LAUSR

Abstract Efficient control on the growth of organic crystalline films is crucial for developing organic electroluminescent devices. Herein, a highly crystalline thin film of a blue-light-emitting material, 1,2-diphenyl-1H-phenanthro[9,10-d]imidazole (PPI) derivative, 1,4-bis(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)benzene (ρ-DPPI), has been achieved by the weak epitaxy growth (WEG) method. The ρ-DPPI molecules with an edge-on orientation grow epitaxially on the inducing layer, forming the continuous and uniform crystalline thin film. The photoluminescence (PL) spectrum of the ρ-DPPI thin film fabricated by weak epitaxy growth was blue-shifted relative to that of the amorphous ρ-DPPI thin film. Also, its PL quantum yield was measured and found to be 64.5%. The electroluminescence performance was evaluated and a fluorescent OLED that emits deep-blue light with Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.11) has been achieved. The device exhibits high performance with a maximum current efficiency, power efficiency and external quantum efficiency of 4.5 cd A−1, 4.1 lm W−1 and 4.1% at 200 cd m−2, which demonstrates its potential as a highly efficient emitter. The further adoption of the WEG method would advance the knowledge of the growth behavior of luminescent materials and provide desired properties for their electroluminescent applications.