Red-shifted Absorption Spectra Research Articles

Design of non-fused ring electron acceptors with “embracing-type” side chains for organic solar cells

Backbone planarity is an inherent structural feature for fused ring electron acceptors and one of important prerequisites for their high photovoltaic performance. However, for non-fused ring electron acceptors (NFREAs), it is a challenging task to achieve it. In this work, two NFREAs (Ph2TIC and BT2TIC) containing thiophene-benzene-thiophene or thiophene-benzothiadiazole-thiophene three non-fused aromatic rings in central scaffold were designed with an attempt to use a pair of 2,4,6-triisopropylphenyl substituents (referred as “embracing”-type side chains) at 3,3′-positions of the two thiophene units to lock the backbone in a planar conformation. X-ray crystallography revealed that Ph2TIC has a quasi-planar backbone, whereas BT2TIC shows a twisted one, but both tend to form two-dimensional layered arrays through intermolecular π-π stacking involving terminal acceptor moieties. UV–vis light-absorption spectroscopy showed that both compounds have similar optoelectronic properties either in dilute solutions or in solid film state, thus confirming the conformation-lock function of the “embracing”-type side chains. While for photophysical properties, BT2TIC displays a red-shifted broader light absorption spectrum as compared to Ph2TIC due to the introduction of an additional acceptor moiety in the structure. Ph2TIC and BT2TIC were evaluated as the acceptor materials in organic solar cells in combination with PM6, a typical donor polymer, and delivered the optimized power conversion efficiencies of 4.31 % and 3.78 %, respectively. Although the photovoltaic performances are modest, the work provides a new thought for maintaining the backbone planarity in NFREAs and would be useful in their future design.

Push-Pull Bis-Norbornadienes for Solar Thermal Energy Storage.

The norbornadiene/quadricyclane (NBD/QC) photoswitch pair represents a promising system for application in molecular solar thermal energy storage (MOST). Often, the NBD derivatives have very limited overlap with the solar spectrum, and substitution to redshift the absorption leads to a decrease in the gravimetric energy density. Dimeric systems mitigate this factor because two switches can 'share' a substituent. Here, we present five new NBD dimers with red-shifted absorption spectra. One dimer features the most red-shifted absorption onset (539 nm) and a significantly red-shifted absorption maximum (404 nm) for NBD systems reported so far, without compromising thermal half-life. Promising properties for high-performance MOST applications are demonstrated, such as high absorption onsets reaching 539 nm, and energy densities of 379 kJ/kg, while still maintaining long half-lives of the metastable isomer, up to 23 hours at 25 °C.

Highly efficient donor-acceptor configurated Nicotinaldehyde-based small molecules for NLO materials: Base-free deformylation and DFT study

In the current study, 6-methyl nicotinaldehyde derivatives (MNP-BTMP) were synthesized by using the Suzuki- cross-coupling method which involved deformylation approach. The FTIR, UV–Visible, 1HNMR and 13CNMR spectroscopic analyses were performed to validate the structures of newly synthesized derivatives. Additionally, the density functional theory (DFT) approach at M06/6–311G(d,p) level was utilized in order to calculate their optoelectronic and nonlinear optical (NLO) properties. Consequently, their HOMO-LUMO band gaps (Egap) were obtained in the range of 4.77–5.55 eV. A significant charge transfer from HOMO towards LUMO was investigated which was further supported by DOS. Moreover, they exhibited the maximum absorption wavelengths (λmax) in the UV- Vis region as 269.989–303.496 nm. Among the derivatives, BTMP was found with the least energy gap (4.77 eV) and the red-shifted absorption spectra (λmax =303.496 nm) as compared to other derivatives. Owing to these unique properties, BTMP was also found with significant linear polarizability ⟨α⟩ and hyperpolarizability (βtot and γtot) values i.e., 2.816×10−23, 1.855 × 10−30 and 4.553 × 10−35esu., respectively among the titled compounds. These findings indicated the potential use of these organic derivatives in the NLO applications.

