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Outstanding material properties allowed perovskite solar cells’ power conversion efficiencies (PCEs) exceed 25% within a decade, demonstrating the most rapid increase rate in PCEs among all the existing photovoltaic (PV) technologies. Despite such significant progress perovskite technology commercialization requires further enhancement in device performance. Here, we report a strategy for optimizing interfacial quality of the perovskite solar cells (PSCs). The interfacial layer between the electron transport layer (ETL) and the perovskite absorber were optimized by interface engineering technique via preparing the ETL consisted of Tin(IV) oxide (SnO2) quantum dots (QDs), SnO2 nanoparticle (NP) and a passivation layer based on Poly(methyl methacrylate): [6,6]-phenyl-C61-butyric acid methyl ester (PMMA:PCBM). It was demonstrated that the PSCs with a single-layer ETL made of SnO2 QDs exhibit strong I-V hysteresis, while the application of a triple-layer ETL effectively suppresses the hysteresis due to the optimization of ETL/perovskite interface. This work demonstrated the effective protocol which can substantially improve the performance of PSCs and eliminate the I-V hysteresis.

Here, we report on the progress of our work on fabrication of simple metal–semiconductor-metal perovskite solar cells, in which the metal electrodes directly contact the perovskite layer to create Schottky junction solar cells. The photovoltaic properties of the device strongly depend on the asymmetry in work function values of two metal contacts, which are gold back-contact electrode and silver nanowires percolation network. Modified polyol synthesis was used to produce silver nanowires. To achieve homogeneous, uniform and highly-conductive network formed by silver nanowires on the perovskite layer, various fabrication protocols (deposition technique, ambience, solvent, volume, etc.) have been tested. We have developed several protocols for obtaining silver nanowires network-based electrodes deposited on top of thin perovskite films on glass substrates with the sheet resistances of the silver nanowires network as small as ∼ 2 KΩ/□.

Binary CuxCoySz sulfide based Pt-free counter electrodes (CE) were prepared in one-step solvothermal synthesis process. The obtained CEs were characterized by SEM, XRD, and Raman spectroscopy methods. EDX analysis showed uniform distribution of Cu, Co and S. SEM images revealed different level of coverage of the FTO glass by the binary metal sulfide products. DSSCs were constructed using proposed CEs with N719 dye, and their photovoltaic and electrochemical performances were assessed against Pt reference cell. The efficiency of the CuxCoySz-3 CE produced an 11% improvement of its photovoltaic efficiency compared to the reference cell.

Porphyrin dyes are susceptible to aggregation which may cause lower short-circuit current density affecting its photoelectric conversion efficiency (PCE) in dye-sensitized solar cells. In this paper, we harness the inherent property of metallated porphyrins that it can axially coordinate with compounds containing lone-pair of electrons, such as pyridines, through the back π-bonding. The use of pyridine or bipyridine spacers to suppress aggregation in β -functionalized Zn-tetraphenylporphyrin-based dyes showed improvement of PCEs by 28% and 44% for 4-methylpyridine and 4,4′-bipyridine ligands, respectively. This clearly demonstrates the benefits of the simple but effective method in suppressing dye aggregation thereby increasing its efficiency.

There is an increasing need for the development of probes for the detection of hexavalent chromium since it is a known carcinogen, which can cause adverse effects on human health. Metal-organic frameworks (MOFs) have shown successful detection and removal of hazardous substances from aqueous media. This work presents the use of simple organic ligands such as 3-pyridinecarboxaldehyde and trimesic acid with Zn(II) ion to fabricate a new MOF that exhibits sensitive and selective luminescence quenching response towards CrO4 2− and Cr2O7 2− species in aqueous solution. The MOF showed a detection limit of 0.67 μM (0.078 ppm) as CrO4 2− species and 1.91 μM (0.41 ppm) as Cr2O7 2− species. Results reveal that the as-synthesized MOF could serve as a good luminescent sensor for CrO4 2− and Cr2O7 2− species in the contaminated aqueous phase.

A series of iminophosphinite POCN pincer Ni(ii) complexes, (POCN)NiMe and (POCN)NiLn(BX4) (L = CH3CN, n = 0, 1; X = F, Ph, C6F5), have been developed and subjected to catalytic hydrosilylation of alkenes, aldehydes and ketones and hydroboration of carbonyl compounds. The stoichiometric reactivity of (POCN)NiMe and (POCN)Ni(BF4) with PhSiH3 and HBPin suggests that catalytic reactions proceed via the hydride intermediate (POCN)NiH. With regard to reactions with HBPin, efficient and mild hydroboration of a variety of carbonyl compounds, including highly chemoselective hydroboration of benzaldehyde in the presence of other common potent reductive functional groups, such as alkenes, alkynes, esters, amides, nitriles, nitro compounds and even ketones, and the first example of base metal catalyzed hydroboration of amides, including mild direct hydroborative reduction of primary and secondary amides to borylated amines were demonstrated for (POCN)NiMe.

