Schottky Barrier-Controlled Black Phosphorus/Perovskite Phototransistors with Ultrahigh Sensitivity and Fast Response

Phototransistors are recognized as highly sensitive photodetectors owing to their high gain induced by a photogating effect. However, the response speed of a typical phototransistor is rather slow due to the long lifetime of trapped carriers in the channel. Here, a novel Schottky barrier-controlled phototransistor that shows ultrahigh sensitivity as well as a fast response speed is reported. The device is based on a channel of few-layer black phosphorous modified with a MAPbI_3−xCl_x perovskite layer, whose channel current is limited by the Schottky barrier at the source electrode. The photoresponse speed of the device can be tuned by changing the drain voltage, which is attributed to a field-assisted detrapping process of electrons in the perovskite layer close to the Schottky barrier. Under optimal conditions, the device exhibits a high responsivity of 10⁶–10⁸ A W⁻¹, an ultrahigh specific detectivity up to 9 × 10¹³ Jones, and a response time of ≈10 ms.