Indian researchers surpass a century-old barrier in converting heat into electricity

Scientists in India have found a method to produce an exceptionally large electrical voltage from a very small temperature difference, calling into question a limit that has shaped how crystalline solids are understood for more than 100 years.

The advance relies on a specially designed semiconductor made from scandium nitride (ScN).

A team from the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), the University of Sydney and the Indian Institute of Science reports that this material can generate a thermoelectric voltage well beyond what had long been considered achievable in crystalline solids.

HOW DOES HEAT MAKE ELECTRICITY?

The result stems from the Seebeck effect.

Put simply, if one side of a material is warmer than the other, mobile charge carriers can drift in a way that creates an electrical voltage.

This principle is already used in technologies such as temperature sensors and systems that harvest electricity from waste heat.

For many years, researchers assumed there was a practical upper bound on the voltage that a temperature gradient could produce in a crystalline solid.

The new work disputes that long-standing view.

The team fabricated thin ScN films and intentionally added magnesium. This changed the way charges move through the crystal, creating what the scientists describe as a heavily doped, highly compensated semiconductor.

The outcome was striking.

In one film, the researchers recorded a Seebeck coefficient above -124.6 millivolts per kelvin near room temperature—almost 100 times higher than the previously reported ceiling for crystalline solids.

The effect intensified further as the films were made thinner.

HOW CAN THIS INNOVATION HELP?

The discovery could eventually support far more sensitive tools for detecting heat and minute temperature shifts.

The researchers have already demonstrated an early-stage photon sensor based on the material.

When a laser shone on one of the device’s contacts, it produced a small temperature difference that, in turn, generated a measurable voltage.

The prototype delivered a Seebeck response of -102.4 millivolts per kelvin and showed a quick, repeatable signal across multiple trials.

The team says that with further refinement, the approach could help detect extremely weak light—potentially even down to single photons.

The work may also prove useful for ultra-sensitive temperature sensors, thermal imaging, heat-flow monitoring and emerging quantum technologies.

An Indian patent application has been submitted covering thermoelectric thin-film materials and sensors derived from the research.