Highly Efficient Green Light-Emitting Diodes from All-Inorganic Perovskite Nanocrystals Enabled by a New Electron Transport Layer

Adopting proper electron transport layers (ETLs) is essential to high-performance all-inorganic perovskite light-emitting diodes (PeLEDs). However, the effect of ETLs has not been comprehensively investigated in all-inorganic nanocrystal PeLEDs, while 2,2',2 ''-(1,3,5-benzenetriyl) tris-[1-phenyl-1H-benzimidazole] (TPBi) is the most common ETL. Herein, a novel strategy is proposed to enhance the efficiency of nanocrystal PeLEDs. Tris(8-hydroxyquinoline) aluminum (Alq(3)) is incorporated into TPBi to form a new ETL TPBi/Alq(3)/TPBi, simultaneously enabling charge balance and confinement. The green PeLED with new ETL exhibits a maximum external quantum efficiency (EQE) of 1.43%, current efficiency of 4.69 cd A(-1), and power efficiency of 1.84 lm W-1, which are 191%, 192%, and 211% higher than those of PeLEDs with conventional ETL TPBi, respectively. Significantly, the EQE is 36-fold higher than that of PeLED with high electron mobility ETL. Impressively, the full width at half-maximum of electroluminescence emission is 16 nm, which is the narrowest among CsPbBr3 PeLEDs. The findings may present a rational strategy to enhance the device engineering of all-inorganic PeLEDs.