Metal halide perovskites, known for their outstanding optical properties such as high photoluminescence quantum yield, exceptional color purity, and tunable bandgap, have emerged as promising semiconductor materials for next -generation display technologies. Nonetheless, producing pure red emissions from - 10 nm-sized CsPbI 3 perovskite nanocrystals (PeNCs) remains a signi ficant challenge for perovskite light -emitting didoes (PeLEDs). Here, we present the facile surface bromination strategy of CsPbI 3 PeNCs for pure red PeLEDs. The mild post-ligand treatment on CsPbI 3 PeNCs produces surface-brominated PeNCs, denoted as CsPbI 3 :Br, while preserving the original CsPbI 3 crystal structure intact. The resulting CsPbI 3 :Br PeNCs exhibit bright pure red luminescence and signi ficant improvements in electrical properties. The PeLEDs, fabricated with these PeNCs, achieve a remarkable external quantum ef ficiency (EQE) of 19.8 %, comparable to those of the best reported pure red PeLEDs. Finally, we have showcased the application of these PeLEDs as skin -attachable PeLEDs, showing stable operations under various mechanical deformations. This study not only provides a straightforward method for producing pure red PeNCs, but also highlights their potential in wearable electronic applications.