Search

The study explores carbazole‐based organic molecules as transport layers in durable perovskite solar cells, focusing on their optoelectronic and charge transfer properties. Thirteen carbazole derivatives are systematically analyzed via density functional theory (DFT) calculations to understand their structure and optoelectronic characteristics. Substituents like bromo, phenyl, thiophenyl, and pyridyl at positions 3,6‐ and 2,7‐ of carbazole were studied. Phenyl and thiophenyl substitutions lowered highest occupied molecular orbital (HOMO) energy levels, while bromo and pyridyl increased them, tuning HOMO energies from −5.45 to −6.03 eV. These energies align well with perovskite materials valence bands, with absorbance primarily below 400 nm, complementing perovskite absorption. The compounds showed high light‐harvesting efficiencies (LHEs) (0.22 to 0.94) and improved radiative lifetimes. Theoretical investigations identified most compounds as effective p‐type hole‐transport materials (HTM), except 3,6‐ and 2,7‐dithiophenyl carbazoles, which exhibited n‐type behavior due to low hole reorganization energies. Overall, the study highlights computational design's role in developing carbazole derivatives as promising charge carrier precursors for perovskite solar cells. [ABSTRACT FROM AUTHOR]

• DFT and TD-DFT modelling and extensive analysis of eight carbazole-based molecules as HTMs in perovskite solar cells. • Deep HOMO energy levels guarantee proper alignment with the perovskite material. • Acceptor core groups enhance charge transport properties. • Flatness is beneficial when the core consisted of two cycles, particularly for MP 2 P 2 M. • MP 2 P 2 M is distinguished by its superior charge transfer properties. This study mainly focuses on DFT and TD-DFT modelling and extensive analysis of eight carbazole-based molecules (MM, MPM, MP 2. 5 M, MP 2. 6 M, MP 3. 5 M, MPPM, MP 2 P 2 M, and MP 3 P 3 M) as Hole Transporting Materials in Perovskite Solar cells. These compounds have in common the arm N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine (M) characterized by its strong ability to carry holes, low cost, and good stability. The molecule MM presents two arms without acceptor core, while other compounds present two arms separated by different acceptor cores: phenyl, biphenyl, pyridine or bipyridine. All under-probe compounds were favored candidates for HTMs in perovskite solar cells due to their excellent HOMO delocalization, reduced hole reorganization energies, lower chemical reactivity, longer radiative lifetimes, and spontaneous solvation processes. Flatness proved beneficial when the core consisted of two cycles, particularly for MP 2 P 2 M. The results showed that the HOMO levels were primarily influenced by M fragments in most of the molecules, while the LUMO levels were distributed across both the carbazole units and the cores. All molecules exhibited a more stable LUMO compared to that of Spiro-OMETAD, with MP 2 P 2 M showing a notably stable level, resulting in a narrower gap. The study found that, except for MP 2 P 2 M, these materials did not interfere with the perovskite layer and effectively filled pores. The incorporation of acceptor core groups improved the conjugation backbone and electronic states, significantly enhancing charge transport properties, particularly in molecules with a double ring structure. Furthermore, adding a pyridine center greatly increased solubility, especially in MP 3 P 3 M, suggesting that acceptor core inclusion benefits the solubility of the investigated HTMs. The use of two rings core was shown to enhance light harvesting efficiency, boost photocurrent generation, and improve charge transfer performance, particularly in MP 2 P 2 M, which is distinguished by its superior flatness, solubility, and charge transfer properties. [ABSTRACT FROM AUTHOR]

