How Molecular Chirality Controls Photocurrent in 2D Hybrid Perovskites

Controlling how electrical charges respond to light is becoming an increasingly important frontier in advanced photovoltaic and optoelectronic materials. New research from the Institute of Science Tokyo offers an intriguing insight: in two-dimensional organic–inorganic hybrid perovskites (2D-OIHPs), the molecular “handedness” of organic components can determine the direction in which a light-induced photocurrent flows.

The researchers investigated the circular photogalvanic effect (CPGE), where circularly polarized light generates an electrical current that changes direction depending on the light’s helicity. Understanding this effect is particularly challenging because measured photocurrents can originate from both the crystal bulk and its surfaces or interfaces.

The Science Tokyo team addressed this by illuminating the crystals at normal incidence, allowing the bulk response to be distinguished from surface-related effects. The experiments showed that photocurrent emerged perpendicular to the crystal’s spontaneous polarization, while the corresponding response along the polarization direction disappeared—providing evidence of a bulk-origin CPGE.

More significantly, the researchers demonstrated a direct route to controlling this current through molecular chirality. They created crystals using left- and right-handed versions, or enantiomers, of the same organic molecule. Switching between these molecular forms reversed the crystal’s bulk polarity and consequently reversed the direction of the CPGE photocurrent.

The result highlights how molecular-level design can influence macroscopic electronic behaviour in hybrid perovskites. Rather than treating the organic component simply as structural support, the research shows that its chirality can become a functional parameter for engineering polarity and light-driven charge transport.

While the finding does not represent a direct improvement in conventional solar-cell efficiency, it expands understanding of how perovskite materials can be engineered for more sophisticated light–matter interactions. Such control could eventually support helicity-sensitive photodetectors, spin-photonic systems and emerging opto-spintronic devices.