Transient On/Off Photocurrent Response of Halide Perovskite Photodetectors

Solution-processed photodetectors such as those based on halide perovskite semiconductors show attractive properties for emerging applications in lightweight, transparent, flexible, and spectrally selective optical sensors. The transient photocurrent to a light perturbation often shows a complex response characterized by sharp transient peaks in the photocurrent curves when the stimulus changes or slow rise times depending on features such as the applied voltage or the active layer thickness. We present the characteristic response of halide perovskite photodetectors by measuring the response of a FTO/PEDOT/MAPbBr3/Au device, and we establish a new model for the analysis of the dominant transient shapes. The model uses very basic suppositions of photoconversion to electricity: charge generation, collection, and polarization. These standard properties are combined with a new essential feature: a delayed photocurrent mode that forms a photoinduced chemical inductor. This last property is caused by ionic–electronic interaction phenomena related to the well-known inverted hysteresis of perovskite devices. We show that these elementary properties explain well the varied characteristic time transient currents in on/off voltages and light switching.