Near-Unity-Efficiency Charge Transfer and Quantum Confinement-Regulated Long-Lifetime Charge Recombination in 2D...

Transition metal dichalcogenides (TMDs) have shown great potential in optoelectronic devices, such as phototransistors and photodetectors. However, TMD-based optoelectronic devices face notable limitations, primarily weak light absorption due to their atomically thin structure and short exciton-carrier lifetimes caused by strong excitonic effects. Constructing heterostructures (HSs) with TMDs and perovskites is an important strategy to overcome these challenges. Understanding charge transfer dynamics and interlayer recombination at the TMD/2D perovskite interface is essential but still lacking. Here, we prepared monolayer WS₂/2D perovskite HSs with varying n-values (n = 1, 2, and 4, n represents the number of inorganic octahedral layers between two adjacent organic spacers within the 2D perovskite structure) and systematically investigated the photogenerated carrier transfer and interlayer electron-hole recombination process. By employing the n = 1 2D perovskite film and selectively exciting monolayer WS₂, we observed ultrafast photogenerated hole transfer from monolayer WS₂ to the n = 1 2D perovskite film within 200 fs. Further, in the HS formed with the n = 4 2D perovskite film, upon selectively exciting the n = 4 2D perovskite film, we observed an ultrafast photogenerated electron transfer from the n = 4 2D perovskite film to monolayer WS₂, occurring within 2.5 ps. Finally, we found that as the n value increased, the reduced quantum confinement led to a significant increase in the interlayer electron-hole recombination lifetime within the 2D perovskite/monolayer WS₂ HSs, extending from 0.2 ns at n = 1 to 8.6 ns at n = 4. This study demonstrates that in TMD/2D perovskite HSs, ultrafast hole transfer from TMD to the 2D perovskite and efficient electron transfer from the 2D perovskite to TMD can both occur. Additionally, the interlayer electron-hole recombination lifetime can be modulated by quantum confinement effects. Our findings provide critical guidance for optimizing optoelectronic devices based on TMD/2D perovskite HSs.