Electrochemical studies of silicon nitride electron blocking layer for all-solid-state inorganic electrochromic device

All-solid-state inorganic electrochromic devices (ECD) typically suffer from the leakage current which mainly arises from bulk defects and pinholes particularly in the ion conducting layer. The leakage current can lead to rapid self-bleaching of the ECD under open circuit, increased power consumption, and inhomogeneous coloration. Silicon nitride (Si3N4) thin films were prepared by pulsed DC reactive magnetron sputtering, and integrated into a monolithic inorganic ECD to reduce the leakage current. The device was prepared by a series of sputtering processes and the layer stacks were Glass/ITO/NiO/Si3N4/LiNbO3/Si3N4/WO3/ITO. The optimization of Si3N4 single layer was studied by electrochemical cyclic voltammetry. The effects of leakage current on electrical and optical properties of the ECDs were studied by chronoamperometry and cyclic voltammetry. The leakage current of the device is reduced from 216.0 to 32.1μA/cm2 with two 80nm-thick Si3N4 layers, and the open circuit memory effect is significantly improved. The optical modulation is 43% at 550nm by applied voltages of −2.0V and 1.5V.