The course for improving the stability and electronic transport properties of electrode materials is crucial for obtaining high-performance organic solar cells and warrants attention. The current study explores the potential of graphite as an anode-based counter electrode material for organic solar cell applications using a first-principles calculations approach. The study focuses on the effect of chitosan molecules on the charge transfers and optical response properties of graphite. The adsorption of chitosan onto graphite showed a negligible lattice mismatch and decreased cohesive energies, suggesting improved stability. The increased density of states of graphite with chitosan incorporation suggests the presence of delocalized electronic states near the Fermi level. The optical response properties show increased absorption with chitosan adsorption on graphite surface, suggesting the introduction of surface dipoles and light absorption. The variation of the refractive index of graphite ( 1.23 → 1.45 ) with chitosan adsorption suggests significant interfacial charge transfers. The bulk of the charge transfer behaviour can be attributed to the π-π and n-π transitions. Hence, chitosan-supported graphite heterostructures can act as potential anode electrode materials for organic solar cells and other optoelectronic applications. All computations were performed using density functional theory (DFT) as implemented in the CASTEP code, the DMol package, and the adsorption locator tool. The geometric structures were optimized using the generalized gradient approximation (GGA) with the Perdew–Burke–Ernzerhof (PBE) exchange-correlation functional. The electronic and optical properties were studied using the same norm-conserving pseudopotentials of the CASTEP code.

Solar energy harvesting and conversion has attracted a lot of scientific interest because solar energy is believed to be clean and sustainable. In this study, we report the synthesis of porous TiO 2 by sol-gel method and later doped with Thulium rare earth ions (Tm 3+ ) for potential application in organic solar cells as electron transport layers (ETL). Additionally, density functional theory (DFT) calculation was performed with CASTEP computational suite to explore further the optoelectronic and charge transfer mechanisms in the Tm(III)-doped TiO 2 nanomaterials. Thereafter, the experimental material’s band gap values were extracted and used in the numerical simulation of the designed organic solar cell with a general configuration of FTO/TiO 2 /PBDB-T/ITIC/Cu 2 O/Ag, via SCAPS-1D numerical simulator. The experimental results showed a steady reduction in the band gap of TiO 2 with increased Tm 3+ doping. The electrical conductivity properties showed an enhanced feature when TiO 2 was doped with Tm 3+ nanoparticles. The calculated band gap from the density functional theory study shows a similar decreasing band gap trend with that of the experimental data, suggesting the transport properties from DFT are sufficient to describe the experimental data. The electronic transfer behaviour is analogous to metal-metal and metal-oxides transport features, which can be attributed to Ti – Tm and Tm – O – Ti hybridizations, as indicated in the orbital state alignment. The best performing modelled device with Tm(III)-doped TiO 2 (1.0 mol%) as ETL attained a PCE of 21.83%, V oc of 1.54 V, J sc of 31.87 mA cm − 2 and FF of 44.44% which was attributed to better charge transfer characteristics and effective band alignment between the ETL and absorber, thus, better efficiency. The study proposes that Tm(III)-doped TiO 2 can act as a suitable n-type material that can propel the realisation of high-performance OSCs for commercialization in the future.

The magnetic field contribution to charge transfers of active layer materials for organic solar cells has been topical recently. The current study focuses on the effect of rare earth Tm doping on the charge transfer and magneto-optical properties of TiO2. The Tm doping effect on TiO2 shows a transition from ferromagnetic-antiferromagnetic-ferrimagnetic features. A steady band gap narrowing is observed with Tm doping of TiO2, which suggests increased localized defect buildup within the electronic structure of TiO2. The transition from electropositive to electronegative charge transfer features suggests Tm doping can act as a means of tuning the optoelectronic properties of TiO2. Additionally, the asymmetric spin-up and down features of Tm 4f orbital states suggest it is an active agent in tuning the magneto-optical properties of TiO2 for improved organic solar cell harvesting.

