Significantly enhanced luminance and current efficiency for inorganic light-emitting devices have been obtained by tetrabutylammonium bromide (TBAB) additive into perovskite precursors. Reduced nonradiative defects primarily passivated by TBAB and increased exciton binding energy are responsible for improvement of PeLED performance. By employing a TBAB-treated interfacial layer, interface defects are reduced and it results in further promotion of electroluminescence performance of PeLED, including turn-on voltage of 2.6 V, brightness as high as 67 300 cd m-2, current efficiency of 22.5 cd A-1 and external quantum efficiency of 6.28%. Our results shed light on optimization of inorganic PeLEDs by focusing on the removal of defects both at the grain boundaries and the interfaces between carrier transport layers and perovskite emitting layers.