Polaron States as a Massive Electron-Transfer Pathway at Heterojunction Interface.

For heterojunction semiconductor photoelectrodes, efficient charge separation is localized in the junction-induced electric field region and charge transfer follows a band-to-band charge-transfer pathway. Here, we found that polaron states at the heterojunction interface have a function of storing and transferring electrons. As a successful demonstration, we verified that the polaron states (Ti3+OH) on TiO2 are not passivated when used to create a CdS/TiO2 heterojunction and function as an efficient pathway for massively capturing, storing, and transferring the electrons from conduction bands of both TiO2 and CdS, thus effectively enhancing the charge separation efficiency of the heterojunction photoanode. The electron throughput of polaron states remains a positive correlation with polaron state density. Interfacial electron transfer through the TiO2 surface polaron states has great potential application in the development of high-performance heterojunction devices based on TiO2.