This new fabric would need to be the outer layer of a garment to receive light, so no insulation and no layering. Most of the heat would not be warming you up. Seems kinda useless?
I would be more interested in a fabric that cools down under the sun.
Don’t all fabrics already absorb IR and heat up?
Through the incorporation of a modest amount (as little as 0.5%) of photothermally active polyaniline (PANI) and polydopamine (PDA) nanoparticles, this fiber exhibits exceptional photothermal conversion performance compared to pure thermoplastic polyurethane (TPU) fiber. Notably, when exposed to 600 W m−2 irradiation for 600 s, the equilibrium temperature of the photo-thermochromic elastic fiber rises impressively from the ambient 20.0 °C to 53.5 °C.Might be good for daytime heating of a tent?