A self-powered photodetector based on a CH₃NH₃PbI₃ single crystal with asymmetric electrodes

Methylammonium lead iodide perovskite (MAPbI₃) has made a re-entry into the literature nowadays for its extraordinary characteristics, such as high absorption of light, long carrier diffusion length, high carrier mobility, low trap-state density, low surface recombination velocity and ease of attainment. Here, we report a self-powered photodetector based on a CH₃NH₃PbI₃ single crystal by employing asymmetric Au-Al electrodes. The key issue of this photodetector was the metal-semiconductor contacts, owing to the Schottky junction between them. By setting the channel length between the Au-Al electrodes to 30 μm for sufficient electron-hole pair separation and transportation, the device showed good performance under 1 sun illumination. The short-circuit photocurrent density and open-circuit voltage were 6.86 mA cm^-2 and 0.7 V, respectively. The photocurrent was almost 2 orders of magnitude larger than that based on a perovskite polycrystalline film with a similar device structure. More importantly, the device could detect the lowest noticeable incident power density down to 1 × 10^-8 W cm^-2. Under this weak light intensity, the responsivity was as high as 0.24 A W^-1 without any bias. The photoresponse also had a broadband ranging from 375 nm to 808 nm accompanied by a fast response speed.