We　report　here　the　all-solution-processed,　high-efficiency　quantum　dot　light　emitting　diode　(QLED)　employing　inorganic　copper　(I)　thiocyanate　(CuSCN)　as　hole　injection　layer.　In　comparison　with　the　widely　used　injection　material　of　poly(3,4-ethylenedioxythiophene):　poly(styrene　sulfonate)　(PEDOT:PSS),　the　hole　injection　into　the　QD　layer　is　significantly　improved,　allowing　low　turn-on　voltage,　high　luminance　and　efficiency.　By　optimizing　the　multilayer　structure　and　synergistically　balancing　the　carrier　injection,　the　resulting　OLEDs　exhibit　high　performance　with　the　maximum　current　efficiency　of　52.4　cd/A　and　external　quantum　efficiency　of　12.0%　for　green　device,　17.0　cd/A　and　16.2%　for　red　device.　These　results　indicate　that　CuSCN　is　a　reliable　hole　transport　materials　for　low-cost,　high-efficiency　QLED　devices.