Tuning the electrical and optical properties of Gd1-xCaxBaCo2O5+δ (x = 0–0.5) using solar energy

• The solar absorption properties of GdBaCo2O5+δ can be improved by Ca doping.
• Gd0.8Ca0.2BaCo2O5 shows ultrafast conductivity transition induced by solar energy.
• Gd0.8Ca0.2BaCo2O5 exhibits low thermal radiative properties at high temperature.

This study reveals that the use of a Ca dopant can increase the solar absorption of GdBaCo2O5+δ, with an optimal composition of Gd0.8Ca0.2BaCo2O5 achieving 85% solar absorptance. Electrical conductivity measurements revealed that this composition allows for faster insulator-metal transition and higher conductivity, with the observed variation in conductivity with 0.8 W/cm2 of solar illumination explained in terms of a first-order spin-state transition. Thermal radiation imaging confirmed that regions of different radiative temperature are related to a change in free carriers that promote scattering, and therefore, cause an increase in infrared reflection. This rapid electrical conductivity transition and the low infrared radiation properties at high temperatures strongly suggest that Gd0.8Ca0.2BaCo2O5 could be used in a variety of potential fields, such as high-temperature thermosensitive or thermal storage materials.

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