Back-of-the-napkin:

> 90-nm ultra-thin

I don't know the density, but let's say 2g/cm³. That means a 1cm² piece of this film weighs 18 micrograms.

> 30°C to 150°C in 30 seconds

If by "sunlight" they mean 1000 W/m², which is generous, then our 1×1 piece would catch 0.1 W. Over 30 seconds, that makes 3 joules.

3 joules to heat 18 micrograms by 120 degrees – that's a specific heat capacity of 1.388 joules per gram and K (a bit more if the density is lower than 2, a bit less if it's higher). So: a bit more than typical metals, probably, but not by much.