The use of molecular complexes in improving the transport properties of active layer materials for organic solar cells has been enormous in the recent era. The current study focuses on the transport and optical properties of dithiocarbonate-based complexes on Tin sulphide/Cobalt sulphide heterostructure. The charge transfer properties show electronegativity features for the N-butylamine complex, whereas electropositive transport features are observed for the N-dodecyl amine and mixed (N-butylamine/N-dodecylamine) complex blend. This charge transfer behaviour is consistent with typical acceptor-donor features, which are associated with metal-thiocarbamate complex transport. The optical features for dithiocarbonate-based complexes supported metal sulphide heterostructure show increased absorption and reflective plasmonic features in comparison with pristine metal sulphide heterostructure. The study proposes the incorporation of a dithiocarbonate complex as support for metal sulphide heterostructure active layer material that can be used to drive improved charge transport and localized surface plasmon resonance, which is crucial for charge transport in organic solar cell devices.

Porous titanium dioxide (TiO2) was synthesized by incorporating polyvinylpyrrolidone (PVP) polymer. However, its application is limited due to its poor absorption of visible light. In this study, trivalent lanthanide metals (Ho3+ and Er3+) were added to sol-gel-produced crystalline tetragonal rutile phase TiO2 to enhance light absorption and photocatalytic degradation efficiency. X-ray diffraction (XRD) analysis revealed that the crystallite size decreased with doping. Additionally, doping was found to increase the absorption bands and reduce photoluminescence (PL) quenching. The resulting porous photo-and electroactive materials were capable of degrading methylene blue dye in an aqueous solution through photocatalysis after sufficiently absorbing UV light. Er-doped TiO2 (Er-TiO2) exhibited superior performance in photocatalytic degradation efficiency (PCDE) compared to Ho-doped TiO2 (Ho-TiO2) and undoped TiO2, attributed to its enhanced light absorption, porous structure, and lower electrochemical impedance solution resistance (EIS). The resistance values were as follows: 30.1 S2 for Er-TiO2, 49.6 S2 for Ho-TiO2, and 59.2 S2 for TiO2. Density functional theory (DFT) calculations indicated that electronegative charge transfers were responsible for the photodegradation mechanism observed in the experimental data.

The use of metal sulfides for organic photovoltaics has been a widely studied topic in recent years. The current study reports on the impact of aniline and piperidine ligands on the transport and optical properties of SnS/CoS heterostructure, using the first principles density functional theory approach. The charge transfer properties possess an electropositive and electronegative feature for both the aniline and piperidine ligands, respectively. This charge transfer behaviour is consistent with metal-to-ligand charge transfer properties. The optical properties of SnS/ligand/CoS retain its optical plasmonic transitions for both ligand types, with a corresponding damping effect in the absorption, which suggests interfacial charge transfer-type interactions. Also, an increased density of states for both ligand types is observed, implying increased availability of unoccupied states for electronic transport. These results of ligand-incorporated SnS/CoS suggest its potential for future improved charge transfers in organic solar cells.

Titanium trisulfide monolayer (TiS3) 3 ) is a quasi-1D crystal with promising applications in a range of fields, including photoelectrochemical cells and thermoelectrics. Despite the emerging importance of monolayer TiS3, 3 , little is known regarding its intrinsic defects. In this work, we systematically investigate the stability, electronic, and magnetic properties of native defects in single layer TiS3, 3 , using Density Functional Theory. We consider S and Ti monovacancies, divacancies, extended Ti-nS n S (n n = 2-8) ) vacancy complexes, S and Ti antisites, as well as their complexes. We show that the likelihood of the formation of sulfur vacancies is strongly dependent on the symmetrically inequivalent lattice site at which the S vacancy is located. Under S-rich conditions, single sulfur vacancies are shown to be energetically more favorable than divacancies. In contrast, under Ti-rich conditions sulfur divacancies are more favorable than single S vacancies. We show that S Ti and TiS S 1 are most likely to form under S-rich and Ti-rich conditions, respectively, with low formation energies of-10.42 eV and-9.18 eV, and are therefore likely to be prevalent in single layer TiS3. 3 . We further consider defect levels in the band-gap, and show that several of these intrinsic defects are potential n-type or p-type dopants, while others will form deep electron/hole traps. Further, we show that while a number of these intrinsic defects induce no spin in the host, most intrinsic defects will induce a net magnetic moment in the host. The commonality of these defects in TiS3, 3 , will significantly impact applications such as spintronics, thermoelectrics, and the manufacturing of electronic devices.

