Dr. Yang Bai, Associate Professor at the University of Oulu, has been selected to receive the 2026 D. T. Rankin Award from the Energy Materials and Systems Division (EMSD) of the American Ceramic Society. The award recognizes outstanding service to EMSD, where Dr. Bai served a four-year term on positions of Programme Chair, Secretary, Vice-Chair and Chair. Dr. Bai has contributed to managing and growing the division as well as to promoting research of energy technologies among materials scientists.

At the Materials Science & Technology 2026 conference (MS&T26) held on October in Pittsburgh, USA, Dr. Bai received the award and delivered an award lecture with title Advances and bottlenecks in energy harvesting technologies – How far are we from sustainable IoT? Energy harvesting is the research area Dr. Bai and his research team specializes in.

The recognition coincides with the publication of Bai's latest research article in Applied Physics Letters, where his team reports a new approach for probing the electronic structure of ferroelectric oxides through temperature-dependent photoconductivity measurements.

Electrons in most semiconductor materials are thought to be irresponsive under light that carries photons with energy smaller than their bandgap. Using the temperature-dependent photoconductivity measurement, some previously inaccessible electronic states can be activated even under such below-bandgap light. By measuring the change in electrical conductivity under varying photon energy and temperature, researchers can now discover how these highly immobile electrons move and settle, thus unlocking an additional degree of freedom to design, engineer and utilize insulating materials in electronic components. For example, an insulator under the dark condition may become a semiconductor under light - an emerging material feature that can promote the development of sensors and memory and computing components.

"This award is a recognition of the collective efforts of colleagues in the American Ceramic Society," says Yang Bai. "I am grateful for the support of the University of Oulu and the European Research Council. It is especially rewarding to receive this recognition while our latest work is opening new opportunities for understanding and engineering photoresponsive functional materials for energy and sensing applications."

Ferroelectric oxides have attracted increasing interest for applications ranging from energy harvesting and sensing to next-generation computing components. However, the mechanisms governing the interaction between light, charge carriers and crystal lattices remain incompletely understood.

In the newly published Applied Physics Letters paper, Bai and collaborators from Japan, USA, Germany and Australia demonstrate that temperature-dependent photoconductivity measurements can be used as an electrical probe of electronic states in Sn-doped barium titanate (BaTiO3), one of the most widely studied ferroelectric materials.

The study reveals how charge carriers respond differently to photons of different energies, providing insight into the interplay between localized polaronic states and more delocalized electronic states. The findings suggest that optical excitation can be used to selectively access different conduction pathways, offering a new route for understanding photoresponse mechanisms in functional oxides.

"Our results show that photoconductivity is more than a detector signal," Bai explains. "It can serve as a powerful, widely applicable experimental tool to facilitate fundamental understanding of how charge carriers interact with crystal defects, lattice vibrations and electronic states in complex materials that go beyond the capability of computation."

Yang Bai's research team focuses on photoferroelectrics, functional ceramics and energy harvesting materials. Previous studies by the team have explored bandgap engineering, bulk photovoltaic effects and filterless photodetection in ferroelectric oxides. The newly published work extends this research direction by linking optical response directly to fundamental charge-transport processes.

According to Bai, understanding these mechanisms is essential for developing future generations of intelligent sensors, energy and computing devices, and light-responsive electronic systems.

"Ferroelectric materials possess a unique combination of optical, electrical and structural functionalities," says Bai. "By understanding how these properties interact, we can create entirely new opportunities for advanced information technologies and electrical systems."

The research article published in Applied Physics Letters. https://doi.org/10.1063/5.0352658

Yang Bai’s researcher profile: https://www.oulu.fi/en/researchers/yang-bai

Yang Bai’s project webpage: https://www.oulu.fi/en/projects/unification-best-piezoelectric-and-photovoltaic-properties-single-photoferroelectric-material