One of the main challenges for most solar pyroelectric technology lies in the limited thermal fluctuation harvesting. Unlike any other pyroelectric scheme, this novel design deviates from the conventional by deliberate channeling of the reflected near-infrared heat onto pyroelectric material so as to offer a recurring chance of heat propagation (photon recycling), resulting in an enhanced solar pyroelectric output.
Specifically, a metamaterial is coated on the indoor side to meet the strict cooperative demands for heat reflection, visible transmission, and also UV absorption for respective cooling, transparency, and photocatalysis, while the pyroelectric film is coated on the other side to harvest the reflected waste heat and solar insolation fluctuation for electric power output.
Using the photonic nanostructure approach, flexible tunability in strong suppression of waste heat uptake and nonconflicting enhanced thermal harvesting that operate reliably at ambient outdoor condition can be realized.
The team's theoretical simulations on the influence of the back reflected light on solar pyroelectric conversion testify the appreciable gain in temperature and electric potential distribution.
To demonstrate the effectiveness of their design, the team demonstrted real outdoor solar reflective cooling up to 4.2°C and maximum pyroelectric Voc of -126.5 nA and Isc -32.2 V.
"Our work offers conceptual and technological possibilities for broad implications in other solar optical and heat manifestations such as photovoltaic/thermophotovoltaics, thermoelectric energy conversion, nanoscale heat management, photodetectors, smart window, optical data storage, etc.," the authors conclude.