Transition metal-ruthenium alloys are promising candidates for ultra-high-temperature structural applications. However, the mechanical and electronic characteristics of these alloys are not well understood in the literature. This study uses first-principles density functional theory calculations to explore the structural, electronic, mechanical, and phonon properties of X3Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) binary alloys in the tP16 crystallographic phase. We find that Mn3Ru, Sc3Ru, Ti3Ru, V3Ru, and Zn3Ru have negative heats of formation and hence are thermodynamically stable. Mechanical analysis (Cij) indicates that all tP16-X3Ru alloys are mechanically stable except, Fe3Ru and Cr3Ru. Moreover, these compounds exhibit ductility and possess high melting temperatures. Furthermore, phonon dispersion curves indicate that Cr3Ru, Co3Ru, Ni3Ru, and Cu3Ru are dynamically stable, while the electronic density of states reveals all the X3Ru alloys are metallic, with a significant overlap between the valence and conduction bands at the Fermi energy. These findings offer insights into the novel properties of the tP16 X3Ru intermetallic alloys for the exploration of high-temperature structural applications.

In this study, nitrogenated reduced graphene oxide (N-rGO) was synthesized and functionalized with iron III oxide (Fe 2 O 3 ) nanoparticles via a two-step facile sol–gel method. The electrical properties of N-rGO functionalized Fe 2 O 3 nanoparticles showed enhanced electrical conductivity for low Fe 2 O 3 concentration. The I–V characteristics further showed the conversion of p -type to n -type semiconducting features. The enhanced electrical conductivity can be attributed to induced defects arising from the incorporation of Fe 2 O 3 nanoparticles into the N-rGO matrix. Density functional theory calculations showed the formation of unoccupied states below the Fermi level, as well as charge transfer between C, N, Fe, and O atoms. The improved electrical conductivity and conversion of p- to n -type semi-conductivity can be attributed to the hybridization between the C 2p, O 2p, N 2p, and Fe 3d orbitals, and could lead to increased potential of rGO composite for electronic device applications.

Owing to its potential for energy harvesting and storage, layered SnS2 has become increasingly popular in the energy storage and conversion community. The current study proposes a layered stacking configuration of SnS2/ graphene heterostructure, which could improve its stability and electronic transport properties for optoelectronic and solar cell applications. The study utilizes the first-principles Density Functional Theory approach to investigate the electronic and optical properties of bilayer and sandwich-layered SnS2/graphene heterostructures for energy storage applications. The low magnitude of the cohesive energy of SnS2 in both the bi- and sandwich cases (0.3604 -> 0.0057 -> 0.0522eV) of both heterostructures reflect feasible experimental reproducibility. Additionally, a reduction of the band gap (2.338 -> 0.604 -> 0.595 eV) with corresponding charge redistribution is observed, suggesting increased electron conductivity. The calculated density of states in both cases suggests increased formation of unoccupied orbital states, with prominence of the S 3p orbital states, depicting the capability of synergistic interaction with Sn and C atoms.

We use first-principles density functional theory calculations to study the properties of X–Ru alloys (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) in the B2 crystallographic phase for high-temperature structural applications.

Effects of caffeine and titanium dioxide (TiO2) in methylammonium lead iodide (MAPbI3/CH3NH3PbI3) as a photon absorber are studied. XRD showed high crystallinity of TiO2:Caffeine:MAPbI3 with larger crystallite size of -3.9 nm compared to TiO2:MAPbI3 with -3.6 nm. Large grain size of -550 mu m was obtained for TiO2: Caffeine:MAPbI3 compared to -256 mu m of TiO2:MAPbI3. Rod-like structures were observed though TiO2: Caffeine:MAPbI3 morphology and was smoother compared to TiO2:MAPbI3. Reduced bandgap energy of -2.3 eV was observed from TiO2:Caffeine:MAPbI3 and PL quenching indicated the possibility of reduction of the electronhole recombination. TiO2:Caffeine:MAPbI3 showed better electrical conductivity compared to TiO2:MAPbI3. Density functional theory calculations showed increased charge transfer/redistribution which accounts for the slight enhanced electrical conductivity for TiO2:Caffeine:MAPbI3. The density of state calculations suggests the formation of unoccupied states and O 2p, Ti 3p, N 2p and C 2p as major contributors to the electronic and electrical properties of TiO2:Caffeine.