Benzannulated Double Aza[9]helicenes: Synthesis, Structures, and (Chir)optical Properties.

A benzannulated double aza[9]helicene 1 was successfully synthesized via a one-pot oxidative fusion reaction. 1 was derivatized to N-alkylated double aza[9]helicene 1-Et and 1-Bu, whose structures were determined by X-ray diffraction analysis. 1-Et and 1-Bu exhibited red-shifted absorption and fluorescence spectra compared to single aza[9]helicene. The double aza[9]helicenes were expected to have two different conformers. Consistent with solid-state structure, the chiral-isomer was estimated to be more stable by 16 kcal/mol relative to meso-isomer. Indeed, enantiomers of 1-Et and 1-Bu were optically resolved by HPLC and showed mirror-imaged CD and CPL spectra with the CPL brightness up to 19.2 M-1cm-1 for 1-Bu.

Acenaphthylene-Based Chromophores for Dye-Sensitized Solar Cells: Synthesis, Spectroscopic Properties, and Theoretical Calculations.

A set of acenaphthylene dyes with arylethynyl π-bridges was tested for dye-sensitized solar cells (DSSCs). Crucial steps for the extension of the conjugated system from the acenaphylene core involved Sonogashira coupling reactions. Phenyl, thiophene, benzotriazole, and thieno-[3,2-b]thiophene moieties were employed to extend the conjugation of the π-bridges. The systems were characterized by cyclic voltammetry and by UV-vis absorption and emission. The spectroscopic characterization showed that the last three bridges resulted in red-shifted absorption and emission spectra relative to the parent phenyl-bridged compound, in accordance with TD-DFT calculations. The phenylethynyl derivative 6a achieved a conversion efficiency of 2.51% with Voc, Jsc, and FF values of 0.365 V, 13.32 mA/cm2, and 0.52, respectively. The efficiency of this compound improved to 3.15% with the addition of CDCA (10 mM), representing the best efficiency result in this study. The overall conversion efficiency of the other aryl derivatives 6b-d proved to be significantly inferior (14-40%) to that of 6a due to a significant decrease of Jsc.

Impact of end‐capped engineering on the optoelectronic characteristics of pyrene‐based non‐fullerene acceptors for organic photovoltaics

AbstractPyrene‐based molecules are being explored as prospective fullerene‐free acceptors for organic solar cells (OSCs), due to their easy accessibility, structural planarity, and excellent electron delocalization. In this work, we successfully designed and analyzed pyrene‐based acceptor materials (QL1–QL8) to investigate their photophysical and electro‐optical parameters. Various geometric parameters were computed at the MPW1PW91/6‐31G(d,p). Advanced quantum chemical approaches were employed to characterize the molecules. All the tailored molecules (QL1–QL8) exhibit a lower bandgap than the reference (R), signifying their superiority. Among these, QL8 was found to have a maximum absorption (λmax) at 791.37 nm and an optical bandgap (ELUMO − EHOMO) minimum of 2.11 eV. Redshifted absorption spectra are observed in both gaseous and solvent phases for all the designed (QL1–QL8) molecules in contrast to R. Among these, QL4 exhibits the highest light harvesting efficiency (0.9826), and open‐circuit voltage. A detailed donor–acceptor investigation of QL8/PBDB‐T revealed the marvelous charge switching at the donor–acceptor interface. The approach used in this study is anticipated to facilitate the manufacturing of highly efficient OSC molecules.

Effect of Number and Position of Chlorine Atoms on the Photovoltaic Performance of Asymmetric Nonfullerene Acceptors.

