Lower Charge Recombination Research Articles

Synergizing tin dioxide/perovskite interface with fluorine-doped zinc oxide for stabilized and efficient carbon-based perovskite solar cells

The new generation of solar cell technology, perovskite solar cells (PSCs), are the most promising candidates to meet global energy demands. In the current study, we improved the efficiency of their cost-effective type, i.e., carbon-based PSCs, by employing an interface engineering on the tin dioxide (SnO2) electron transport layer (ETL). A fluorine doped-zinc oxide material was used to treat the SnO2 layer and prepare a better substrate for perovskite fabrication. The fabricated perovskite layer on the treated SnO2 reveals better charge transfer, lower charge recombination, and lower leakage current. In addition, the fabricated perovskite layer on the modified ETL showed improved crystalline properties with passivated grain boundaries. As a result, a champion efficiency of 15.22% was recorded for the target carbon-based PSCs, referring to improved photovoltaic performance. Notably, the target devices showed a higher stability behavior against ambient air and kept 95% of their initial efficiency after 1658 h ageing time.

Fabrication of ZnO/CuO nanoforests and their applicability to microbial photoelectrochemical cells

Three-dimensional ZnO/CuO nanoforests (NFRs) were fabricated via the galvanic submerged photosynthesis of crystallites in water at ambient temperature and pressure, and their photoelectrochemical (PEC) properties and applicability to microbial PEC (MPEC) cells were evaluated. ZnO/CuO NFRs irradiated with UV light for 48 h showed a high PEC current of − 2.9 ± 1.3 mA/cm2 and hydrogen (H2) generation rate of 0.63 ± 0.29 µmol/cm2/day at 0 V vs. RHE owing to their superior light absorption, large BET specific surface area, and low charge recombination. The biocompatibility of the ZnO/CuO NFRs was evaluated by assessing their influence on Escherichia coli MG1655 growth. The ZnO/CuO NFRs leached Cu2+ and inhibited bacterial growth after immersion in the medium. Cu elution could be prevented by maintaining the potential at 0.01 V vs. RHE. The ZnO/CuO NFRs can be used as photocathodes for PEC H2 generation and the MPEC-based synthesis of valuable CO2-reduction products.

Contrasting photocatalytic performance of quantum-dot sensitized p-type and n-type TiO2 hierarchical nanocomposites under visible light

In recent times, titanium dioxide (TiO2) has acquired greater attention owing to its efficient photocatalytic activity, low cost, stability, non-corrosive, high availability, and nontoxicity towards the environment and humans. However, two major drawbacks including a wide band gap of around ∼3.2 eV and a high recombination rate of the photogenerated charge carriers restrict its capability in practical application. In this work, we deposited metal chalcogenide-based quantum-dots of lead sulfide (PbS QDs) on P25-, p-type and n-type TiO2 nanoparticles by pseudo-successive ionic layer adsorption and reaction (p-SILAR) process to form hierarchical nanocomposite and studied the corresponding photocatalytic activity under visible light. Concurrently, improved optoelectronic characteristics were recorded for n-TiO2/PbS hierarchical nanocomposite due to low charge recombination evidenced from photoluminescence (PL) spectra and optimum PbS deposition evidenced from EDX analysis as compared to p-TiO2 and P25–TiO2. The n-TiO2/PbS hierarchical nanocomposite degrades 74.4% RhB dye under visible light in 120 min. The structural, morphological, and photocatalytic characteristics were investigated by scanning and transmission electron microscopy, PL spectra, UV–Vis spectrophotometry, and Fourier transforms infrared spectra. This work might offer new understandings on P25-, p- and n-TiO2/PbS hierarchical nanocomposites with improved photocatalytic performance for visible-light activated degradation of RhB.

