613 results found
Wang Y, Godin R, Durrant JR, et al., 2021, Efficient Hole Trapping in Carbon Dot/Oxygen‐Modified Carbon Nitride Heterojunction Photocatalysts for Enhanced Methanol Production from CO 2 under Neutral Conditions, Angewandte Chemie, Vol: 133, Pages: 20979-20984, ISSN: 0044-8249
Lin C-T, Xu W, Macdonald T, et al., 2021, Correlating active layer structure and composition with device performance and lifetime in amino acid modified perovskite solar cells, ACS Applied Materials and Interfaces, ISSN: 1944-8244
Additive engineering is emerging as a powerful strategy to further enhance the performance of perovskite solarcells (PSCs), with the incorporation of bulky cations and amino acid (AA) derivatives being shown as a promisingstrategy for enhanced device stability. However, the incorporation of such additives typically results inphotocurrent losses owing to their saturated carbon backbones hindering charge transport and collection. Herewe investigate the use of amino acids with varying carbon chain lengths as zwitterionic additives that enhancePSC device stability, in air and nitrogen, under illumination. We discover thatstability is insensitive to chain lengthhowever, as anticipated photocurrent drops as chain length increases. Using glycine as an additive results in animprovement in open circuit voltage from 1.10 to 1.14 V and a resulting power conversion efficiency of 20.2%(20.1% stabilized). Using time-of-flight secondary ion mass spectrometry we confirm that the AAs reside at thesurfaces and interfaces of our perovskite films and propose the mechanisms by which stability is enhanced. Wehighlight this with glycine as an additive, whereby an 8-fold increase in device lifetime in ambient air at 1-sunillumination is recorded. Short circuit photoluminescence quenching of complete devices are reported and revealthat the loss in photocurrent density observed with longer carbon chain AAs results from inefficient chargeextraction from the perovskite absorber layer. These combined results demonstrate new fundamentalunderstandings in the photophysical processes of additive engineering using amino acids and provide asignificant step forward in improving the stability of high-performance PSCs.
Wang Y, Godin R, Durrant JR, et al., 2021, Efficient Hole Trapping in Carbon Dot/Oxygen-Modified Carbon Nitride Heterojunction Photocatalysts for Enhanced Methanol Production from CO2 under Neutral Conditions, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, ISSN: 1433-7851
Corby S, Rao R, Steier L, et al., 2021, The kinetics of metal oxide photoanodesfrom charge generation to catalysis, Nature Reviews Materials, ISSN: 2058-8437
Generating charge carriers with lifetimes long enough to drive catalysis is a critical aspect for both photoelectrochemical and photocatalytic systems and a key determinant of their efficiency. This review addresses the charge carrier dynamics underlying the performance of metal oxides as photoanodes and their ability to drive photoelectrochemical water oxidation, alongside wider comparison with metal oxide function in photocatalytic and electrocatalytic systems. We start by highlighting the disparity between the ps–ns lifetimes of electron and holes photoexcited in bulk metal oxides versus the ms –s timescale of water oxidation catalysis. We go onto review recent literature of the dominant kinetic processes determining photoanode performance, namely charge generation, polaron formation and charge trapping, bulk and surface recombination, charge separation and extraction, and finally the kinetics of water oxidation catalysis. With each topic, we review current understanding and note areas of remaining uncertainty or controversy. We discuss the potential for material selection and examine approaches such as doping, nanostructuring, junction formation and/or co-catalyst deposition to enhance performance. Critically, we examine how such performance enhancements can be understood from analyses of carrier dynamics and propose design guidelines for further material or device optimisation.