It has been well proved that the introduction of halogen can effectively modify the optoelectronic properties of classic symmetric nonfullerene acceptors (NFAs). However, the relevant studies for asymmetric NFAs are limited, especially the effect of halogen substitution number and position on the photovoltaic performance is not clear. In this work, four asymmetric NFAs with A-D-A1-A2 structure are developed by tuning the number and position of chlorine atoms on the 1,1-dicyanomethylene-3-indanone end groups, namely, A303, A304, A305, and A306. The related NFAs show progressively deeper energy levels and red-shifted absorption spectra as the degree of chlorination increases. The PM6:A306-constructed organic solar cells (OSCs) give a champion power conversion efficiency (PCE) of 13.03%. This is mainly ascribed to the most efficient exciton dissociation and collection, suppressed charge recombination, and optimal morphology. Moreover, by alternating the substitution position, the PM6:A305-based device yielded a higher PCE of 12.53% than that of PM6:A304 (12.05%). This work offers fresh insights into establishing excellent asymmetric NFAs for OSCs.

Unexpected longer T1 lifetime of 6-sulfur guanine than 6-selenium guanine: the solvent effect of hydrogen bonds to brake the triplet decay.

The decay of the T1 state to the ground state is an essential property of photosensitizers because it decides the lifetime of excited states and, thus, the time window for sensitization. The sulfur/selenium substitution of carbonyl groups can red-shift absorption spectra and enhance the triplet yield because of the large spin-orbit coupling, modifying nucleobases to potential photosensitizers for various applications. However, replacing sulfur with selenium will also cause a much shorter T1 lifetime. Experimental studies found that the triplet decay rate of 6-seleno guanine (6SeGua) is 835 times faster than that of 6-thio guanine (6tGua) in aqueous solution. In this work, we reveal the mechanism of the T1 decay difference between 6SeGua and 6tGua by computing the activation energy and spin-orbit coupling for rate calculation. The solvent effect of water is treated with explicit microsolvation and implicit solvent models. We find that the hydrogen bond between the sulfur atom of 6tGua and the water molecule can brake the triplet decay, which is weaker in 6SeGua. This difference is crucial to explain the relatively long T1 lifetime of 6tGua in an aqueous solution. This insight emphasizes the role of solvents in modulating the excited state dynamics and the efficiency of photosensitizers, particularly in aqueous environments.

Effect of heterocyclic and non-heterocyclic units on FDT-based hole transport materials for efficient perovskite solar cells: a DFT study.

The development of a new structure is one of the important approaches for the advancement of efficient hole-transporting materials (HTMs). In this work, novel and efficient HTMs are designed based on the experimentally reported fluorene-dithiophene (FDT) system which shows the effect of four different units phenyl, pyridine, thiane, and oxane in the FDT unit. The structural, optoelectronic, and charge transport properties of the newly developed HTMs are probed using density functional theory (DFT) and time-dependent DFT (TD-DFT) methodologies. The calculated highest occupied molecular orbital (HOMO) energies for all HTMs are higher compared to the valence band energy level of the perovskite which exhibits outstanding hole extraction ability of all HTMs at the charge buffer interface. In addition, the designed HTMs have red-shifted absorption spectra compared to FDT. The computed hole mobilities of newly designed HTMs are faster compared to that of FDT. Moreover, newly tailored HTMs demonstrate improved solubility. The results indicate that a one thiane and one phenyl unit-based system among all materials is the most suitable for HTM design.

Effects of substitution and conjugation on photophysical properties of ESIPT-based fluorophores with the core of 4-aminophthalimide

