LAUSR

Abstract Self-powered ultra-broadband photothermoelectric photodetectors based on free-standing reduced graphene oxide (RGO) films annealed under various temperatures (200–1000  °C ) are developed for the first time. The preparation process of the free-standing RGO films is simple, low-cost, and scalable. An interesting phenomenon was found that with increasing annealing temperature, responsivities of RGO-based photodetectors decreased across the ultra-broadband range from ultraviolet (375 nm) to terahertz (118.8 μm) regions. The dependence of device responsivity on annealing temperature is derived from differences in the oxygen functional groups present on the RGO films. The negative sheet Hall coefficients of the annealed RGO films confirmed that they behaved as n-type semiconductors, indicating that electron-donating groups dominated in all the annealed free-standing RGO films. The content of electron-donating groups gradually decrease as the annealing temperature rose. The response times of our devices (