The formation of metal dichalcogenide heterostructures enables tailoring their properties for future optoelectronics and energy storage. The current paper focuses on the study of the effect of interlayer spacing on the electronic and optical properties of SnS2/graphene/SnS2 sandwich heterostructure, using density functional theory electronic structure calculations. We find low cohesive energies/ per atom ( 0.0506 → 0.0514 eV) for all the various interlayer spacing configurations (1–5 Å) considered in this study, implying the feasibility of experimental realization. The Mulliken charge transfer analysis suggests negative to positive net charge ( -0.12 → 0.18 ) transfer for 1–3 Å threshold interlayer spacing, which implies acceptor and donor charge transfer configurations. The density of states of SnS2/graphene/SnS2 retains unoccupied states for all the interlayer spacing configurations, which can be attributed to localized exciton states and strong electronic coupling between the electrons within the heterostructure layers. We further find a strong optical response and localized electronic transport, which can pave the way for optoelectronic applications of this material heterostructure.

In this work, the effect of caffeine concentration (2 %, 4 %, 6 % and 8 %) on crystallinity and thermal stability of MAPbI(3) was successfully studied. MAPbI(3) showed stability at lower temperatures ranges between 0 and 90 degrees C, however, after adding caffeine the thermal stability showed an improvement towards higher temperatures [196-242 degrees C]. All the samples exhibited intense diffraction peaks at similar to 2 theta = 19.66 degrees and 39.81 degrees, respectively assigned to the (112) and (141) planes of tetragonal perovskite structure which indicates that the desired perovskite film was formed. MAPbI(3)@Caffeine (8 %) and MAPbI(3)@Caffeine (6 %) exhibited high PL intensity quenching which indicates their high charge carrier extraction efficacy which can be attributed to the higher crystallinity and fewer defect states of the film compared to MAPbI(3)@Caffeine (2 %) and MAPbI(3)@Caffeine (4 %) samples. MAPbI(3)@Caffeine (8 %) absorption spectra had the shifts to low wavelength in the range 491-532 nm which indicated that caffeine may allow sufficient photon into MAPbI(3) due to the estimated bandgap. The density functional theory calculations suggest increased interactions at high caffeine concentration with corresponding switch from metallic to semiconducting properties. The stability of MAPbI(3) can be attributed to increased cationic interaction between I 5p orbital states and C 2p, N 2p orbital states as indicated in the PDOS and electron density difference analysis.

We present the structural, elastic, electronic, magnetic, and phonon properties of D0c X _3 Ru (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) alloys in their respective ground-states at zero pressure using first-principles density functional theory (DFT). The calculated heat of formation for Sc _3 Ru, Ti _3 Ru, V _3 Ru, Mn _3 Ru, and Zn _3 Ru are negative, signifying their thermodynamic stability. Meanwhile, we find that Sc _3 Ru, V _3 Ru, Mn _3 Ru, Co _3 Ru, Ni _3 Ru, Cu _3 Ru and Zn _3 Ru alloys are mechanically stable. The electronic properties indicate a metallic nature in all the X _3 Ru alloys due to valence-conduction band overlap at the Fermi energy. Additionally, the phonon dispersion curves suggest that Cr _3 Ru, Fe _3 Ru, Ni _3 Ru, Cu _3 Ru, and Zn _3 Ru are dynamically stable. These results provide a comprehensive overview of the stability, electronic, and mechanical properties of D0c Zn _3 Ru structures, suggesting their suitability for engineering novel alloys in high-temperature structural applications.

Titanium trisulfide monolayer (TiS3) is a quasi-1D crystal with promising applications in a range of fields, including photoelectrochemical cells and thermoelectrics. Despite the emerging importance of monolayer TiS3, little is known regarding its intrinsic defects. In this work, we systematically investigate the stability, electronic, and magnetic properties of native defects in single layer TiS3, using Density Functional Theory. We consider S and Ti monovacancies, divacancies, extended Ti-nS (n=2−8) vacancy complexes, S and Ti antisites, as well as their complexes. We show that the likelihood of the formation of sulfur vacancies is strongly dependent on the symmetrically inequivalent lattice site at which the S vacancy is located. Under S-rich conditions, single sulfur vacancies are shown to be energetically more favorable than divacancies. In contrast, under Ti-rich conditions sulfur divacancies are more favorable than single S vacancies. We show that STi and TiS 1 are most likely to form under S-rich and Ti-rich conditions, respectively, with low formation energies of -10.42 eV and -9.18 eV, and are therefore likely to be prevalent in single layer TiS3. We further consider defect levels in the band-gap, and show that several of these intrinsic defects are potential n-type or p-type dopants, while others will form deep electron/hole traps. Further, we show that while a number of these intrinsic defects induce no spin in the host, most intrinsic defects will induce a net magnetic moment in the host. The commonality of these defects in TiS3, will significantly impact applications such as spintronics, thermoelectrics, and the manufacturing of electronic devices.