This work reports the impact of electron transport layers (ETLs) on the performance of perovskite solar cells (PSCs). The ETLs are based on tin (IV) oxide (SnO 2 ) prepared in different nanostructures. The carrier transport properties of PSCs are systematically characterized and the underlying mechanism for the enhancement in performance of PSCs is found. The strategies for optimizing the interface between the ETL and perovskite are demonstrated, yielding a champion device with a power conversion efficiency (PCE) of 20.8 %.

This paper reports new D-D-π-A dyes based on N-annulated perylene, emphasizing the enhanced dye-to-semiconductor charge-transfer mechanism. A series of DFT calculations for new tPA-perylene-based dyes was conducted, starting from the systematic selection of DFT methods by reproducing the experimentally obtained properties of known perylene-based sensitizers. Accordingly, using the LC-ωPBE xc functional with 6-31+G(d) basis set for the time-dependent calculations of the excitation energies, a damping parameter of ω = 0.150 Bohr–1 was found to be most appropriate for dyes having spatial orbital overlap value of 0.21 ≤ ΛHL ≤ 0.38, while ω = 0.175 Bohr–1 is suitable for analogues with 0.43 ≤ ΛHL ≤ 0.57. Moreover, the mPWHandHPW91/6-31G(d) method gave high accuracy in GSOP calculations. The comparison between the properties of tPA-based donor groups has revealed that the semirigid tPA-based D4 unit is an effective donor group for perylene-based dye. Initial screening of the acceptor designs resulted in PLz4 dy...

Bacteriochlorin-based dyes, having a push-pull type of configuration similar to that of the YD2 dye, were theoretically designed based on modification of the macrocycle and π-conjugated bridge for use in dye-sensitized solar cells. Various parameters were assessed to determine its structure-property relationships, such as the absorption profile based on time-dependent density functional theory, nonlinear optical properties from (hyper)polarizability data, ground- and excited-state oxidation potentials, and the electronic properties of the free and adsorbed dyes. On the basis of the results, the most appropriate macrocycle would be 7,7,17,17-tetramethyl-7H,8H,17H,18H-porphyrin and, for its π-conjugated bridge, either thieno[3,2-b]thiophene, dithieno[3,2-b:2',3'-d]thiophene, or 4,4-diisopropyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene. These newly designed dyes produced an absorption spectra having a range of 300-800 nm, which could likely increase the light harvesting efficiency. It has better nonlinear properties than the reference, thereby ensuring higher charge-transfer properties. Also, the dye regeneration efficiency is within the optimized value of 0.2 eV, which could minimize the excessive loss of voltage. This shows that through theoretical approach we can deductively design analogues before synthesis to streamline the process in the design of dyes to produce efficient dye-sensitized solar cells.

Water-soluble fluorescent carbon dots (C-dots) were synthesized through hydrothermal process using date pits pre-treated with phosphoric acid as a carbon source. Transmission electron microscopy showed that the C-dots have an average particle size of 1.1 ± 0.3 nm with a very narrow size distribution. The aqueous solution or the phosphate buffer solution (PBS) of as prepared C-dots exhibits strong fluorescence when excited at 338 nm. The PBS solution of the as prepared C-dots can inhibit growth by as much as 61% as well as migration of human lung cancer (A549), breast cancer (MCF-7) and prostate cancer (PC3) cells at the concentration of 0.1 mg/ml. However, only 14% inhibition was observed for kidney (HEK293) cells at the same dose. In addition, the application of C-dots was found to lead to the increase in thickness of the actin stress fiber, which may inhibit cell migration dynamics. Thus, nanomaterials such as date pits-derived C-dots may be applied as anti-cancer agents.

Experimental and theoretical HOMO energy correlation of tetraphenylbenzidine (TPB)-based hole transport materials (HTMs) was successfully achieved through adiabatic ground-state oxidation potential calculation using LC-ωPBE. Similarly, trends in the computed excitation energies and hole reorganization energies of the HTMs are in agreement with the experimental band gaps and hole mobilities, respectively. Using these established correlations, the calculated properties of novel TPB-based HTMs were analyzed, and among the derivatives, TPB with attached fluorene (Fl) has less absorption in the visible region, a lower hole reorganization energy, and a deeper HOMO level compared to the reference. These properties signify that Fl could be a promising HTM in perovskite solar cells because this material will not compete with the perovskite absorption, will be efficient for hole transport due to its better hole mobility, and will eventually enhance the open-circuit voltage of the device. All of these factors could improve the efficiency of the perovskite solar cell.

