Ultrafast charge transfer in two-dimensional Janus heterostructures for photoconversion

Abstract

Two-dimensional Janus van der Waals (vdW) heterostructures present potential applications in photocatalysis and photovoltaics. However, their solar energy conversion efficiency strongly depends on the separation of their photogenerated electron–hole pairs and the increased lifetime of their charge carriers. Herein, Al₂STe/Al₂SSe and SeInAlS/SeGaAlTe heterostructures, which were selected as typical examples from high-throughput screening results, were investigated for their interfacial charge transfer dynamics using ab initio nonadiabatic molecular dynamics (NAMD) simulation. The results of this study demonstrate that ultrafast hole transfer occurred within 16 fs and electron transfer occurred slowly within 1.53 ps for the Al₂STe/Al₂SSe heterostructure. In contrast, electron transfer completes quickly within 165 fs with the suppression of hole transfer for the SeInAlS/SeGaAlTe system. Further analysis showed that this ultrafast interlayer charge transfer is dominated by strong electron–phonon (e–ph) coupling induced by strong orbital hybridization, together with coherent vibration of phonon excitation, rather than the band-edge positions, which are commonly considered the key criteria in high-throughput density functional theory (DFT) calculations for determining the performance of photocatalysis and solar cells. Hence, we propose that high-throughput DFT calculations combined with NAMD simulation are an essential and effective method for designing high-performance functional materials based on two-dimensional vdW heterostructures and improving their photoconversion efficiency.