layer is usually a few nanometers or even less than 1nm of the device) can make it easier to conduct experiments by virtue of its simple device structure.…”

Organic Light-Emitting Diodes with Ultrathin Emitting Nanolayers

“…In UEN-based OLEDs, as the name implies, the emitting layer is usually very thin (e.g., <1 nm) compared to the doped OLEDs. The exploitation of UENs does not have to use doping technology since it can form a similar co-doping effect with adjacent layers, which makes the device structure and fabrication process more simplified [25][26][27]. In addition, the device design becomes more flexible, and the material consumption and manufacturing costs are lowered [28,29].…”