Theorists propose new approach to electroluminescent cooling that works like inverted solar photovoltaic cells

In a study appearing in PRX Energy, researchers propose a way to improve the performance of electroluminescent cooling by using multilayer semiconductors. The approach, called a multijunction configuration, is already used in some special photovoltaic solar cells.

Electroluminescence is the phenomenon behind how LEDs work. It involves adding charge carriers, either electrons or holes, to a semiconductor. This changes the semiconductor’s properties, including how it conducts or insulates against the movement of electrical charges.

In an LED, the charge carriers cause the semiconductor to emit photons of light. This emission can require more energy than is present in the semiconductor. If this is the case, the excess energy to make light comes from heat around the semiconductor. The result—a semiconductor can cool down by emitting light.

Electroluminescent cooling is the reverse of photovoltaics. The emitted photon energy equals the amount of electrical energy supplied to the semiconductor plus the removal of heat from the semiconductor’s surroundings. In photovoltaics, scientists know that multijunction configurations can improve semiconductor efficiency. However, researchers have not previously explored multijunction configurations for electroluminescent cooling.

The researchers conducted a theoretical analysis of cooling power in electroluminescent cooling systems. They used a case study featuring a double-junction structure with gallium arsenide and indium phosphide semiconductor materials. The system consisted of multiple semiconductor layers with different band gaps and low-pass energy filters placed between the layers.

Every semiconductor layer was connected to the cold reservoir and emitted photons toward a black body that served as a hot reservoir. External electrical power was provided by applying a voltage to each semiconductor layer.

The study shows that the combination of these layers results in performance levels that are unattainable by using each layer individually. One key discovery was that for a given cooling power density, increasing the number of semiconductor layers can lower the operating voltage of each layer, leading to an improved coefficient of performance.

The proposed cooling system highlights the potential of solid-state cooling devices. This work also improves scientists’ understanding of the physics underlying these systems.