Adler C, Selim S, Krivtsov I, et al., 2021, Photodoping and Fast Charge Extraction in Ionic Carbon Nitride Photoanodes, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X
Murali G, Modigunta JKR, Park S, et al., 2021, Enhancing Light Absorption and Prolonging Charge Separation in Carbon Quantum Dots via CI-Doping for Visible-Light-Driven Photocharge-Transfer Reactions, ACS APPLIED MATERIALS & INTERFACES, Vol: 13, Pages: 34648-34657, ISSN: 1944-8244
Clarke AJ, Luke J, Meitzner R, et al., 2021, Non-fullerene acceptor photostability and its impact on organic solar cell lifetime, CELL REPORTS PHYSICAL SCIENCE, Vol: 2, ISSN: 2666-3864
Chang Y-H, Carron R, Ochoa M, et al., 2021, Impact of RbF and NaF Postdeposition Treatments on Charge Carrier Transport and Recombination in Ga-Graded Cu(In,Ga)Se-2 Solar Cells, ADVANCED FUNCTIONAL MATERIALS, ISSN: 1616-301X
Du T, Ratnasingham SR, Kosasih FU, et al., 2021, Aerosol assisted solvent treatment: a universal method for performance and stability enhancements in perovskite solar cells, Advanced Energy Materials, ISSN: 1614-6832
Metal-halide perovskite solar cells (PSCs) have had a transformative impact on the renewable energy landscape since they were first demonstrated just over a decade ago. Outstanding improvements in performance have been demonstrated through structural, compositional, and morphological control of devices, with commercialization now being a reality. Here the authors present an aerosol assisted solvent treatment as a universal method to obtain performance and stability enhancements in PSCs, demonstrating their methodology as a convenient, scalable, and reproducible post-deposition treatment for PSCs. Their results identify improvements in crystallinity and grain size, accompanied by a narrowing in grain size distribution as the underlying physical changes that drive reductions of electronic and ionic defects. These changes lead to prolonged charge-carrier lifetimes and ultimately increased device efficiencies. The versatility of the process is demonstrated for PSCs with thick (>1 µm) active layers, large-areas (>1 cm2) and a variety of device architectures and active layer compositions. This simple post-deposition process is widely transferable across the field of perovskites, thereby improving the future design principles of these materials to develop large-area, stable, and efficient PSCs.
Jones B, Davies KR, Allan MG, et al., 2021, Photoelectrochemical concurrent hydrogen generation and heavy metal recovery from polluted acidic mine water, SUSTAINABLE ENERGY & FUELS, Vol: 5, Pages: 3084-3091, ISSN: 2398-4902
Bucci A, Garcia-Tecedor M, Corby S, et al., 2021, Self-supported ultra-active NiO-based electrocatalysts for the oxygen evolution reaction by solution combustion, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 12700-12710, ISSN: 2050-7488
Kyeong M, Lee J, Daboczi M, et al., 2021, Organic cathode interfacial materials for non-fullerene organic solar cells, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 9, Pages: 13506-13514, ISSN: 2050-7488
Francas L, Selim S, Corby S, et al., 2021, Water oxidation kinetics of nanoporous BiVO4 photoanodes functionalised with nickel/iron oxyhydroxide electrocatalysts, CHEMICAL SCIENCE, Vol: 12, Pages: 7442-7452, ISSN: 2041-6520
Moss B, Wang Q, Butler K, et al., 2021, Linking in situ charge accumulation to electronic structure in doped SrTiO3 reveals design principles for hydrogen-evolving photocatalysts, Nature Materials, Vol: 20, Pages: 511-517, ISSN: 1476-1122
Recently, high solar-to-hydrogen efficiencies were demonstrated using La and Rh co-doped SrTiO3 (La,Rh:SrTiO3) incorporated into a low-cost and scalable Z-scheme device, known as a photocatalyst sheet. However, the unique properties that enable La,Rh:SrTiO3 to support this impressive performance are not fully understood. Combining in situ spectroelectrochemical measurements with density functional theory and photoelectron spectroscopy produces a depletion model of Rh:SrTiO3 and La,Rh:SrTiO3 photocatalyst sheets. This reveals remarkable properties, such as deep flatband potentials (+2 V versus the reversible hydrogen electrode) and a Rh oxidation state dependent reorganization of the electronic structure, involving the loss of a vacant Rh 4d mid-gap state. This reorganization enables Rh:SrTiO3 to be reduced by co-doping without compromising the p-type character. In situ time-resolved spectroscopies show that the electronic structure reorganization induced by Rh reduction controls the electron lifetime in photocatalyst sheets. In Rh:SrTiO3, enhanced lifetimes can only be obtained at negative applied potentials, where the complete Z-scheme operates inefficiently. La co-doping fixes Rh in the 3+ state, which results in long-lived photogenerated electrons even at very positive potentials (+1 V versus the reversible hydrogen electrode), in which both components of the complete device operate effectively. This understanding of the role of co-dopants provides a new insight into the design principles for water-splitting devices based on bandgap-engineered metal oxides.