The Role of Energy Offsets on Charge Photogeneration Dynamics in Y‐Series Molecules‐Based Polymer Solar Cells

Recent research has revealed that low‐energy offset polymer solar cells (PSCs) are capable of a power conversion efficiency of over 19%. However, it is unclear how energy offsets and the charge photogeneration process are correlated. Herein, the effect of energy offsets on charge photogeneration dynamics for Y‐series molecules (Y5, Y6, Y10, and BTP‐4F‐12)‐based PSCs with the variations of the lowest unoccupied molecular orbital energy offsets (ΔELUMO) of 0.11–0.42 eV and the highest occupied molecular orbital energy offsets (ΔEHOMO) of 0.08–0.23 eV utilizing steady‐state and time‐resolved spectroscopies is studied. The steady‐state measurement shows that the probability of photoluminescence quenching via energy transfer for the donor exciton reduces with the increasing ΔELUMO. It is found that even in PM6:Y6 with the highest ΔELUMO, ≈18% of PM6 exciton dissociated via the path of “energy transfer first and then hole transfer,” manifesting the energy transfer also plays a vital role in the process of exciton dissociation. Furthermore, it is found that the PM6 exciton can efficiently dissociate under the ΔELUMO of 0.11 eV. After photoexcitation of the Y‐series molecule acceptors, the exciton dissociation efficiency enhances with the increase of ΔEHOMO. Besides, the higher energy offsets, the lower charge recombination rate in the ultrafast timescale has been found from the transient absorption measurement. These findings reveal that energy offsets are important for charge photogeneration and recombination in an ultrafast timescale for Y‐series molecule‐based PSCs, which may shed light on the design of high‐performance PSCs.

Enhancing photoelectrochemical water oxidation activity of BiVO4 photoanode through the Co-catalytic effect of Ni(OH)2 and carbon quantum dots

The CQDs + Ni(OH)2/BiVO4 photoanode was fabricated by introducing CQDs with fluorescence and optical properties. The CQDs + Ni(OH)2/BiVO4 photoanode exhibited a low water oxidation onset potential (∼0.2 V vs. RHE) and a photocurrent density of 3.05 mA cm−2 at a voltage of 1.23 V vs. RHE, which is about 2.5 times than that of the unmodified BiVO4 electrode, and the charge injection efficiency is 65%. Surface dynamics test showed that CQDs + Ni(OH)2/BiVO4 photoanode had higher charge transfer rate and lower charge recombination rate than BiVO4 electrode. As a cheap and stable catalyst for water oxidation, Ni(OH)2 combined with CQDs can effectively improve the migration of photogenerated electrons and holes, thereby improving the photoelectrochemical (PEC) water oxidation activity of the photoanode.

Waste ilmenite sludge-derived low-cost mesoporous Fe-doped TiO2: A versatile photocatalyst for enhanced visible light photocatalysis without a cocatalyst

Ilmenite (FeTiO3), a waste of the titania production industry, is proposed as a potential candidate for visible-light-driven photocatalysis due to its narrow band gap (Eg = 2.01–2.90 eV). However, to date, its photocatalytic performance has been very poor, even significantly lower than TiO2 (Eg = 3.2 eV) due to its high iron content. Herein we report waste ilmenite sludge-derived mesoporous Fe-doped titania (m-FDT) photocatalyst with significantly enhanced activity for a variety of photocatalytic processes, including photocatalytic CO2 reduction, water splitting, and dye-degradation. The m-FDT is developed via a simple hydrothermal process and has desirable properties such as a low band gap (1.72 eV), high surface area (137 m2/g), and lower charge recombination. This can be attributed to the formation of various defects (Fe2+, Fe3+, Ti3+, and O vacancies) due to the doping of Fe in the TiO2 lattice, as confirmed by various experiments and theoretical studies. The champion photocatalyst with an optimal Fe content (1.8 wt%) exhibits high methanol production (86.1 mmol/gcat), which is 100-fold higher than commercial TiO2 without noble metal cocatalyst and sacrificial agent. The designed photocatalyst shows excellent water-splitting activity (55.03 μmol/gcat) and dye degradation ability. This work presents a high-performance, low-cost, versatile photocatalyst for visible light photocatalysis and opens new avenues in semiconductor photocatalysis.

