In this work, we explore the interfacial properties of the C60-Py@MAPbI3 heterojunction of the PbI-terminated MAPbI3(001) surface and pyridine-functionalized C60-Py fullerene derivative through both collinear and noncollinear density functional theory calculations with and without spin–orbit coupling (SOC) effects. C60-Py is bound to the MAPbI3 surface through interfacial Pb–O and Pb–N bonds. Although C60-Py@MAPbI3 is predicted to be the same type II heterojunction at all of the computational levels considered, the SOC effects largely decrease the energy gap of the first conduction bands of C60-Py and MAPbI3, thereby accelerating the interfacial electron transfer. Further dynamics simulations show that the inclusion of the SOC effects induces the transfer of approximately 80% of electrons from MAPbI3 to C60-Py within 1 ps. The work demonstrates that the SOC effects are indispensable for the interfacial properties of C60-Py@MAPbI3 and could also play a non-negligible role in tuning the optoelectronic properties of fullerene-based or similar perovskite devices.

Two-dimensional (2D) perovskites are emerging as promising candidates for diverse optoelectronic applications because of low cost and excellent stability. In this work, we explore the electronic structures and interfacial properties of (4Tm) 2 PbI 4 with both the collinear and noncollinear DFT (PBE and HSE06) methods. The results evidently manifest that explicitly considering the spin–orbit coupling (SOC) effects is necessary to attain correct band alignment of (4Tm) 2 PbI 4 that agrees with recent experiments ( 31712613 Nat. Chem. 2019 11 1151 ; 32350477 Nature 2020 580 614 ). The subsequent time-domain noncollinear DFT-based nonadiabatic carrier dynamics simulations with the SOC effects reveal that the photoinduced electron and hole transfer processes are asymmetric and associated with different rates. The differences are mainly ascribed to considerably different nonadiabatic couplings in charge of the electron and hole transfer processes. Shortly, our current work sheds important light on the mechanism of the interfacial charge carrier transfer processes of (4Tm) 2 PbI 4 . The importance of the SOC effects on correctly aligning the band states of (4Tm) 2 PbI 4 may be generalized to similar organic–inorganic hybrid 2D perovskites having heavy Pb atoms.

Unraveling the charge generation dynamics at the donor–acceptor (D−A) interfaces is crucial for improving the photovoltaic performances of nonfullerene acceptor‐based organic solar cells (OSCs). Herein, time‐dependent density functional theory (TDDFT) based nonadiabatic dynamics simulations are used to explore the ultrafast photoinduced dynamics at a nonfullerene D–A PTB7@PDI interface. Based on the results, it is found that such an interface exhibits distinct charge generation processes upon excitation with different wavelengths. The excitation at ≈591 nm mainly results in the local exciton |PTB7∗>, whereas the charge transfer exciton |PTB7+PDI−> also has minor contribution. Later on, the electron transfer from PTB7 to PDI, i.e., channel I charge generation process, occurs in 1 ps. The situations are much more complex when the excitation is conducted using ≈487 nm light. The initial populated excitons include local excitons |PDI∗>, |PTB7∗>, and charge transfer exciton |PTB7+PDI−>, after which both channel I and channel II charge generation take place ultrafast. However, in both situations, the charge generation processes occur within a few picoseconds, which is consistent with previous experimental work. Such ultrafast charge generation processes in a wide range of solar spectra are one of the reasons responsible for the excellent photovoltaic properties of such OSCs.

Unraveling the photogenerated exciton dynamics of π­stacked molecular aggregates is of great importance for both fundamental studies and industrial applications. Among various π­stacked molecular aggregates, perylene tetracarboxylic acid bisimides (PBI)...

Herein, we employed a developed LR-TDDFT-based nonadiabatic dynamics simulation method that explicitly takes into account the excitonic effects to investigate photoinduced excitation energy transfer dynamics of a double-walled CNT model with different excitation energies. The low E11 excitation of the outer CNT that generates a locally excited (LE) |out*⟩ exciton does not induce any charge separation. In contrast, the E11 excitation of the inner CNT can generate four kinds of excitons with the LE exciton |out*⟩ dominates. In the 500-fs dynamics simulation, the LE exciton |in*⟩, charge transfer (CT) excitons |out-in+⟩ and |out+in-⟩ excitons are all gradually converted to the |out*⟩ exciton, corresponding to a photoinduced excitation energy transfer, which is consistent with experimental studies. Finally, when the excitation energy is close to the E22 state of the outer CNT (~1.05 eV), a mixed population of different excitons, with the |out*⟩ exciton dominated, is generated. Then, the photoinduced energy transfer from the outer to inner CNTs occurs in the first 50 fs, which is followed by an inner-to-outer excitation energy transfer completed in 400 fs. The present work not only sheds important light on the mechanistic details of wavelength-dependent excitation energy transfer of a DWCNT model, but also demonstrates the roles and importance of the CT excitons in photoinduced excitation energy transfer. On the other hand, it also emphasized that explicitly including the excitonic effects in electronic structure calculations and nonadiabatic dynamics simulations is significant for either correct understanding or rational design of optoelectronic properties of periodically extended systems.