A High‐Responsivity Photodetector Based on PF ₆ ‐CsPbBr ₃ Quantum Dots Modified MoTe ₂ Ultrathin Film

Although 2D semiconductors with excellent electronic and optical properties are considered as strong candidates for next‐generation photodetectors, the sphotoelectric conversion efficiency of present ultrathin 2D semiconductor is still lower than expected owing to their weak optical absorption. Here, a high responsivity photodetector based on MoTe 2 ultrathin film (5.7 nm) is proposed, which is surface modified by CsPbBr 3 quantum dots (QDs) as an absorbent layer. Compared with pristine MoTe 2 devices, the responsivity of the MoTe 2 /CsPbBr 3 photodetector is up to 42.7 A W −1 at 0.2 V, and the enhancement ratio reaches 5400 times. Furthermore, the process of ligand exchange partially replaces the long organic chains with PF 6 − ions, enabling the MoTe 2 /PF 6 ‐CsPbBr 3 photodetector to achieve a responsivity of up to 165.8 A W −1 at 0.2 V. Due to the reduction in the recombination of photogenerated electron–hole pairs, the responsivity of the MoTe 2 /PF 6 ‐CsPbBr 3 photodetector is 2 × 10 4 times higher than that of pristine MoTe 2 devices. Additionally, thanks to the excellent charge transfer capability of ionic ligands, the response time of the MoTe 2 /PF 6 ‐CsPbBr 3 photodetector accelerates from 11.1 to 1.58 s. This work paves a new way for the further development of high‐performance, low‐cost, and energy‐efficient photodetectors by using QDs modified ultrathin 2D materials.