Breaking symmetry to boost solar cell performance

Breaking symmetry to boost solar cell performance
by Riko Seibo
Kyoto, Japan (SPX) Jun 26, 2025

Researchers at Kyoto University have unveiled a novel approach to overcoming long-standing limitations in solar cell efficiency by tapping into an advanced quantum process known as the bulk photovoltaic effect. This effect, distinct from conventional photovoltaic mechanisms, allows current generation beyond traditional voltage limits-but its underlying physics have remained largely elusive.

The phenomenon involves shift current, a steady electrical flow resulting from asymmetric electron excitation. It emerges in systems lacking space-inversion symmetry. When time-reversal symmetry-where physical processes remain unchanged if time flows backward-is also broken, such as in magnetic materials, additional photovoltaic effects may be triggered. These effects, however, have yet to be fully explored.

To investigate, Kyoto University's team engineered an artificial heterostructure combining a monolayer 2D semiconductor with a magnetic layered material. This device emulates broken spatial and time-reversal symmetries at the interface, enabling the study of new optical and electronic behaviors.

By applying external magnetic fields to manipulate temperature and spin orientation, the team measured current-voltage characteristics under light exposure. Their data revealed a new bulk photovoltaic effect called magnetic-injection current, positioning this heterostructure as a strong candidate for next-generation solar technologies.

"Spatial and time-reversal symmetry can be flexibly controlled by artificial structures, enabling a variety of optical responses and current generation that have not been seen before," said corresponding author Kazunari Matsuda.

Critically, the team demonstrated that magnetic-injection current can be tuned via magnetic fields, potentially unlocking innovations across not just solar energy, but also spintronics, optical sensing, and energy-harvesting technologies.

Moreover, the coexistence of shift current and magnetic-injection current opens the door to creating more efficient and multifunctional photovoltaic devices than previously thought possible.

"Our research shows there is great potential in magnetic systems for the development of next generation solar-cells," Matsuda added.Research Report:Nonlinear photovoltaic effects in monolayer semiconductor and layered magnetic material hetero-interface with P- and T- symmetry broken system