Two spiro-like organic dyes linked at the thiophene bridge (KS-11 and KS-12) together with the original rod-shaped D-π-A configuration (C1) were designed, synthesized, and characterized based on their electronic structure, and determine the photophysical and photovoltaic properties for its application in dye-sensitized solar cells. Compared to C1, the double D-π-A spiro-like configuration, which consists of two separated light-harvesting moieties, was found to be beneficial to photocurrent generation provided that they are separated properly to prevent intramolecular exciton annihilation. This was observed when KS-11, which is linked at the β-position of the thiophene moiety of D-π-A, was compared with KS-12, where the two D-π-A are linked with an additional thiophene using a α-β linkage. The results show that KS-12 produced a 20% and 17% increase in photovoltaic efficiency under simulated AM 1.5G solar irradiation compared to KS-11 and C1, respectively. This increase in photovoltaic performance is credited mostly to the reduction of recombination effects and the increase in the density of states at the semiconductor surface due to high dye loading and better charge-transfer properties.

This work demonstrates the effectiveness of interfacial engineering and defect passivation in the bulk of mixed perovskite absorber to achieve high performance perovskite solar cells (PSCs). It is found that the extent of I–V hysteresis is most significant in PSCs with a single-layer electron transport layer (ETL) composed of SnO2 quantum dots (QD-SnO2) or SnO2 nanoparticles (NP–SnO2). The hysteresis of the PSCs can be effectively suppressed by adopting a multilayer structure for the ETL to optimize the ETL/perovskite interface. Furthermore, the performance of the PSCs can be enhanced by incorporating a controlled amount of an organic cross linker, 2,2′-(ethylenedioxy)bis (ethylammonium iodide) (EDAI), in the mixed perovskite absorber layers. The experimental results consistently show that incorporation of an optimal amount of EDAI is effective in passivating defect states in the bulk of mixed perovskite as well as the grain boundaries and film surface, while excessive EDAI significantly degrades the photovoltaic (PV) performance of PSCs due to generation of defects and electrically insulating properties of EDAI itself. Owing to the synergistic effect contributed from optimized ETL/perovskite interface and the mixed perovskite thin film, the PSC with an active area of 0.06 cm2 exhibits a champion power conversion efficiency (PCE) of ~19.0% with negligible hysteresis and improved stability. The proposed strategies were also applied to fabricate larger area devices from 0.15 cm2 to 0.85 cm2, exhibiting the PCEs of ~12%–18% with negligible hysteresis.

Indium-doped TiO2 photoanode for dye-sensitized solar cells are prepared using a simple surface-doping technique by soaking the TiO2 film in acidic In3+ solution at 70 °C for 30, 45 and 60 min followed by sintering at 450 °C. Structural characterization of In-doped TiO2 films by SEM, TEM, EDX, XRD and Raman spectroscopy revealed the successful attachment of Indium to the surface of TiO2 and that the amount of In dopant is proportional to the soaking time. The PCE of the devices fabricated from In-doped TiO2 with a soaking time of 30 min produced an increase of 18.0 % compared to the undoped cells. Charge extraction analysis at open-circuit revealed that surface-doping with indium shifts TiO2 band edge downward. However, the increase in VOC was found as the net effect of negative movement of CB and retarded recombination caused by TiO2 surface passivation via the In dopant.

There is an increasing attention to develop Pt-free counter electrodes to further reduce the production cost of dye-sensitized solar cells (DSSCs). In this paper, we proposed a nanocomposite of a naturally derived carbon dot and cobalt sulfide which was prepared by a one-pot solvothermal method. The oxidation of the orange fiber and the formation of cobalt sulfide structures were confirmed by various characterization tools, such as thermogravimetric, energy-dispersive X-ray, X-ray powder diffraction and X-ray photoelectron spectroscopic analyses. The scanning electron microscopy and N2 porosimeter studies revealed nanoflake-like structures with an abundance of mesopores with a pore diameter of 4–15 nm. The electrocatalytic activity of the product obtained from electrochemical impedance spectroscopy was found to be close to that of Pt due to the increase of electrocatalytic active sites. Under the illumination of AM 1.5 simulated solar light, the DSSC based on the cobalt sulfide/carbon composite counter electrode achieves a power conversion efficiency of 5.94% which is higher than the Pt-based electrode (5.57%).

