Excellent n-type light emitters based on AIE-active silole derivatives for efficient simplified organic light-emitting diodes

Abstract

In order to fabricate high-performance, non-doped and simplified OLEDs, excellent p/n-type light emitters with both high solid-state emission efficiencies and good carrier-transporting abilities are urgently needed, especially efficient n-type light emitters. Herein, we designed and synthesized four new silole derivatives, (PBI)₂DMTPS, (PBI)₂MPPS, (PPI)₂DMTPS, and (PPI)₂MPPS, consisting of the 2,3,4,5-tetraphenylsilole unit and 1-phenyl-1H-benzo[d]imidazole (PBI) or 1-phenyl-1H-phenanthro[9,10-d]imidazole (PPI) groups. These novel siloles are aggregation-induce emission (AIE)-active and highly emissive in solid films, and show good thermal stabilities and low LUMO energy levels. It is noteworthy that the amorphous films of (PBI)₂DMTPS and (PBI)₂MPPS present high electron mobilities of 1.24 × 10⁻⁴ and 3.42 × 10⁻⁴ cm² V⁻¹ s⁻¹, respectively, at an electric field of 5.5 × 10⁵ V cm⁻¹, which are superior to that of 1,3,5-tris(phenyl-2-benzimidazolyl)benzene (TPBi). The non-doped trilayer OLED of (PPI)₂DMTPS exhibits an outstanding electroluminescence (EL) performance with efficiencies of 15.06 cd A⁻¹, 16.24 lm W⁻¹ and 4.84%. More importantly, an efficient double-layer OLED is achieved based on (PBI)₂DMTPS, offering comparable EL efficiencies (13.30 cd A⁻¹, 14.51 lm W⁻¹ and 4.25%) with respect to those of its trilayer OLED (13.50 cd A⁻¹, 12.58 lm W⁻¹ and 4.22%). These results demonstrate an effective approach towards n-type light emitters for efficient, simplified and low-cost OLEDs.