4-Aminophthalimide is a highly fluorescent signaling unit with excellent photophysical properties and wide application foregrounds. Based on this, a range of theoretical investigations are conducted on the fluorescent probe (E)-5-((2-hydroxybenzylidene) amino) isoindoline-1, 3-dione (HID) with the core of 4-aminophthalimide using density functional theory (DFT) and time-containing density functional theory (TD-DFT) methods in this paper. The optimized configurations, vertical excitation and emission energies, electronic characteristics and excited-state intramolecular proton transfer (ESIPT) behaviors of the probe HID are discussed in detail. Furthermore, to enhance the luminescent properties of HID, five novel compounds have been designed based on the structure of HID by introducing amino, methoxy and naphthalene groups (–NH2, –OMe and C10H8). Our work thoroughly explores how the property and position of substituents and conjugation affect photophysical characteristics and ESIPT processes. We find that the ESIPT dynamics can be modulated by the substitution and conjugation effects. Specifically, the introduction of amino and methoxy groups at the ortho-position and the introduction of the naphthalene group promote the ESIPT behavior of HID1, whereas the introduction of amino and methoxy groups at the meta-position exhibits the contrary impact. Therefore, we boldly infer that the introduction of electron-donating groups in the ortho-position and the introduction of the conjugated group make the ESIPT process more effortless to occur, whereas the introduction of substituents with opposing natures in the meta-position makes the ESIPT process more difficult to occur. In addition, the ionization potentials (IP), electron affinities (EA) and reorganization energies (λh and λe) of molecules are calculated to assess their potential as luminescent materials. Our work not only reveals the luminescence and ESIPT mechanism of the probe HID1, but also proposes to modulate the ESIPT process through the substitution and conjugation effects. In particular, the designed molecules have better photoelectric properties as a result of their red-shifted absorption and fluorescence spectra, smaller energy gaps, larger transferred charges and greater charge transferred distances, which offers some valuable ideas for the experimental development of more efficient organic luminescent materials with ESIPT properties.

A theoretical study on the role of the π-spacer in the thoughtful design of good light-absorbing dyes with phenothiazine for efficient dye-sensitized solar cells (DSSCs).

In this work, we designed ten new organic phenothiazine dyes bridged by different πi-spacers (PTZ1-PTZ10) of D-π-A type based on the synthesized dye CC202-III for their efficacy in dye-sensitized solar cells (DSSC) applications. To learn how various π-spacers affect their performance in DSSCs, these isolated dyes and dye-cluster systems have had their geometries, electronic structures, absorption spectra, dipole moments, and molecular electrostatic potential examined and talked about. Additionally, a number of quantization parameters that affect power conversion efficiency (PCE), including light collection efficiency (LHE), reorganization energy (λtotal), vertical dipole moment (μnormal), strength electron injection driving force (ΔGinject), regeneration driving force (ΔGreg), excited state lifetime (τ), and open circuit voltage (VOC), were calculated in order to identify the organic dyes that would be best suited for DSSC applications. Calculated results revealed that the designed dyes PTZ3, PTZ4, PTZ5, and PTZ10 exhibit a lower energy gap among all dyes compared to the corresponding CC202-III. Additionally, PTZ3, PTZ4, PTZ5, PTZ7, PTZ8, PTZ9, and PTZ10 exhibit significant red-shifted absorption spectra compared to the other dyes with a larger oscillator strength, which improves the photocurrent density of the devices. The findings thus imply that bridge modification is a workable tactic to raise DSSC effectiveness. We used density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to study the electronic and photovoltaic properties of the dyes designed (PTZ1-PTZ10) to assess their effectiveness in DSSCs. DFT and TD-DFT simulations are theoretically used to deeply analyze key characteristics of all organic dyes that affect open-circuit voltage (VOC) and short-circuit current (JSC) to identify structure-property relationships.

High-Efficiency Binary and Ternary Organic Solar Cells Based on Novel Nonfused-Ring Electron Acceptors.

