A new kind of polymeric semiconductor comprising a micrometer-sized assembly of alkylated-C60 derivatives and carbon nanotubes is constructed in this work as an indicator of temperature rise resulting from the photothermal conversion of carbon nanotubes under near-infrared laser irradiation. Under such conditions, the local heating of this assembly in air reaches temperatures in excess of 220 °C, which would prove very useful for wide applications utilizing the photothermal properties of carbon nanotubes.