Rational design of monolayer transition metal dichalcogenide@fullerene van der Waals photovoltaic heterojunctions with time-domain density functional theory simulations.

van der Waals heterojunctions formed by transition metal dichalcogenides (TMDs) and fullerenes are promising candidates for novel photovoltaic devices due to the excellent optoelectronic properties of both TMDs and fullerenes. However, relevant experimental and theoretical investigations remain scarce to the best of our knowledge. Herein, we have first employed static density functional theory (DFT) calculations in combination with time-domain density functional theory (TDDFT) based nonadiabatic dynamics simulations to rationally evaluate the photovoltaic performances of four TMD@fullerene heterostructures, i.e. WSe2@C60, WSe2@C70, MoTe2@C60 and MoTe2@C70, respectively. Our simulation results indicate that the C70-based heterostructures overall have better photoinduced electron transfer efficiencies than their C60-based counterparts, among which the performance of the WSe2@C70 heterostructure is the best and the electron transfer from WSe2 to C70 almost accomplishes within 1 ps. In addition, the large build-in potential of about 0.75 eV of WSe2@C70 is beneficial for the charge separation processes. Our present work not only selects the van der Waals TMD@fullerene heterojunctions that might have excellent photovoltaic properties, but also paves the way for the rational design of novel heterojunctions with better optoelectronic performances with DFT and TDDFT simulations in the future.