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In this study, the effects of thin Li-halide cathodic interlayers on electron injection were examined for electroluminescent layers of polymer light-emitting diodes (PLEDs). An order of magnitude increase in current density is observed as Li-halide salts are varied down the group VII column of the periodic table. When considering luminance, devices with a LiCl interlayer were 2.3× greater than those with LiF, whereas devices with LiBr were 2.8× greater, while concurrently lowering the turn-on voltage. This resulting enhanced current density and subsequent luminance could be due to a lowered work-function difference at the cathode created by either the Li-halides dissociation-induced doping of the polymer surface or an interfacial dipole of ionic Li-halide compound, leading to band bending.