Effect of a critical percolation threshold in purified short carbon nanotube-polymer/ZnS:Cu,Cl composite on electroluminescence

► The EL devices were fabricated using the SWCNT-polymer/ZnS:Cu,Cl composite. ► SWCNTs were shortened by cryo-crushing and purified by thermal treatment. ► The composite EL device exhibited a 100% increase in luminance at 0.09 wt.% of SWCNTs. ► SWCNTs could increase charge carrier tunneling into ZnS lattice by field enhancement. ► This can increase the electron-hole recombination to produce more light emission.