Interfacial and Molecular Engineering of a Helicene-Based Molecular Semiconductor for Stable and Efficient Perovskite Solar Cells

Abstract

Due to the attractive optoelectronic properties and extensive application in solar cells, the design of new helicene-type molecular semiconductors is of remarkable importance for development of high-efficiency hole-transporting materials (HTMs). In this work, three helicene HTMs are constructed on the basis of the molecular conformation of experimentally reported T5H-OMeDPA by replacing the thia[5]­helicene unit with a more curved π-linker of dithia[6]­helicene and considering the effects of fluorine substitution. The electronic and optical properties, hole transport, and interfacial property are studied with quantum chemistry methods, and the results show that new tailored HTMs perform much better than T5H-OMeDPA in terms of the calculated HOMO levels, hole mobility, optical adsorption, solubility and stability, interfacial stability, and hole transfer. The more stable HOMO levels of new HTMs (SM31–SM33) will be beneficial for the regulation of interfacial energy alignment. Importantly, the hole mobilities of the designed HTMs are also distinctly improved due to the enhanced electronic coupling and lowered hole reorganization energies. The fluorine substitution can clearly heighten the orbital overlapping via compact molecule packing. In the meantime, dithia[6]­helicene can lower the reorganization energy although the more curved π-electron system often disturbs the intermolecular π–π stacking. Moreover, our results also reveal that additional Pb–S interactions can effectually promote the interface adsorption and hole extraction. In sum, our study shows the validity of fluorine substitution and introduces helicene with a more extended structure, and three potential helicene-type HTMs are proposed.

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

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

Organic fluorophore-substituted polyaza-[7]helicenes derived from 1,10-phenanthroline: Studying the chromophoric effect on fluorescence efficiency

“…Push-pull azahelicenes have been relatively rare in scientific literature; however, they have recently received significant attention owing to the unique combination of improved chirality and the essential properties of delocalized p-electron units prepared with D and/ or A units. [13][14][15] Several research groups have made progress in their synthesis and applied them in various fields, such as dyesensitized solar cells, 16 circularly polarized luminescence, 17 self-assembly, 18 perovskite solar cells (PSCs), [19][20][21][22][23][24] and organic light-emitting diodes (OLEDs). 25 To illustrate the most recent achievements in aza-helicenes (Fig.…”

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.…”