Low‐Bandgap Terpolymers for High‐Gain Photodiodes with High Detectivity and Responsivity from 300 nm to 1600 nm

Abstract Three strong electron‐withdrawing monomers and one electron‐donating monomer were chosen by design to impart some desirable properties to the target terpolymers (P1‐P3) for use in the photodiodes, such as strong donor‐acceptor charge transfer, low bandgap, high mobility and good film morphology. Photodiodes with a device structure of ITO/ZnO/active layer/BCP/Al exhibited a significant increase of EQE only under forward bias. In particular, the P2‐based device had the specific detectivity greater than 10 13 Jones from 330 nm to 1060 nm and 10 11 Jones from 300 nm to 1600 nm under 0.5 V and linear dynamic range over 100 dB under 2.0 V. In comparison, after the UV light treatment to the ZnO layer, the P2‐based photodiodes exhibited a high gain in photocurrent under both forward and reverse bias and had specific detectivity above 10 13 Jones at 320–1140 nm, 10 12 Jones at 300–1460 nm and 10 11 Jones at 300–1600 nm under 0.5 V. Our work has firstly demonstrated that high gain and high detectivity in polymer photodetector could be readily achieved under forward bias without the UV light treatment.