Self-encapsulating Ag nanospheres in amorphous carbon: a novel ultrathin selective absorber for flexible solar-thermal conversion

Abstract

Solar-thermal conversion is very appealing for various applications, especially in wearable energy conversion devices. Despite various solar absorbers having been developed, they are usually suitable only for rigid substrates. Hence it remains a great challenge to design an ultrathin absorber on flexible substrates for emerging wearable applications. Here, it is demonstrated that Ag nanospheres spontaneously encapsulated in amorphous carbon (ANEAC) can dramatically enhance light absorption, leading to an impressive solar-thermal conversion efficiency of 87% with a whole thickness of only approximately 130 nm. Due to the intriguing ultrathin feature, these ANEAC absorbers can be universally deposited on flexible substrates, including polyimide, polyethylene terephthalate, textiles, etc. The surface temperature exceeds 94 °C under 1 kW m⁻² (1.0 Sun) irradiation for ANEAC on cotton textiles, which is better than that for a common flexible absorber. More importantly, ANEAC absorbers possess superior mechanical robustness, and the surface temperature is always above 75 °C under 1.0 Sun irradiation after serious stretching, abrasion, rubbing, and tape-peeling. Surprisingly, the highest surface temperature for a sample stretched 10 000 cycles reaches 86.8 °C after 10 min of irradiation (1.0 Sun). Therefore, these superior properties of ANEAC absorbers show potential applicability in wearable thermal energy conversion.