Melanin–Perovskite Composites for Photothermal Conversion

Biomacromolecular pigments, such as melanin, play an essential role in the survival of all living beings. Melanin absorbs sunlight and transforms it into heat, which is crucial for avoiding damage to skin cells. Light absorption produces excited electrons, which could either fall back to ground states by releasing the heat (photothermal effect) and/or light (photoluminescence), or stay at higher energy levels within its lifetime period, which can be captured through external electronic circuitry (photovoltaic effect). In this study, it is demonstrated that the combination of melanin with halide perovskite light absorber in the form of a composite exhibits high absorbance from the UV to NIR region in the solar spectrum. And the composite displays significantly reduced photoluminescence and minimized density of residual excited states (verified by photovoltaic measurement) owing to the significantly enhanced nonradiant quenching by the melanin. As a result, the composite shows an ultrahigh solar-thermal quantum yield of 99.56% and solar-thermal conversion efficiency of ≈81% under one-sun illumination (AM1.5), which is superior to typical carbon materials such as graphene (≈70%). By coating the photothermal composite film on the hot-side of thermoelectric devices, a 7000% increase in output power as compared to the blank device under illumination is observed.