Indolocarbazole-based small molecules as guest donors for High-Performance ternary organic photovoltaics

This study explores the use of A-D-A or A-D-A′-type small molecule donors that contain an indolocarbazole-based moiety with both symmetric and asymmetric structures as the third component in PM6:Y6 systems to develop ternary organic photovoltaics (OPVs). The guest donor, Ema-OEt, was found to be highly miscible with Y6, resulting in an optimized morphology of an alloy-like structure in the blended film. This, in turn, led to balanced charge transport, high charge mobility, and low charge recombination in the devices, resulting in a synergistic improvement in PV parameters, ultimately leading to an advanced power conversion efficiency (PCE) of 17.64 % in the optimized (PM6:Ema-OEt:Y6 = 1: 0.07: 1.2) ternary device. Furthermore, despite having a higher HOMO energy level than PM6, Ema-OEt, doped as a guest donor in the ternary OPV device, demonstrated a remarkable indoor PCE of 28.67 % under TL84 (Pin = 311.9 μW cm−2). These findings provide an effective and innovative approach to enhance the performance of OPVs.

Photoelectric Conversion and Device Stability of PM6:PY-IT Solar Cells Based on a Water Solution-Processed MoO3 Hole Transport Layer.

To enhance the power conversion efficiency (PCE) and stability of all-polymer solar cells (all-PSCs), a new precursor solution based on an in situ chemical reaction of nanomolybdenum powder (Mo), hydrogen peroxide (H2O2), and ammonia (NH3·H2O) was developed for preparing a MoO3 hole transport layer (HTL) for all-PSCs. The results showed that the PCE and stability of PM6:PY-IT solar cells based on the MoO3 HTL were better than those based on a PEDOT:PSS layer. To further understand the relationship between the HTL and the device performance, ultrafast photophysical processes of all-PSCs based on different HTLs were contrastively analyzed. Our research indicated that the micromorphology of active layers could be influenced by the interfacial layer material, consequently determining the photoelectric conversion process of all-PSCs. The MoO3-based all-PSCs had longer charge lifetime, higher charge mobility, and lower charge recombination characteristics compared with the devices based on the PEDOT:PSS layer during the operation time. As a result, the MoO3-based PM6:PY-IT solar cells achieved an initial PCE of 15.2%, and they still maintained more than 80% of their initial efficiency after 1000 h.

Anchoring porphyrin self-assembled dye sensitized solar cells: synthesis and photovoltaic application

Anchoring porphyrin, ZnPAc, featuring cyanoacetic acid group has been synthesized for application in a dye-sensitized solar cell. Capping layer dyes zinc meso-tetraphenyl porphyrin (ZnTPP) with anchoring porphyrin ZnPAc through axial coordination bonds of Zn-to-ligand self-assembles solar cell devices. With the introduction of cyanoacetic acid anchor, the higher electrons are effectively injected into the TiO2 semiconductor surface. Thus, the ZnTPP-ZnPAc-based device has more short-circuit current (JSC ) compared with our previously reported ZnTPP-ZnPA-based solar cell. The ZnPA and ZnPAc porphyrin anchoring dyes maintain a broad absorption spectrum and also improve electron injection and lower charge recombination compared to our previous reports on organic molecule anchored dye W3. Hence, the ZnTPP-ZnPAc self-assembled dye has higher power conversion efficiency. The assembled modes were also verified by transmission electron microscopy (TEM). To understand ZnTPP-ZnPAc for photovoltaic performance trends, we have carried out charge extraction, transient photovoltage decay and electrochemical impedance spectroscopy analysis.

