Strongly enhanced and tunable photovoltaic effect in ferroelectric-paraelectric superlattices

• Published in: Science advances Vol. 7; no. 23
• Main Authors: Yun, Yeseul, Mühlenbein, Lutz, Knoche, David S., Lotnyk, Andriy, Bhatnagar, Akash
• Format: Journal Article
• Language: English
• Published: American Association for the Advancement of Science 01.06.2021
• Subjects: Applied Physics; Materials Science; SciAdv r-articles
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.abe4206

Sandwiching a ferroelectric between two paraelectrics squeezes out larger photovoltaic current. Ever since the first observation of a photovoltaic effect in ferroelectric BaTiO 3 , studies have been devoted to analyze this effect, but only a few attempted to engineer an enhancement. In conjunction, the steep progress in thin-film fabrication has opened up a plethora of previously unexplored avenues to tune and enhance material properties via growth in the form of superlattices. In this work, we present a strategy wherein sandwiching a ferroelectric BaTiO 3 in between paraelectric SrTiO 3 and CaTiO 3 in a superlattice form results in a strong and tunable enhancement in photocurrent. Comparison with BaTiO 3 of similar thickness shows the photocurrent in the superlattice is 10 3 times higher, despite a nearly two-thirds reduction in the volume of BaTiO 3 . The enhancement can be tuned by the periodicity of the superlattice, and persists under 1.5 AM irradiation. Systematic investigations highlight the critical role of large dielectric permittivity and lowered bandgap.