Research on heterojunction semiconductor photodetectors based on CsPbBr₃ QDs/CsPbBr_<i>x</i>I_3–<i>x</i> QDs

Abstract All-inorganic CsPbBr 3 perovskite quantum dots (QDs) have attracted extensive attention in photoelectric detection for their excellent photoelectric properties and stability. However, the CsPbBr 3 quantum dot film exhibits a high non-radiative recombination rate, and the mismatch in energy levels with the carbon electrode weakens hole extraction efficiency. These reduces the device's performance. To improve this, a semiconductor photodetector based on fluorine-doped tin oxide (FTO)/dense titanium dioxide (c-TiO 2 )/mesoporous titanium dioxide (m-TiO 2 )/CsPbBr 3 QDs/CsPbBr x I 3– x ( x = 2, 1.5, 1) QDs/C structure was studied. By adjusting the Br – : I – ratio, the synthesized CsPbBr x I 3– x ( x = 2, 1.5, 1) QDs showed an adjustable band gap width of 2.284−2.394 eV. And forming a type Ⅱ band structure with CsPbBr 3 QDs, which reduced the valence band offset between the active layer and the carbon electrode, this promoted carrier extraction and reduced non-radiative recombination rate. Compared with the original device (the photosensitive layer is CsPbBr 3 QDs), the performance of the photodetector based on the CsPbBr 3 QDs/CsPbBr 2 I QDs heterostructure is significantly improved, the responsivity ( R ) increased by 73%, the specific detectivity rate ( D * ) increased from 6.98 × 10 12 to 3.19 × 10 13 Jones, the on/off ratio reached 10 6 . This study provides a new idea for the development of semiconductor tandem detectors.