The gas-phase homolytic S–F bond dissociation energies (BDEs) of 21 sulfenyl-type fluorides (RSF) have been obtained using the W1w thermochemical protocol. The BDEs (at 298 K) for the species in this set range from 316.2 (HCCSF) to 368.1 (H2CCHSF) kJ mol–1. We additionally report fluorine-transfer energies (FTEs), corresponding to the energetics of fluorine transfer from RSF to H2S. At 298 K, the FTEs range from –10.7 (H2AlSF) to 90.7 (MeHNSF) kJ mol–1. We have also assessed the performance of a wide range of density functional theory (DFT) and double-hybrid DFT methods (in conjunction with the A'VQZ basis set) for the calculation of these quantities. For the calculation of S–F BDEs, the M06-2X procedure offers the best performance, with a mean absolute deviation (MAD) of 1.6 kJ mol–1, whilst for the FTEs, B2K-PLYP and DSD-PBEP86 offer the best performance with MADs of 0.5 kJ mol–1.

The PVdF-HFP nanofiber membranes with different molecular weight were prepared by electrospinning technique and were investigated as solid state electrolyte membranes in quasi solid state dye sensitized solar cells (QS-DSSC). The homogeneously distributed and fully interconnected nanofibers were obtained for all of the prepared PVdF-HFP electrospun membranes and the average fiber diameters of fabricated membranes were dependent upon the molecular weight of polymer. The thermal stability of electrospun PVdF-HFP membrane was decreased with a decrement of molecular weight, specifying the high heat transfer area of small diameter nanofibers. The QS-DSSC fabricated with the lower molecular weight PVdF-HFP electrospun nanofiber membrane exhibited the power conversion efficiency of 1 = 5.38%, which is superior over the high molecular weight membranes and is comparable with the liquid electrolyte. Furthermore, the electrospun PVdF-HFP membrane exhibited long-term durability over the liquid electrolyte, owing to the higher adsorption and retention efficiencies of liquid electrolyte in its highly porous and interconnected nanofibers. Thus the proposed electrospun PVdF-HFP membrane effectively tackled the volatilization and leakage of liquid electrolyte and provided good photoconversion efficiency associated with an excellent stability, which constructs the prepared electrospun membranes as credible solid state candidates for the application of QS-DSSCs.

One of the most significant aspects in the development of dye-sensitized solar cells is the exploration and design of high-efficiency and low-cost dyes. This paper reports the theoretical design of various triphenylamine analogues, wherein the central nitrogen moiety establishes an sp(2)-hybridization, which endows a significant participation in the charge-transfer properties. Density functional theory (DFT) and time-dependent DFT methodologies were utilized to investigate the geometry, electronic structure, photochemical properties, and electrochemical properties of these dyes. Different exchange-correlation functionals were initially evaluated to establish a proper methodology for calculating the excited-state energy of the reference dye, known as DIA3. Consequently, TD-LC-ωPBE with a damping parameter of 0.175 Bohr(-1) best correlates with the experimental value. Four new dyes, namely, Dhk1, Dhk2, Dhk3, and Dhk4, were designed by modifying the rigidity of the donor moiety. According to the results, altering the type and position of binding in the donor group leads to distinct planarity of the dyes, which significantly affects their properties. The designed Dhk4 dye showed more red-shifted and broadened absorption spectra owing to the enhanced coplanarity between its donor and π-bridge moiety, which brings an advantage for its potential use as sensitizer for photovoltaic applications.

The liquid phase of ethanol in pure and in non-polar solvents was studied at room temperature using Fourier transform infrared (FT-IR) and (1)H nuclear magnetic resonance (NMR) spectroscopies together with theoretical approach. The FT-IR spectra for pure ethanol and solution in cyclohexane at different dilution stages are consistent with (1)H NMR results. The results from both methods were best explained by the results of the density functional theory based on a multimeric model. It is suggested that cyclic trimers and tetramers are dominated in the solution of cyclohexane/hexane with the concentration greater than 0.5M at room temperature. In liquid ethanol, while the primary components at room temperature are cyclic trimers and tetramers, there is a certain amount (∼14%) of open hydroxide group representing the existence of chain like structures in the equilibria. The cyclic cluster model in the liquid and concentrated solution phase (0.5M) can be used to explain the anomalously lower freezing point of ethanol (159 K) than that of water (273 K) at ambient conditions. In addition, (1)H NMR at various dilution stages reveals the dynamics for the formation of cyclic clusters.