Enhanced Carrier Dynamics of CsPbBr₃ Nanocrystals Enabled by Short-Ligand Ethanedithiol for Efficient...

Photoelectrochemical (PEC) water splitting is a potential solution for a low-carbon society and clean energy storage due to its ability to produce hydrogen and oxygen. However, the slow oxidation half-reaction of the process has limited its overall efficacy, necessitating the development of an efficient photoanode. Colloidal CsPbBr₃ nanocrystals (NCs) have been identified as promising candidates due to their high light absorption and valence band position. However, the presence of the electrical insulator, long-chain oleate molecules, on the surface of the CsPbBr₃ NCs has hindered efficient charge carrier separation and transport. To solve this problem, short-chain 1,2-ethanedithiol (EDT) ligands were used to replace the oleate ligands on the surface of the CsPbBr₃ NCs through a solid-state ligand exchange method. This resulted in a reduction of the nanocrystal spacing and a cross-linking reaction, which improved the photogenerated carrier separation and transport while still passivating the dangling bonds on the CsPbBr₃ NC surface. Ultimately, this led to a remarkable photocurrent density of 3.34 mA cm^-2 (1.23 V_RHE), which was 5.2 times higher than that of the pristine oleate-CsPbBr₃ NC (0.64 mA cm^-2)-based device. This work presents an efficient way of developing inorganic lead halide perovskite colloidal nanocrystal-based photoanodes through surface ligand engineering.