Monochromatic and electrochemically switchable electrochemiluminescence of perovskite CsPbBr₃ nanocrystals

Cubic-shaped perovskite CsPbBr₃ nanocrystals (NCs) could be electrochemically injected with holes (or electrons) to produce several charged states under different oxidizing and reducing potentials, and then bring out electrochemiluminescence (ECL) of higher color purity than traditional ECL chemicals and metal chalcogenide NCs, in both annihilation and co-reactant routes. The difference of electrochemical gaps between varied hole and electron injecting potentials displayed little effect on the ECL spectrum and colour purity of CsPbBr₃ NCs. All the excited states generated under different oxidizing and reducing potential couples in ECL of CsPbBr₃ NCs were the same as those in photoluminescence, as all the ECL spectra were almost identical to the CsPbBr₃ NCs' photoluminescence spectrum. Importantly, the ECL of CsPbBr₃ NCs was electrochemically switchable and displayed an obvious "on/off" type feature by changing the sequence of hole injecting and electron injecting processes, as strong ECL could be obtained by injecting holes onto the electron injected NCs, while no or very weak ECL was obtained in the reversed way.