Synthesis of binary metal doped CeO2 via the subcritical hydrothermal method for photo-mineralizing methyl orange dye

Herein, we adopted subcritical hydrothermal method to synthesize the copper and bismuth co-doped CeO2 (Ce0.92Cu0.04Bi0.04O2) nanostructure for water remediation application. Copper and Bismuth co-doping synergistically improved the current conductivity and light-harvesting capabilities of the co-doped CeO2 that is respectively confirmed through current-voltage and optical studies. The microstructural, compositional and morphological information of the as-synthesized photocatalyst were accessed through powder XRD, and electronics spectroscopic techniques. In terms of practical application, the as-prepared co-doped CeO2-based photocatalyst mineralized the anionic dye (methyl orange, MO) up to 95.79%, at the rate of 0.0314 min−1, in just 50 min of solar irradiation. Statistics show that our Ce0.92Cu0.04Bi0.04O2 photocatalyst is 2.32 times more effective at mineralizing MO dye, and its rate of dye mineralization is 5.5 times faster than a CeO2 photocatalyst. In addition, the Ce0.92Cu0.04Bi0.04O2 photocatalyst possesses exceptional robustness as it fully retains its photocatalytic activity after three consecutive reusability tests. Our doped photocatalyst's excellent dye mineralizing activities come from the way its hybrid nanostructure morphology, good current conductivity, visible-light-supported bandgap, and induced structural defects work together. This gives it a larger surface area, a faster charge transport rate, better light harvesting ability, and lower charge recombination efficiencies. The copper and bismuth co-doping in the CeO2 lattice have a positive effect on its photocatalytic properties, suggesting that it has the potential to be a light-driven catalyst for azo dyes degradation.

Application of Newly Designed Y‐Series Nonfullerene Acceptors for High‐Efficient Organic Solar Cells

AbstractThe electron acceptor materials in organic solar cells (OSCs) play an essential role in enhancing power conversion efficiency (PCE). Although Y6‐based nonfullerene acceptors (NFAs) have shown fascinating experimental progress, molecular engineering is an effective strategy for further improvement of PCE. Herein, a series of Y6‐based symmetric and asymmetric NFAs are designed using the Y6‐based core with various end‐group units. The impact of end group units on geometric, electronic, and excited state properties of NFAs is studied using state‐of‐the‐art density functional theory methods. Various selection criteria are used to screen potential NFAs among 18 newly designed NFAs. The interfacial electronic properties between conjugated polymer and NFAs are thoroughly studied in the excited state to analyze the potentiality of screened NFAs. More importantly, the screened asymmetric NFAs have shown improved charge mobilities with a lower charge recombination rate than prototype FRY6. It is noticed that screened NFAs have multiple charge transfer pathways through direct excitation, hot excitons, and intermolecular electric field mechanisms. Overall, the results obtained from this computational study give useful guidance for developing NFAs for high‐performance OSCs.

Effects of iron oxide contents on photocatalytic performance of nanocomposites based on g-C3N4

α-Fe2O3/Fe3O4/g-C3N4 nanocomposites were prepared in-situ by solution combustion as magnetically separable photocatalysts using ferric nitrate as oxidant, glycine as organic fuel, and g-C3N4. The effects of various amounts of iron oxides, on the magnetic, optical, and photocatalytic properties were explored by different characterization methods. The magnetite (Fe3O4) phase as ferrimagnetic material disappeared with the increase in ferric nitrate contents, leading to the decrease of magnetic properties. The bandgap energy decreased from 2.8 to 1.6 eV with the increase of the hematite (α-Fe2O3) phase.The photocatalytic results showed that the type and amount of iron oxides had a significant effect on the decolorization of methylene blue, rhodamine B and methyl orange dyes under visible-light irradiation. The activity of the nanocomposite sample containing 37 wt. % iron oxides was more effective than that of the pristine g-C3N4 sample to photodegrade the methylene blue, rhodamine B and methyl orange, respectively. Moreover, the nanocomposites exhibited a higher photocurrent density than that of the pristine g-C3N4, mainly due to their lower charge recombination rate.

