Spectral Tuning of Efficient CsPbBr_<i>x</i>Cl_3–<i>x</i> Blue Light-Emitting\nDiodes <i>via</i> Halogen Exchange Triggered by Benzenesulfonates

Abstract

CsPbX₃ nanocrystal (NC)-based blue perovskite light-emitting\ndiodes (PeLEDs) are still in a backward position while their green\nand red counterparts have achieved significant progress in the past\nfew years. The emission spectrum of perovskite NCs can be manipulated <i>via</i> the ratio control of halides in precursor or halogen\nexchange of NCs. Herein, CsPbBr_<i>x</i>Cl_3–<i>x</i> NCs are synthesized in ambient\ncondition. With tetrabutylammonium <i>p</i>-toluenesulfonate\n(TBSA) added as the ligand during the purification process of as-synthesized\nperovskite NCs, bromine in NCs is substituted by chlorine and the\nspectrum undergoes a blue shift, whereas chlorine is exchanged by\nbromine in NCs and the spectrum undergoes a red shift by introducing\nsodium dodecylbenzenesulfonate (SDSA) as the ligand. The origin for\nhalogen exchange can be attributed to the synergistic effects of the\nanion and cation of benzenesulfonates. The photoluminescence quantum\nyield (PLQY) of NCs increases from 7% to 81% due to the effective\npassivating effects of the strong ionic sulfonate heads, and the blue\nPeLEDs prepared by this method show a promising external quantum efficiency\nof 2.6%. Our work provides a new approach into spectral tuning of\nefficient blue PeLEDs.