Harnessing Light for Next-Generation Solid-State Cooling Technologies

Solid-state cooling has the potential to provide a more energy-efficient and environmentally friendly solution compared to traditional refrigeration, which typically depends on thermodynamic cycles using greenhouse gases. However, existing solid-state cooling technologies, which rely on caloric effects (changes in temperature under external fields), face significant challenges that limit their practical use in everyday refrigeration devices.

One major obstacle is that the temperature conditions for operation need to be very close to specific phase-transition points—points where a material's state changes due to changes in temperature or other external factors. If the conditions deviate from these points, the fields required to drive the cooling effect become too strong to be practical. Unfortunately, these phase transitions rarely happen near room temperature, which is critical for most applications. Moreover, the cooling effect tends to occur over a narrow temperature range and diminishes rapidly outside of this range.

In our study, we used advanced simulation techniques to explore an alternative approach: using light to drive phase transitions in specific materials known as polar oxide perovskites. These materials have unique properties that allow them to undergo phase transitions when exposed to light. We found that in the case of the ferroelectric material KNbO₃, this process can generate a large "photocaloric" effect, meaning that the material experiences significant temperature changes (up to 10 K) and heat absorption (around 100 J K⁻¹ kg⁻¹) when exposed to light, across a broad temperature range that includes room temperature.

These results suggest that light-driven phase transitions could provide a more flexible and effective way to achieve solid-state cooling across a wide temperature range, overcoming the limitations of traditional caloric effects. We expect that this phenomenon could also be applicable to other materials with similar properties, opening new avenues for the development of efficient cooling technologies.

Reference: 

Rurali, Riccardo, et al. Giant photocaloric effects across a vast temperature range in ferroelectric perovskites. Physical Review Letters, 133 (11) 116401, 2024.