• Faster hole-transport rate is expected for all investigated molecules. • High light harvesting efficiency and good infiltration and pore-filling of HTMs. • MMS1-MMS4 were preferred candidate for HTMs in perovskite solar cells. • MMS4 was the most optimal chemical with remarkable photovoltaic capabilities. This study mainly focuses on modelling and analysis of the reference molecule (M104) as well as four engineered molecules (MMS1-MMS4) as Hole Transport Materials or as light absorbers in Organic Solar Cells. These new molecules are based on thiophene derivatives as acceptor groups, naphthalene as π-bridged groups, and OMeTPA as donor groups. Extensive research was carried out at the molecular level for the studied molecules using DFT and TD-DFT computer simulations to explore their photovoltaic characteristics. All the compounds under investigation were preferred candidate for HTMs in perovskite solar cells because of their superior HOMO delocalization, lower hole reorganization energies, lower chemical reactivity, higher radiative lifetime, higher light-harvesting efficiency, higher dipole moment and spontaneous solvation process inside dichloromethane. The examined molecules' bonded electron-hole pairs can readily split into positive and negative charges to escape coulomb attraction. This increases the short-circuit current density and facilitates hole transport. MMS4 , with its larger maximum absorbance (538.76 nm in dichloromethane), suitable structural features and lower bandgap (2.82 eV), was the most optimal chemical with remarkable photovoltaic capabilities. In conclusion, this work makes a strong case for the synthesis of these high-performing materials by researchers for use in subsequent investigations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The perovskite's VB and CB frontier molecular orbitals are well matched with the three compounds (T 16 , T 17 , and T 18). • The solubility of T 18 is improved by the presence of azomethine groups, which also causes a red shift in the absorption wavelength. • For usage as the active layer of an organic solar cell, T 18 is ideally suited. DFT and TDDFT approaches were used to design three (T 16,17,18) molecules based on 4,4′-dimethoxy-2,2′-bithiophene core to explore the influence of substitution of triphenylamine (TPA) fragment by methoxy groups, and introduction of azomethine π-bridges on the optoelectronic properties of hole transporting materials for perovskite solar cells (PSCs) or as donor for organic solar cells (OSCs). To shed light on the efficiency, stability, and solubility several physicochemical parameters were computed in dichloromethane solvent. All designed molecules show appropriate frontier molecular orbital levels, which facilitates effective hole transfer from the perovskite materials to the HTMs in the hole-transporting layer in PSC devices. They all show good efficiency and pore-fillings and are stable and soluble in dichloromethane. Electron-hole pairs can easily dissociate into free charge carriers, especially for T 16 and T 17 ; consequently, improve short-circuit current densities and facilitate hole transport. It is also advised to use T 18 which includes azomethine bridges as a donor with a non-fullerene Y6 acceptor to create effective OSCs because it exhibits high open circuit voltage, fill factor and low gap energy. [ABSTRACT FROM AUTHOR]

Computational investigations are carried out to design new molecules based on thiophene cores substituted in several positions using different end-capped electron-donating groups formed from triphenylamine or OMe-triphenylamine that can be used as HTMs in Perovskite Solar Cells (PSCs), or as an active layer in Organic Solar Cells. The influence of π-extension on the charge transfer process is also probed by inserting two azomethine groups between acceptor and donor (D-π-A-π-D) moieties. The designed molecules (T 10,12,13,15) were compared with the two synthesized molecules (T 11,14) that have been applied as HTMs in a PSC. Density functional theory (DFT) and time-dependent DFT (TD-DFT) were chosen to calculate different chemical parameters of these molecules. Different chemical parameters were calculated to make the link between geometrical parameters and the efficiency, solubility, and stability of the under-probed compounds. The results show that all molecules can be used adequately with the perovskite matrix because of their sufficient deep HOMOs levels. The optoelectronic properties of the D-A-D molecules show no competition with the light-harvesting of the perovskite layer, while D-π-A-π-D compounds show a slight overlap with the absorption band of perovskites. All molecules indicate a faster hole-transport rate and an easy electron-hole pairs dissociation into free charge carriers, which facilitates the hole transport and enhances open-circuit voltage. Adding a second thiophene unit in the central core reinforces the structure's flexibility and improves Frontier Molecular Orbital's electronic density distribution, while inserting azomethine groups is advantageous for the molecule's solubility. Their short gaps, higher radiative lifetimes, and visible light absorbance make T 12,15 good candidates for their usage in organic solar cell applications. A spontaneous solvation process within dichloromethane for all the investigated molecules was proved based on the high negative free energies. • Faster hole-transport rate is expected for all investigated molecules. • D-A-D molecules do not compete with the light-harvesting of the perovskite layer. • D-π-A-π-D compounds show a slight overlap with the absorption band of perovskites. • The azomethine connection improves the molecule's solubility. • T 12 and T 15 should be good-emitting materials with high efficiency in the OSCs. [ABSTRACT FROM AUTHOR]

