Thia[5]helicene-Based D−π–A-type Molecular Semiconductors for Stable and Efficient Perovskite Solar Cells: A Theoretical Study

Abstract

Development of ideal small-molecule hole-transporting materials (HTMs) is one of the most effective means to improve the performance of perovskite solar cells. Meanwhile, the theoretical chemistry method is an efficient pathway to optimize the molecular structure and to probe the structure−property relationship. To further find new HTMs, thia[5]helicene and its counterpart perylothiophene are introduced into the D−π−A-type molecular scaffold of MPA-BT-CA, and the results show that helicene-type HTMs (SM46 and SM48) exhibit obvious advantages in comparison with that of the planar SM45 and SM47. The matched energy levels with the mixed perovskite provide a precondition for the easy hole transfer at the interface, and the blueshifted adsorption spectra can effectually decrease the optical competition between the perovskite and HTMs. More importantly, the helicene-type HTMs show the higher mobilities than that of the planar counterparts, which is mainly contributed by the enlarged hole transfer integrals via compact molecular stacking. Fluorine addition can also stabilize the highest occupied molecular orbitals and enhance the hole transport ability of HTMs. Moreover, a simplified adsorption model for the MPA-BT-CA is constructed to investigate the interfacial properties of adsorbed systems, and the results demonstrate that bidentate adsorption displays more stable adsorption configuration and a better passivation effect for the iodine-vacant FAPbI 3 surface. In summary, this work provides useful clues for the design of new D−π−A-type HTMs, and two promising helicene-based HTMs are proposed.

Donor engineering of a benzothiadiazole-based D–A–D-type molecular semiconductor for perovskite solar cells: a theoretical study

“…To reduce the computational cost, only the adsorbed systems of FAPbI 3 /YN1 and FAPbI 3 /SM37 are investigated in this work. As reported, 13,56 the PbI 2 -terminated FAPbI 3 (100) surface was chosen. The configurations of the optimized systems and corresponding adsorption energies are shown in Fig.…”

“…4–6 Among the various HTMs, small molecule HTMs have been largely synthesized to construct durable and cost-effective cell devices. 7–14…”

Molecular Engineering of Anthracene Core-Based Hole-Transporting Materials for Organic and Perovskite Photovoltaics

“…These acceptor groups (AL1–AL7) are electron-deficient, allowing for better charge separation and reducing recombination loss, and thus are helpful in improving the photovoltaic performances of the optoelectronic devices. Moreover, these groups also have higher conjugation and electron affinity, which is greatly beneficial in separating HOMO and LUMO in designed molecules. – After this, all designed (AS1–AS7) compounds are explored with DFT and time-dependent theory and compared with the R (reference molecule); parameters like photovoltaic, optical and electronic properties, open circuit voltage, frontier molecular orbital (FMO), binding, reorganizational (λ e and λ h ) and excitation energies, light harvesting efficiency, transition density matrix (TDM), and density of states (DOS) have been studied. Furthermore, a detailed study is carried out to examine the charge mobilities from the donor part toward the acceptor unit to suggest that the proposed molecules might be good options for highly efficient OSCs.…”

Precise Modulation of Stable 2D/3D Multidimensional (PEA)2PbBr4 Nanosheets via Post Cation Exchange

“…Metal halide perovskites have attracted considerable attention due to their outstanding optoelectronic properties, , such as high quantum yield, high carrier mobility, and precise bandgap control . These properties have led to their widespread applications in solar cells − and LED lighting − and sensing. − Compared to 3D (three-dimensional) perovskites, 2D Ruddlesden–Popper perovskites (RPP) have a unique internal structure where large organic cations act as interface between the layers . This organic–inorganic–organic alternating layered 2D structure effectively prevents the ingress of water and oxygen, significantly increasing the stability of the perovskite structure.…”