Photocatalytic conversion of MB dye using Co3O4 QDs‐Ag2MoO4 as an active heterojunction photocatalyst under visible light irradiation

Herein, the preparation of Co3O4 QDs‐Ag2MoO4 (AMO) heterojunction was reported by a facile hydrothermal method and characterized by physicochemical methods such as Fourier transformed infrared (FT‐IR), X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM), differential reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and UV–Vis. The SEM images show that AMO particles and Co3O4 QDs‐AMO have a morphology of 3D‐hexagons and nanosheets accumulated on the surface of 3D‐hexagons with an average of 36 and 28 nm in size, respectively. The Co3O4 QDs‐AMO photocatalyst was used toward the conversion of methylene blue with a removal percentage of 91%, which is 15 times more than pure AMO. The higher photoactivity of Co3O4 QDs‐AMO heterojunction should be assigned to its lower charge recombination rate compared with pure AMO nanoparticles. This heterojunction photocatalyst was removed from the mixture reaction and reused five times without a considerable decline in activity. Furthermore, a postulated mechanism by the hydroxyl radical (°OH) path was proposed.

Simultaneous S-scheme promoted Ag@AgVO3/g-C3N4/CeVO4 heterojunction with enhanced charge separation and photo redox ability towards solar photocatalysis

Photocatalytic removal of toxic contaminants is one of the emerging techniques for water remediation, but it suffers from low redox ability, charge recombination and poor light harvesting efficiency. The present work reports a simultaneous S-scheme promoted by CeVO4/g-C3N4/Ag@AgVO3. The formation of the S-scheme mechanism enhanced the generation of photogenerated carriers and also improved the redox ability of the electrons and holes in the reduction and oxidation photocatalysts. The ternary demonstrated remarkable photo switching properties along with efficient charge separation which was achieved through dual interfacial interaction within the ternary (Ag@AgVO3/g-C3N4 and CeVO4/g-C3N4). The heterojunction formation was verified through the shift in binding energy spectra in the X-ray Photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy analysis (HR-TEM). The ternary demonstrated reduced PL intensity, width of space charge region and an upsurge in photogenerated current density in the order of 93 μA/cm2 (∼6X higher than all the pristine). This resulted in efficient removal of methyl orange, methylene blue and endocrine disruptive bisphenol-A with a removal rate of 0.02 min−1, 0.03 min−1 and 0.0087 min−1 and an apparent quantum yield of 4.6 × 10−9 (Methylene Orange), 6.89 × 10−9 (Methylene Blue) and 2 × 10−9 (Bisphenol A/H2O2).

Modulating light absorption and charge recombination in photoelectrochemical water oxidation with spin-coated MoS2 co-catalyst on ZnO nanorods

Efficient oxygen evolution reaction (OER) on a photoanode is until today considered a major challenge. In the case of ZnO, one of the most investigated semiconductors, the limitation is due to its low visible light absorption and severe charge recombination. Combining ZnO with catalytically active 2D materials such as MoS2 has been proven to increase its water oxidation performance, but they are still often produced using complex methods. Here, we present a simple and low-cost method of spin-coating to fabricate ZnO nanorods/MoS2 nanosheets (ZRM) heterostructures for OER photoanode. Using this method, we successfully produce heterostructures with improved performance, that is, measured photocurrent density (Jph) of 0.61 mA cm−2 at 1.23 V vs. RHE, about threefold than that of pure ZnO, with excellent photostability, which is on par with similar heterostructures synthesized using more complex methods. Beyond benchmarking the performance, we also unravel the mechanism by which MoS2 improves the water oxidation process, that is, through the efficient light-harvesting (ηLHE), charge separation (ηsep), and charge injection (ηinj). Our findings provide a straightforward route to produce metal oxide/2D materials heterostructure-based photoanodes for photoelectrochemical water splitting.

Potassium-Derived Charge Channels in Boron-Doped g-C3N4 Nanosheets for Photocatalytic NO Oxidation and Hydrogen Evolution.

