Here the performance dependence of the organic light-emitting devices (OLEDs) on the location of a 0.5 nm LiF interlayer had been investigated,of which the thin LiF layer was used as a hole blocking and exciton confining layer. It was found that all the OLEDs exhibited improved efficiency when the LiF interlayer was used. When the LiF interlayer located 20-40 nm distance to the interface of TPD/Alq3,OLEDs showed peak electroluminescence efficiencies of around 4.5 cd/A,which is around 1.8 times of that in control device without LiF layer. Meanwhile,the current density of the devices increased when reducing the distance between LiF interlayer and cathode interface. The LiF interlayer was used to block the unrecombined holes at the interface between the recombination region and LiF interlayer,so that the electric field inside electron transport region increased,leading to a better electron transport and injection,improved charge balance and recombination probability in the recombination region. LiF interlayer may also confine the excitons in the recombination region and suppress the exciton quenching by the metal cathode.