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

Abstract

CsPbX3 nanocrystal (NC)-based blue perovskite light-emitting diodes (PeLEDs) are still in a backward position while their green and red counterparts have achieved significant progress in the past few years. The emission spectrum of perovskite NCs can be manipulated via the ratio control of halides in precursor or halogen exchange of NCs. Herein, CsPbBrxCl3–x NCs are synthesized in ambient condition. With tetrabutylammonium p-toluenesulfonate (TBSA) added as the ligand during the purification process of as-synthesized perovskite NCs, bromine in NCs is substituted by chlorine and the spectrum undergoes a blue shift, whereas chlorine is exchanged by bromine in NCs and the spectrum undergoes a red shift by introducing sodium dodecylbenzenesulfonate (SDSA) as the ligand. The origin for halogen exchange can be attributed to the synergistic effects of the anion and cation of benzenesulfonates. The photoluminescence quantum yield (PLQY) of NCs increases from 7% to 81% due to the effective passivating effects of the strong ionic sulfonate heads, and the blue PeLEDs prepared by this method show a promising external quantum efficiency of 2.6%. Our work provides a new approach into spectral tuning of efficient blue PeLEDs.