The application of graphitic carbon nitride (g-C3N4) in photocatalytic NO oxidation was limited due to severe recombination of photogenerated carriers and low concentration of oxidizing species. In this work, K and B were introduced into the interlayer and in-plane framework of g-C3N4 to address this challenge through the thermal polymerization process. The synthesized K-doped B-g-C3N4 nanosheets exhibited expanded light absorption and low charge recombination efficiency. In addition, the doping of K and B reduced the band gap of g-C3N4, which corresponded to enhanced light absorption. B was introduced into the in-plane structure by replacing C atoms, which adjusted the in-plane electron distribution. K was inserted into the interlayer by binding to the N and C atoms of adjacent layers. K-derived electron transfer channels were constructed, which increased electron delocalization and expanded the π-conjugate system. More electrons were transferred through the interlayer channels and were involved in the reaction process. The severe carrier recombination and weak transfer were improved due to the synergistic effect of K and B doping. K-doped B-g-C3N4 nanosheets exhibited enhanced generation of superoxide radicals and hydroxyl radicals, which played a key role during NO oxidation. The photocatalytic NO oxidation efficiency of codoped g-C3N4 nanosheets reached 61%, which was 2.1 and 1.2 times of that of pristine g-C3N4 and B-doped g-C3N4, respectively. The codoped g-C3N4 sample still exhibited stable photocatalytic NO oxidation efficiency after five cycles. This result provided a potential idea for improving the charge distribution and transfer of layered materials by codoping metallic and nonmetallic elements and for photocatalytic NO oxidation.

UV light-induced oxygen doping in graphitic carbon nitride with suppressed deep trapping for enhancement in CO2 photoreduction activity

• Oxygen (O) element is introduced in the bulk graphitic carbon nitride (CN) for the first time through a precursor pretreatment by ultraviolet (UV) light irradiation. • The doped O non-metal photocatalyst of CN increased visible light absorption and enhanced carrier density. • The optimized sample has lower charge recombination and suppressed electron deep trapping. • The optimized sample shows enhanced photoreduction activity of CO2 to CH4. While photoreduction of CO 2 to CH 4 is an effective means of producing value-added fuels, common photocatalysts have poor activity and low selectivity in photocatalytic CO 2 -reduction processes. Even though creating defects is an effective photocatalyst fabrication route to improve photocatalytic activity, there are some challenges with the facile photocatalyst synthesis method. In this work, an O element is introduced into a graphitic carbon nitride (CN) skeleton through a precursory ultraviolet light irradiation pretreatment to increase the visible light absorption and enhance the carrier density of this modified non-metal CN photocatalyst; the charge transfer dynamics thereof are also studied through electrochemical tests, photoluminescence spectroscopy, and nanosecond transient absorption. We verify that the optimized sample exhibits lower charge recombination and a suppressed 84 ns electron-trapping lifetime, compared to the 103 ns electron-trapping lifetime of the CN counterpart, and thereby contributes to robust detrapping and a fast transfer of active electrons. Through density functional theory calculations, we find that the improved light absorption and increased electron density are ascribed to O-element doping, which enhances the CO 2 adsorption energy and improves the CO 2 -to-CH 4 photoreduction activity; it becomes 17 times higher than that of the bare CN, and the selectivity is 3.8 times higher than that of CN. Moreover, the optimized sample demonstrates excellent cyclic stability in a 24-hour cycle test.

Simultaneously enhancing the photovoltaic parameters of ternary organic solar cells by incorporating a fused ring electron acceptor.

The ternary strategy has been recognized as an effective method to improve the photovoltaic performance of organic solar cells (OSCs). In ternary OSCs, the complementary or broadened absorption spectrum, optimized morphology, and enhanced photovoltaic performance could be obtained by selecting a third rational component for the host system. In this work, a fused ring electron acceptor named BTMe-C8-2F, which possesses a high-lying lowest unoccupied molecular orbital (LUMO) energy level and a complementary absorption spectrum to PM6:Y6, was introduced to a PM6:Y6 binary system. The ternary blend film PM6:Y6:BTMe-C8-2F showed high and more balanced charge mobilities, and low charge recombination. Therefore, the OSC based on the PM6:Y6:BTMe-C8-2F (1 : 1.2 : 0.3, w/w/w) blend film achieved the highest power conversion efficiency (PCE) of 17.68%, with an open-circuit voltage (VOC) of 0.87 V, a short-circuit current (JSC) of 27.32 mA cm-2, and a fill factor (FF) of 74.05%, which are much higher than the binary devices of PM6:Y6 (PCE = 15.86%) and PM6:BTMe-C8-2F (PCE = 11.98%). This work provides more insight into the role of introducing a fused ring electron acceptor with a high-lying LUMO energy level and complementary spectrum for simultaneously enhancing the VOC and JSC to promote the performance of ternary OSCs.

