Effects of the indium tin oxide/perovskite interface on the photocurrent amplification of perovskite photodetectors

Perovskite photodetectors processing a photocurrent amplification have attracted much attention due to their high response to light illumination and have been exploited in a regular device geometry. Here, photocurrent amplification is demonstrated in an inverted perovskite photodetector, and the effect of the indium tin oxide (ITO)/perovskite interface on the photocurrent amplification factor are exploited. It is found that the photocurrent amplification is limited by the ITO/perovskite interface, which can be proved by the devices with bare ITO, Cu2O particles partially covered ITO, and poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) fully covered ITO as the anodes. A photocurrent amplification factor of about 27 is demonstrated in the perovskite photodetector with a bare ITO as the anode, which is one of the highest ones among the reported perovskite photodetectors. It also exhibits a maximum response of 4.1 A/W and a detectivity of 10(11) Jones. Compared with the bare ITO device, the photocurrent amplification of the devices decreases gradually with the reduced contact area between ITO and perovskite and eventually disappears when the direct contact is totally removed. The photocurrent amplification is attributed to the long-lived accumulated holes as well as the positively charged CH3NH3+ and I vacancy at the ITO/perovskite interface, which dramatically lowers the injection barrier of electrons and leads to a multiple electron injection.