In this study, three nonfused-ring electron acceptors (2TT, 2TT-C6-F, and 2TT-C11-F) with the same steric hindrance groups (2,4,6-tripropylbenzene) are designed and synthesized and the impact of electron-withdrawing and lateral alkyl side chains on the performance of binary and ternary organic solar cells (OSCs) is explored. For the binary OSCs, 2TT-C11-F with IC-2F terminal groups and lateral undecyl side chains display a red shifted absorption spectrum and suitable energy levels, and the corresponding blend film exhibits appropriate phase separation and crystallinity. Thus, binary OSCs based on 2TT-C11-F achieve an impressive power conversion efficiency of 13.03%, much higher than the efficiencies of those based on 2TT (9.68%) and 2TT-C6-F (12.11%). In the ternary OSCs, 2TT with CC terminal groups and lateral hexyl side chains exhibit complementary absorption and cascade energy levels with a host binary system (D18:BTP-eC9-4F). Hence, the ternary OSCs based on 2TT achieve a remarkable efficiency of 19.39%, ranking among the highest reported values. The research yields comprehensive 2TT-series nonfused-ring electron acceptors, demonstrating their great potential for the fabrication of high-performance binary and ternary OSCs.

Synthesis and Bioluminescence of 'V'-Shaped Firefly Luciferin Analogues Based on A Novel Benzobisthiazole Core.

The design of π-extended conjugation 'V'-shaped red shifted bioluminescent D-luciferin analogues based on a novel benzobisthiazole core is described. The divergent synthetic route allowed access to a range of amine donor substituents through an SN Ar reaction. In spectroscopic studies, the 'V'-shaped luciferins exhibited narrower optical band gaps, more red-shifted absorption and emission spectra than D-luciferin. Their bioluminescence characteristics were recorded against four different luciferases (PpyLuc, FlucRed, CBR2 and PLR3). With native luciferase PpyLuc, the 'V'-shaped luciferins demonstrated more red-shifted emissions than D-luciferin (λbl =561 nm) by 60 to 80 nm. In addition, the benzobisthiazole luciferins showed a wide range of bioluminescence spectra from the visible light region (λbl =500 nm) to the nIR window (>650 nm). The computational results validate the design concept which can be used as a guide for further novel D-luciferin analogues based upon other 'V'-shaped heterocyclic cores.

High-performance fluorinated D-A-D type electrochromic polymers with different structural types of thiophene donor units

In this work, two fluorinated D-π-A-π-D type electrochromic polymer precursors were synthesized by Stille coupling reactions that using mono-fluorine atom substituted benzothiadiazole (F-BT) as acceptor units (A), 3-dodecylthiophene as the π-bridge, and thiophene (Th) and 3,4-ethoxylenedioxythiophene (EDOT) as donor units (D), respectively, and their optical properties were characterized by various analytical techniques. All of them were electropolymerized into the corresponding fluorinated electrochromic polymer films (P(F-Th) and P(F-EDOT)). F-EDOT has red-shifted absorption spectra and emission spectra but with relatively lower fluorescence quantum yield, which is due to the strong electron donating ability of EDTO unit. The lower oxidation potential of F-EDOT (0.72 V) is very beneficial to improve the optoelectronic properties of its electropolymerized P(F-EDOT) with favorable redox activity and better redox stability (remained 73 % redox activity after 1000 cycles). Due to the enhanced π-π* conjugation effect, P(F-EDOT) has shown a red-shifted absorption spectra compared to P(F-Th) and a decreased optical band gap (1.6 eV for P(F-Th); 1.38 eV for P(F-EDOT)). Although P(F-Th) has a higher coloration efficiency (370.4 cm2C−1 at 894 nm) and faster response time (0.04–0.37 s), the transparent green P(F-EDOT) should have more satisfied electrochromic properties due to its favorable coloration efficiency (192 cm2C−1 at 458 nm), higher optical contrast (20.6 % at 458 nm), and also very fast response time (0.2–0.86 s), especially the enhanced optical stability and better memory effect. Overall, these properties highlight the potential applications of the current fluorinated D-π-A-π-D type polymers in displays and smart windows.

