Highly Efficient and Stable CsPbBr3 Perovskite Photoanodes Based on Inverse Opal TiO2 Layers in Photoelectrochemical Water Splitting.

Abstract

CsPbBr3, an inorganic halide perovskite compound, has attracted significant attention in the photoelectrochemical water splitting (PEC-WS) process due to its excellent properties; i.e. low cost, processing at ambient temperature and humidity, tunability of the bandgap, long carrier transport length, and reasonable stability. Despite these advantages, CsPbBr3 possesses a weak optical absorption in the visible, limiting its performance for photoelectrochemical applications. To address this issue, we propose and validate the use of inverse opal of TiO2 (IOT) as a scaffold for CsPbBr3 in water splitting devices with TiO2 as the electron transprt layer. We observed that using IOT improves PEC-WS performance mainly due to two effects: i) improved light absorption in the visible region and ii) enhanced charge transfer within the elctrode. A carbon ink composed of carbon black, graphite, and carbon waste toner is applied onto the perovskite layer to improve its stability in the electrolyte and to enhance charge injection from the electrode into the electrolyte. A high photocurrent density of 7.28 mA.cm-2 at 1.23 V vs reversible hydrogen electrode (RHE) was obtained and maintained for 10000s at pH=7 for the photoanode with the configuration of Glass/FTO/‌Compact-TiO2/Mesoporous-TiO2/Inverse Opal TiO2/CsPbBr3/C without using any co-catalyst. Our findings confirm that inverse opal optical nanostructures as electron transport layer have the potential to address the basic material issues of water-splitting devices based on CsPbBr3.