Passivation of defects by tetrafluoroterephthalonitrile introduced into MAPbI3 for high-performance perovskite photodetectors†

Methylammonium lead iodide is widely used in the preparation of photodetectors because of its excellent photovoltaic properties. However, because of the nature of the perovskite polycrystals, the low-temperature solution treatment approach of creating perovskite thin films causes flaws to arise in the material. Undercoordinated lead ions (Pb²⁺) have been shown to have comparatively low formation energies among all defect species and to be a major contributor to defect creation. Here, we use a straightforward but efficient additive engineering strategy to introduce tetrafluoroterephthalonitrile as an additive into the perovskite precursor solution to passivate perovskite defects and improve the quality of perovskite thin films for the production of high-efficiency perovskite photodetectors. We demonstrated that –CN (cyano) and polyfluorine atoms in the structure of TFTPN may passivate defects caused by lead ions and prevent the releasing of organic cations (MA⁺), improving the stability of the perovskite structure and the quality of perovskite films. Consequently, we designed perovskite photodetectors with TFTPN that demonstrated exceptional performance in terms of photoresponse, detection and other areas. These devices had a maximum peak external quantum efficiency (EQE) of 91.73%, a lower dark current density of 8.86 × 10⁻¹¹ A cm⁻², a linear dynamic range (LDR) of 105.4 dB, and more. Furthermore, the perovskite photodetector's durability is enhanced by the addition of TFTPN, and after 20 days of storage in an air environment at 25 °C and 20–30% relative humidity, the device retains its original efficiency of 92.3%.