Engineering the Exciton Dissociation in Quantum‐Confined 2D CsPbBr₃ Nanosheet Films

Abstract

Recent years have witnessed a rapid development of all-inorganic halide perovskite in optoelectronic devices. Ultrathin 2D CsPbBr 3 nanosheets (NSs)with large lateral dimensions have demonstrated exceptional photophysical properties because of their analogous exciton electronic structure to quantum wells. Despite the incredible progress on device performance, the photophysics and carrier transportation parameters of quantum-confined CsPbBr 3 NSs are lacking, and the fundamental understanding of the exciton dissociation mechanism is far less developed. Here, a ligands rearrangement mechanism is proposed to explain why annealed NS films have an increased charge transfer rate and a decreased exciton binding energy and lifetime, prompting tunneling as a dominant way of exciton dissociation to separate photogenerated excitons between neighboring NSs. This facile but efficient method provides a new insight to manipulate perovskite nanocrystals coupling. Moreover, ultrathin 2D CsPbBr 3 NS film is demonstrated to have a enhanced absorption cross section and high carrier mobility of 77.9 cm 2 V −1 s −1 , contributing to its high responsivity of 0.53 A W −1 . The photodetector has a long-term stability up to three months, which are responsible for reliable perovskite-based device performance.

Metal halide perovskite nanocrystals and their applications in optoelectronic devices

“…It can be seen that the theoretically calculated E b values of CsPbCl 3 and CsPbBr 3 are greater than the thermal energy value at RT, which indicates that CsPbCl 3 and CsPbBr 3 are optically more favorable. In fact, the relative accuracy of theoretical calculations was confirmed by experimental temperature‐dependent absorption, optical absorption, and magnetoabsorption …”

Graphene, Transition Metal Dichalcogenides, and Perovskite Photodetectors

“…This exciton dissociation mechanism was proposed based on microscopic KPFM results (Figure 9d). As shown in Figure 9e and f, the response and recovery time were short, and the largest responsivity of 0.53 A W −1 could be obtained under the 525 nm irradiation with the intensity of 0.009 mW cm −2 [54].…”

Interface Engineering in n‐i‐p Metal Halide Perovskite Solar Cells

“…XPS is a surface‐sensitive tool that can reveal the chemical compositions of the interface layer . The binding energy of Pb 4f depends on its chemical environment.…”

“…Moreover, the functional molecule and insulating buffer layers can also be confirmed by element characteristic peaks . FTIR spectra can be used to monitor the chemical composition based on the stretching vibrations of chemical bond . The peak at 1567 cm −1 resulted from aromatic CC stretching vibration of PEA + cation, indicating the 2D MHP interface .…”