Ultrafast Charge Transfer in Two-dimensional Janus Heterostructure for Photoconversion

Abstract

The high-throughput density functional theory (DFT) calculation combining with machine learning approach has been an effective technique to establish potential two-dimensional (2D) heterostructure, which have presented potential application in photocatalysis and solar cells. However, the solar energy conversion efficiency strongly depends on the separation of photogenerated electron-hole pairs and increasing the lifetime of charge carriers. Here, taking Al2STe/Al2SSe and SeInAlS/SeGaAlTe heterostructures screened by high-throughput DFT as typical examples, we investigate the interfacial charge transfer dynamics using ab initio nonadiabatic molecular dynamics (NAMD) simulation. The present results demonstrate that the ultrafast hole transfer takes within 16 fs and electron transfer occurs slowly with 1.53 ps for Al2STe/Al2SSe heterostructure. In contrast, the electron transfer completes quickly within 165 fs with hole transfer suppressed for SeInAlS/SeGaAlTe system. Further analysis shows that the ultrafast interlayer charge transfer is dominated by the strong electron-phonon (e-ph) coupling induced by strong orbital hybridization together with coherent vibration of phonon excitation, not the band edge positions commonly considered as the criteria during the high-throughput DFT calculation to determine the performance of photocatalysis and solar cells. Hence, we propose that the high-throughput DFT calculation combined with NAMD simulation is the essential and effective method to design high-performance functional material based on 2D vdW heterostructure and improve the photoconversion efficiency.