Synthesis and photocatalytic properties of silicon-doped TiO2 nanotubes

In this study, we present the synthesis and photocatalytic properties of Silicon (Si)-doped TiO2 nanotubes (TNTs) using the hydrothermal method. The doping level of Silicon, expressed as the dopant (Si/(Si + Ti)) molar ratio, was varied within the range of 1–30 %. X-ray diffraction analysis confirmed the presence of the nanocrystalline anatase phase in both pristine and Silicon-doped TNTs. Significantly, we observed an interesting enhancement in the crystallinity and purity of the anatase phase upon incorporating Silicon into TNTs, a finding that has not been previously reported. The light absorption spectra of the doped TNTs exhibited a Red Shift, with absorption edges shifting from 375 nm to 410 nm compared to undoped TNTs. The photodegradation experiments demonstrated the favorable photocatalytic activity of the Silicon-doped TNTs with a fast response to stimulus light. The red-shifted absorption spectra, coupled with the enhanced crystallinity of the anatase phase, contributed to improved performance in the degradation of target compounds.

Photovoltaic response promoted via intramolecular charge transfer in pyrazoline-based small molecular acceptors: Efficient organic solar cells

Herein, a series of pyrazoline based non-fullerene compounds (THP1-THP8) having ladder-like backbone was designed by structural modulation with various electron accepting moieties. The density functional theory (DFT) and time-dependent functional theory (TD-DFT) study was executed at M06/6-311G(d,p) level for structural optimization and to determine the electronic and optical characteristics of the pyrazoline based chromophores. The optimized structures were employed to execute frontier molecular orbital (FMO), transition density matrix (TDM), density of state (DOS), open circuit voltage (Voc) and reorganization energy analyses at the aforementioned level of DFT to comprehend the photovoltaic (PV) response of THP1-THP8. The red-shifted absorption spectrum (512.861–584.555 nm) with reduced band gap (2.507–2.881 eV) allow considerable charge transferal from HOMO to LUMO in all the studied compounds. Global reactivity parameters (GRPs) demonstrated high softness with considerable reactivity in THP1-THP8. Moreover, remarkable Voc values (2.083–2.973 V) were noted for all the derivatives (THP1-THP8). However, THP2 with lowest energy gap (2.364 eV), highest λmax (617.482 nm) and softness (0.423 eV) values is considered good candidate among afore-said chromophores. Hence, the studied chromophores with efficient properties are appropriate for experimentalists in terms of manufacturing of efficient OSCs.

Raman Characterization of Guanine Functionalized SWCNTs

Single-walled carbon nanotubes (SWCNTs) have unique photophysical properties that render them an important class of materials for future nanoelectronics and bio-nano sensor applications. A method was recently discovered for making spatially patterned modifications to SWCNT band gaps and thereby modulating their electronic and optical properties in a controlled manner. The reaction used for this is called guanine functionalization.1 It is achieved by generating singlet oxygen in a dispersion of SWCNTs coated with single-stranded DNA, resulting in covalent bond formation between the guanine nucleobases in the DNA coatings and the nanotube sidewalls. Each of the many covalently bonded guanine sites acts as a weak exciton trap, causing red-shifted SWCNT emission and absorption spectra. Fluorescence spectroscopy shows that the extent of guanine functionalization can depend strongly on SWCNT structure, but spectral broadening can hamper the precise deconvolution of emission features of different (n,m) species. To track such covalent functionalization through Raman scattering, the D to G band ratios are commonly used as a measure of sp3 defect density and therefore of the functionalization extent. However, this conventional Raman method cannot show which (n,m) species in unsorted samples have been functionalized, because they all contribute to the D and G band signals. We will describe a novel Raman analysis based on the relative intensities of bands that have shifts located between the RBM and D regions. These Raman features are found to be diameter-specific, allowing estimation of (n,m)-resolved functionalization extents in unsorted SWCNT samples. In addition, we will present an assignment and interpretation of the relevant Raman features. Zheng, Y.; Bachilo, S. M.; Weisman, R. B., Controlled patterning of carbon nanotube energy levels by covalent DNA functionalization. ACS Nano 2019, 13, 8222-8228.

First Principles Study of the Photoelectric Properties of Alkaline Earth Metal (Be/Mg/Ca/Sr/Ba)-Doped Monolayers of MoS2.