In this study, six small carbazole-based molecules are investigated for usage as hole transport materials (HTMs) in perovskite solar cells. Among these compounds, two molecules based on 9-(4-(thiophen-2-yl)phenyl)-9H-carbazole thiophene-phenyle and carbazole (M 1 and M 2) were already synthesized, and four new molecules are designed by substituting carbazole, in positions 3,6 and 2,7, with methoxyphenyl (P 1 and P 2) and dimethoxyphenylamine (E 1 and E 2). Theoretical methods used in the calculations included density functional theory and time-dependent density functional theory. FMOs of all under-probe molecules are well positioned to ensure accurate alignment and prevent charge recombination at the perovskite material interface. The molecules' absorbance in the area below 404 nm shows that HTMs cannot compete with perovskite materials in an inverted configuration of a device. Reorganization energies indicate that M 1 , P 1,2 and E 1,2 are more favourable to be HTM, while M 2 shows a favourable electron transfer; it can be used as an electron transfer material (ETM). The results demonstrate that hole-electron couples can easily separate for any under-exanimated molecules, simplifying hole transport and enhancing the short-circuit (J SC). Additionally, DMPA-based molecules (E 1,2) may display chemical instability because of their poor hardness and the local distribution of charge in electrostatic potential maps. [ABSTRACT FROM AUTHOR]

This study focuses on optoelectronic features of a series of D-A-D molecules composed of thiophene, ethylenedioxythiophene, or 3,4-dimethoxythiophene acceptor groups substituted in several positions using different end-capped electron-donating groups formed from triphenylamine or OMe-triphenylamine. The influence of π-extension on the charge transfer process is probed by inserting two azomethine groups between acceptor and donor (D-π-A-π-D) groups to make them economically profitable like solar cells. The experimental results available in the literature are combined with our detailed B3LYP/6-311G(d,p) study to find relationships between the structural, and optoelectronic properties of molecules and their performance as HTMs or as donors in organic photovoltaic cells. All investigated molecules were preferential competitors for HTMs in perovskite solar cells because of their excellent HOMO delocalization, lower hole reorganization energies, and high light-harvesting efficiency. They all show a spontaneous solvation process within dichloromethane and have larger Stokes shifts with respect to that of spiro-OMeTAD, which is advantageous for the pore-filling of HTMs for PSCs. The bound electron-hole pairs of the studied molecules can easily escape coulomb attraction by dissociating into negative and positive charges, thus facilitating hole transport, and improving the short-circuit current density. D-A-D type molecules have a blue-shifted absorption maximum in the visible light region and consequently have no overlap with the light-harvesting of the perovskite layer. The π-bridges lengthen the electronic conjugation path of the D-π-A-π-D compounds and introduce more flexibility to the molecule's backbone. Their higher radiative lifetimes make them good candidates for their usage in organic solar cell applications. • Faster hole-transport rate is expected for all investigated molecules. • High light harvesting efficiency and good infiltration and pore-filling of HTMs. • D-A-D molecules do not compete with the light-harvesting of the perovskite layer. • The azomethine connection improves the molecule's solubility. • T 3 , T 6 and T 9 should be good-emitting materials with a high efficiency in the OSCs. [ABSTRACT FROM AUTHOR]

In this study, DFT calculations carried out using Carbazole-based HTMs substituted with dimethoxy phenylamine units (DMPA) in positions 2,3,6,7 and 9 are coupled with the experimental results drawn from the literature. The most important challenge for us is to establish a link between the optoelectronic and structural properties of molecules and their performance as HTMs. In this work, we find that the important structural effect is generated by the pyridinic nucleus. The substituents linked to the nitrogen atom of carbazole do not contribute to HOMO or LUMO in most of the studied HTMs. Hence, apart from the illustrated performances, parameters as the contribution of such substituents to being attached to the perovskite, or to the cohesion of the HTM's molecules contributing to the perovskite stability all prove decisive. The 2,7 substitution favors more stabilization of LUMOs when compared to 3,6 substitution, which leads to a narrow gap for 2,7 homologous. This makes these 2,7-substituted molecules good candidates as light absorbent in Organic Solar cells. The differences in the solar cell performances using these HTMs is mostly linked to the effect of these groups on their intermolecular interactions on one hand, and on the interfacial contact between HTMs and perovskite on the other hand. [ABSTRACT FROM AUTHOR]