Using the density-functional theory approach, including Hubbard U correction, we investigate the defect structures consisting of vanadium (V) atoms embedded in a monolayer silicene. Specifically, we consider V–V atom pairs in antiferromagnetic (AFM), ferromagnetic (FM), and non-magnetic states, which are embedded in substitutional and interstitial sites. We determine the ground-state structures, formation and binding energies, electronic structures, induced magnetization, as well as the spin-exchange coupling between the V–V pair. For the substitutional vanadium atom pair, the stability of the AFM and FM spin configurations depends on the sublattice sites in which the V atoms are sited. When the V pair is located on a similar sublattice site type, the AFM spin alignment is more energetically favored, whereas when the pair is located in a different sublattice site, the FM interactions are more stable. However, the relative stability of the AFM or FM configurations changes rapidly as the separation between the V pair increases. Regarding the interstitial-hole V–V pair configurations, the most stable structure is when the pair is at the nearest-neighbor hole sites and is in an FM alignment. Also, at larger separations, the AFM or FM hole configurations are approximately degenerate in energy. Furthermore, we elucidate on the Ruderman–Kittel–Kasuya–Yosida, direct-exchange, and the superexchange interaction mechanisms in the vanadium-embedded silicene. In addition, we estimate a Curie temperature (Tc) of up to ∼500 K for a silicene structure containing a V pair in the FM spin alignment. Such a high Tc, in addition to the stability of the material, suggests that vanadium-embedded silicene is a potential candidate material for spintronic device applications.

The current study focuses on the superparamagnetic properties of reduced graphene oxide achieved through varying the crystallite size of rGO nanosheet and incorporating gold nanoparticles (Au-NP). Superparamagnetic features were observed for rGO and Au-NP functionalized rGO (rGO: Au-NP) with corresponding low remanence and coercivity. The superparamagnetic features can be attributed to the crystallite sizes of rGO and rGO: Au-NP as evidenced from X-ray diffraction crystallite size analysis. Density functional theory calculations showed the formation of additional unoccupied states with a corresponding increase in spin density contributions from the hydroxyl functional group and Au atomic doping. The partial density of states revealed C-2p, O-2p, and Au-5d orbitals as the major contributors to the magnetic properties of rGO composites.

In this report, a GO:Fe2O3 nanocomposite was synthesized using a one-step covalent attachment approach using a sol-gel technique. The optical absorbance, photoconductive, photo-capacitive, and electrical properties were obtained using spectroscopy, and current-voltage (I-V) measurements. An enhanced optical absorbance with corresponding band gap reduction is observed when Fe2O3 nanoparticles are incorporated in GO. A corresponding enhanced photoconductance in the order of ×101 was observed due to the impact of band gap narrowing. The enhanced photoconductivity and photo-capacitance can be attributed to energy and charge transfer between GO and Fe atoms, leading to the generation of photo-induced excitons. Density function theory calculations indicate increased charge transfer when GO is doped with Fe-O atoms, which is consistent with experimental data. The observed results could potentially enable the use of GO:Fe2O3 nanocomposites for photodetectors and other optoelectronic applications.

In this report, we studied the impact of particle size-lattice strain on the magnetic properties of reduced graphene oxide functionalized with iron oxide (rGO: Fe3O4) nanocomposite. The microstrain analysis from X ray diffraction data analysis showed increased microstrain at low atomic concentration of Fe3O4 in rGO. While the effect of rGO functionalization with Fe3O4 leads to overall enhancement of the magnetization (rGO: $$17 \times {10}^{-6}\to$$ rGO: Fe3O4 (I): $$24 \times {10}^{-2}\to$$ rGO: Fe3O4 (II): $$5.5 \times {10}^{-2}$$ emu/g), the microstrain also plays a crucial role. The microstrain-based magnetic enhancement can be attributed to increased defects emanating from Fe atoms. Density function theory calculations showed increased density of state above the Fermi energy, suggesting formation of unoccupied states, which explains the enhanced magnetization. The partial density of state showed C 2p, O 2p and Fe 3d orbital states as the major contributors of the observed magnetic properties.