Broadband phototransistors realised by incorporating a bi-layer perovskite/NIR light absorbing polymer channel

High performing ultraviolet (UV) to near infrared (NIR) light broadband phototransistors (PTs) are realised by incorporating a bi-layer methylammonium lead triiodide (MAPbI3) perovskite/NIR light absorbing diketopyrrolopyrrole-dithienylthieno[3,2-b]thiophene (DPP-DTT) polymer channel. The bi-layer MAPbI3/DPP-DTT channel has the advantages of the (1) complementary absorption and (2) high charge transport efficiency of the two materials. The on- and off-state transfer characteristics of the bi-layer MAPbI3/DPP-DTT channel PTs, in the presence of different intensities of UV, visible and NIR light, were analyzed. The bi-layer MAPbI3/DPP-DTT channel PTs possess simultaneously a specific detectivity (D∗) of >109 Jones over the UV to visible light wavelength range and a high D∗ of >107 Jones over the NIR light wavelength range. The broadband PTs can be operated at a low voltage (-1 V) without showing persistent photoconductivity behavior. The results are very encouraging. It is anticipated that the bi-layer perovskite/NIR light absorbing polymer channel concept is a very promising approach for realising high performance UV to NIR light broadband PTs.