Structural Optimization of BODIPY Derivatives: Achieving Stable and Long-Lived Green Emission in Hyperfluorescent OLEDs
Yogesh Gawale, Paramasivam Palanisamy, Hyun Seung Lee, Ajeet Chandra, Hae Ung Kim, Rasheeda Ansari, Mi Young Chae, Jang Hyuk Kwon
Abstract
Boron dipyrromethene (BODIPY) derivatives are widely studied as terminal emitters in organic light-emitting diodes (OLED) due to their narrow emission and high photoluminescence quantum yield (PLQY). However, the strategy for precisely tuning their emission toward a high color purity is still challenging. Herein, we developed a new design strategy to regulate the emission of BODIPY derivatives by modifying the electronic and steric dominance using functionalities, such as nitrile, pentafluorophenyl, diethyl, and monobenzyl. These rational modifications yielded a series of four novel green BODIPY emitters, namely, tPN-BODIPY, tPPP-BODIPY, tPBn-BODIPY, and tPEN-BODIPY, each benefited with a tuned emissions range of 517 to 542 nm with a narrow fwhm of 25 nm and high photoluminescence quantum yield up to 96%. Among these synthesized BODIPYs, an unsymmetrical tPBn-BODIPY was chosen as a final dopant (FD) to explore its application in OLED devices. The fabricated TADF sensitized fluorescence-OLED (TSF-OLED) exhibits a narrow band pure green emission at 531 nm with corresponding CIE coordinates of ( x, y ) = (0.27, 0.68) and a maximum external quantum efficiency (EQE) of 20%. Furthermore, the TSF-OLED displayed an exceptionally prolonged device operational lifetime (LT 90 ) of 210 h at an initial luminescence of 3000 cd m –2 .