Growth of Doped SrTiO₃ Ferroelectric Nanoporous Thin Films and Tuning of Photoelectrochemical Properties with Switchable Ferroelectric Polarization

Ferroelectric polarization is an intriguing physical phenomenon for tuning charge-transport properties and finds application in a wide range of optoelectronic devices. So far, ferroelectric materials in a planar geometry or chemically grown nanostructures have been used. However, these structural architectures possess serious disadvantages such as small surface areas and structural defects, respectively, leading to reduced performance. Herein, the growth of room-temperature ferroelectric nanoporous/nanocolumnar structure of Ag,Nb-codoped SrTiO₃ (Ag/Nb:STO) using pulsed laser deposition is reported and demonstrated to have enhanced photoelectrochemical (PEC) properties using ferroelectric polarization. By manipulating the external electrical bias, ∼3-fold enhancement in the photocurrent from 40 to 130 μA·cm^-2 of film area is obtained. Concurrently, the flat-band potential is decreased from -0.55 to -1.13 V, revealing a giant ferroelectric tuning of the band alignment at the semiconductor surface and enhanced charge transfer. In addition, an electrochemical impedance spectroscopy study confirmed the tuning of the charge transfer with ferroelectric polarization. Our nanoporous ferroelectric-semiconductor approach offers a new platform with great potential for achieving highly efficient PEC devices for renewable energy applications.