Optimizing the performance of Auy/Nix/TiO2NTs photoanodes for photoelectrochemical water splitting.

Water splitting using photoelectrochemical (PEC) techniques is thought to be a potential method for creating green hydrogen as a sustainable energy source. How to create extremely effective electrode materials is a pressing concern in this area. In this work, a series of Nix/TiO2 anodized nanotubes (NTs) and Auy/Nix/TiO2NTs photoanodes were prepared by electrodeposition via cyclic voltammetry and UV-photoreduction, respectively. The photoanodes were characterized by several structural, morphological, and optical techniques and their performance in PEC water-splitting for oxygen evolution reaction (OER) under simulated solar light was investigated. The obtained results revealed the nanotubular structure of TiO2NTs was preserved after deposition of NiO and Au nanoparticles while the band gap energy was reduced allowing for effective utilization of solar light with lower charge recombination rate. The PEC performance was monitored and it was found that the photocurrent densities of Ni20/TiO2NTs and Au30/Ni20/TiO2NTs were 1.75-fold and 3.25-fold that of pristine TiO2NTs, respectively. It was confirmed that the performance of the photoanodes depends on the number of electrodeposition cycles and duration of photoreduction of gold salt solution. The observed enhanced OER activity of Au30/Ni20/TiO2NTs could be attributed to the synergism between the local surface plasmon resonance (LSPR) effect of nanometric gold which increased solar light harvesting and the p-n heterojunction formed at the NiO/TiO2 interface which led to better charge separation and transportation suggesting its potential application as an efficient and stable photoanode in PEC water splitting for H2 production.

Environmentally affable and highly efficient donor material based on cyclopentadithiophene (CPDT) framework for remarkable organic solar cells

The quantum chemical exploration of highly conjugated D-π-A type molecules based on cyclopentadithiophene (CPDT) core is anticipated to recommend novel organic materials for efficient organic solar cells (OSCs). Five new conjugated molecules (C1–C5) were designed by drafting of reference CR through thiophene bridged end caped acceptors and their geometric, as well as optoelectronic properties, were investigated at MPW1PW91/6-31G (d,p) functional. All the newly tailored chromophores (C1–C5) proclaimed lower energy gap values (ranging from 1.95 to 2.19 eV) than the reference CR (3.18 eV). TD-DFT calculations of all the newly designed molecules revealed higher λmax in the range 500–514 nm than the reference CR (483.2 nm) in dichloromethane solvent. Lower excitation energies (1.79–1.94 eV) and higher dipole moment (4.84–18.37 D) for all the drafted compounds (C1–C5) than reference CR were observed which proclaimed efficient charge transfer. Simulations of global reactivity parameters like hardness, chemical potential, softness and electrophilicity manifested all these molecules (C1–C5) to be reactive and thermally stable. The small values of reorganization energies for electron and hole exhibited high electron-hole mobilities and low charge recombination. The power conversion efficiency (PCE) parameters were simulated by scaling the HOMO of designed molecules acting as a donor with LUMO of PC61BM acceptor. All the designed molecules (C1–C5) demonstrated high open circuit voltage (0.67–0.92 V) than the reference (0.49 V) which is favorable for enhancement of PCE. Also, the higher values of fill factor (FF) ranging from 0.8417 to 0.8677 for newly designed chromophores increased the PCE than reference CR (0.8015). The results demonstrated the suitability of these donor molecules designed by deliberated technique, opening a new path for the development of donor's contributors to OSCs and may prove efficient materials for fabrication of future OSCs.