The energy band structure, density of states, and optical properties of monolayers of MoS2 doped with alkaline earth metals (Be/Mg/Ca/Sr/Ba) are systematically studied based on first principles. The results indicate that all the doped systems have a great potential to be formed and structurally stable. In comparison to monolayer MoS2, doping alkaline earth metals results in lattice distortions in the doped system. Therefore, the recombination of photogenerated hole-electron pairs is suppressed effectively. Simultaneously, the introduction of dopants reduces the band gap of the systems while creating impurity levels. Hence, the likelihood of electron transfer from the valence to the conduction band is enhanced, which means a reduction in the energy required for such a transfer. Moreover, doping monolayer MoS2 with alkaline earth metals increases the static dielectric constant and enhances its polarizability. Notably, the Sr-MoS2 system exhibits the highest value of static permittivity, demonstrating the strongest polarization capability. The doped systems exhibit a red-shifted absorption spectrum in the low-energy region. Consequently, the Be/Mg/Ca-MoS2 systems demonstrate superior visible absorption properties and a favorable band gap, indicating their potential as photo-catalysts for water splitting.

First‐Principles Study of the Effects of La2+/3+ Doping and Oxygen Vacancies on TiO2 Magnetism, Carrier Lifetime, Activity, and Absorption Spectra

The effects of photocatalytic performance and magnetism between La doping and oxygen vacancy on rutile and anatase TiO2 systems are rarely compared. Oxygen vacancies in rutile and anatase TiO2 are also experimentally challenging to control accurately. Herein, the first‐principles generalized gradient approximation (GGA + U) method is used to investigate the effects of La2+/La3+doping and oxygen vacancy on TiO2 magnetism and photocatalytic performance. Results of magnetic calculation show that La2+ doping and oxygen vacancies are magnetic to TiO2, whether rutile or anatase, and that the bound magnetic polaron is the source of ferromagnetism in the anatase Ti15La2+O31 system. The anatase Ti30La22+O62 system can achieve room‐temperature ferromagnetism at Curie temperature. The calculation results of photocatalytic performance show that the anatase‐type Ti15La3+O31 system has minimum formation energy, the highest stability, maximum electric dipole moment, the strongest carrier activity, the strongest polarization ability, the slowest electron–hole recombination, the longest lifetime, and remarkable absorption spectrum redshift among the tested systems.

Elucidating modelling of C≡N-based carbazole-arylamine hole transporting materials for efficient organic and perovskite solar cells

Recently, the scientific community has shown great interest in hole transport materials (HTMs) to develop efficient and stable organic and perovskite solar cells. To boost the photovoltaic performance of these solar cell devices, scientists have been investigating the use of modified HTMs. In this study, we have developed a distinctive and proficient approach to building a better photovoltaic material by modifying the endcaps of the reference (MA). Specifically, we designed five new efficient HTMs (MA1-MA5) through molecular engineering on a terminal of reference molecule MA. Using density functional theory (DFT) and time-dependent-DFT methods, we theoretically characterized the key characteristics of these newly designed materials, including the orientation of frontier molecular orbitals (FMO), absorption maxima, the partial density of states (PDOS), binding energies, reorganization energy, transition density matrix, fill factor (FF), open-circuit voltages (Voc) and power conversion efficiencies (PCEs) for these materials. Our theoretical representations revealed that newly constructed materials (MA1-MA5) have a highly red-shifted absorption spectrum with lower binding energies and narrow energy gaps, making them ideal for charge shifting. Among these designed MA1-MA5 materials, the MA1 has the potential to produce as much as higher 23.24% PCE when it will be used in fabricating solar cell devices, whereas, the other designed materials MA2-MA4 has also very comparable and much higher PCE values than the refence molecule MA. These findings demonstrate our efficient designing approach to tune the photovoltaic and optoelectronic properties of the HTMs, and we recommend these engineered materials for the future developments of an efficient solar cell devices.