Near UV/Deep‐Blue Phenanthroimidazole‐Based Luminophores for Organic Light‐Emitting Diodes: Experimental and Theoretical Investigation

Abstract

AbstractTwo new deep blue phenanthroimidazole base luminophores 2‐(4‐(4‐(4‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenoxy)butoxy)phenyl)‐1‐phenyl‐1H‐phenanthro[9,10‐d]imid –azole (DPIPOBn) and 2‐(4‐(4‐(4‐(1‐(4‐tert‐butylphenyl)‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl) phenoxy)butoxy)phenyl)‐1‐(4‐tert‐butylphenyl)‐1H‐phenanthro[9,10‐d]imidazole (DPITBOBn) were designed and synthesized by linkage two phenanthroimidazole functional units via the highly flexible alkyl (butane) spacer with different N1 functional groups (benzene and tert‐butylbenzene). The synthesized luminophores were structurally characterized by spectroscopic method (1H, 13C, and mass). The photophysical, electrochemical and electroluminescence properties of the luminophores were systematically studied. These luminophores emit intense blue PL emission in both solution and solid phase. The HOMO‐LUMO energy level of the luminophores was calculated from Cyclic Voltammetry (CV) analysis and which agreed with the results from the density‐functional‐theory (DFT) calculation. The time‐dependent DFT (TD‐DFT) calculation was performed to know the excited states (singlet and triplet) of the luminophores. The solution‐processed OLED was fabricated to test these materials as emissive materials and as emitters. All the doped devices exhibited near‐UV emission with EL peaks centered around 380–395 nm with Commission International deL'Eclairage (CIE) coordinate of (0.16, 0.09 or 0.10). Among all the doped devices, DPITBOBn (3 wt%) based device displayed a power efficiency (PE) of 0.5 lm/W, a current efficiency (CE) of 1.2 cd/A and external quantum efficiency (EQE) of 1.9% at the brightness 100 cd/m2.