Sci. Adv. 3, e1602617 (2017)

Although many desirable properties of graphene photodetectors, such as wide bandwidth and spectral response, have been demonstrated previously, the best inorganic photodetectors are still superior in terms of the linearity of their response over a large range of optical powers. To date, the linear dynamic range (LDR) of graphene photodetectors has been limited by thermal diffusion of carriers and other effects, and this has restricted their applications in imaging. Now, Adolfo De Sanctis and colleagues from the UK and Spain have made graphene-based photodetectors that exhibit an LDR of 44 dB, which they note is three orders of magnitude better than previous graphene devices. At the same time, the detectors have a broad spectral response from the ultraviolet-A to the mid-infrared and are sufficiently stable in atmospheric conditions such that encapsulation is not required. The device is made by introducing FeCl3 into the top three layers of four-layer graphene flakes. The FeCl3 in the structure was laser defined by exposing the graphene to intense green laser light (532 nm wavelength with an intensity of 15.3 MW cm−2) by raster scanning 5.5-μm-wide sections for 3 s in 0.5-μm steps.