Mohapatra AA, Dong Y, Boregowda P, et al., 2021, Rational design of donor-acceptor based semiconducting copolymers with high dielectric constants, The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, Vol: 125, Pages: 6886-6896, ISSN: 1932-7447
The low dielectric constant of organic semiconductors limits the efficiency of organic solar cells (OSCs). In an attempt to improve the dielectric constant of conjugated polymers, we report the synthesis of three semiconducting copolymers by combining the thiophene-substituted diketopyrrolopyrrole (TDPP) monomer with three different monomeric units with varying electron donating/accepting strengths: benzodithiophene (BBT-3TEG-TDPP), TDPP (TDPP-3TEG-TDPP), and naphthalene diimide (P(gNDI-TDPP)). Among the series, BBT-3TEG-TDPP and P(gNDI-TDPP) exhibited the highest dielectric constants (∼5) at 1 MHz frequency, signifying the contribution of dipolar polarization from TEG side-chains. Furthermore, transient absorption spectroscopic studies performed on these polymers indicated low exciton diffusion length as observed in common organic semiconducting polymers. Our findings suggest that utilizing the polar side-chains enhances the dielectric constant in a frequency regime of megahertz. However, it is not sufficient to reduce the Coulombic interaction between hole and electron in excitonic solar cells.
Chang Y-H, Carron R, Ochoa M, et al., 2021, Insights from transient absorption spectroscopy into electron dynamics along the Ga-gradient in Cu(In,Ga)Se2 solar cells, Advanced Energy Materials, Vol: 11, ISSN: 1614-6832
Cu(In,Ga)Se2 solar cells have markedly increased their efficiency over the last decades currently reaching a record power conversion efficiency of 23.3%. Key aspects to this efficiency progress are the engineered bandgap gradient profile across the absorber depth, along with controlled incorporation of alkali atoms via post‐deposition treatments. Whereas the impact of these treatments on the carrier lifetime has been extensively studied in ungraded Cu(In,Ga)Se2 films, the role of the Ga‐gradient on carrier mobility has been less explored. Here, transient absorption spectroscopy (TAS) is utilized to investigate the impact of the Ga‐gradient profile on charge carrier dynamics. Minority carriers excited in large Cu(In,Ga)Se2 grains with a [Ga]/([Ga]+[In]) ratio between 0.2–0.5 are found to drift‐diffuse across ≈1/3 of the absorber layer to the engineered bandgap minimum within 2 ns, which corresponds to a mobility range of 8.7–58.9 cm2 V−1 s−1. In addition, the recombination times strongly depend on the Ga‐content, ranging from 19.1 ns in the energy minimum to 85 ps in the high Ga‐content region near the Mo‐back contact. An analytical model, as well as drift‐diffusion numerical simulations, fully decouple carrier transport and recombination behaviour in this complex composition‐graded absorber structure, demonstrating the potential of TAS.
Limbu S, Park K-B, Wu J, et al., 2021, Identifying the Molecular Origins of High-Performance in Organic Photodetectors Based on Highly Intermixed Bulk Heterojunction Blends, ACS NANO, Vol: 15, Pages: 1217-1228, ISSN: 1936-0851
Bozal-Ginesta C, Mesa CA, Eisenschmidt A, et al., 2021, Charge accumulation kinetics in multi-redox molecular catalysts immobilised on TiO2, CHEMICAL SCIENCE, Vol: 12, Pages: 946-959, ISSN: 2041-6520
Rao RR, Stephens IEL, Durrant JR, 2021, Understanding What Controls the Rate of Electrochemical Oxygen Evolution, JOULE, Vol: 5, Pages: 16-18, ISSN: 2542-4351
Wilson AA, Corby S, Francas L, et al., 2021, The effect of nanoparticulate PdO co-catalysts on the faradaic and light conversion efficiency of WO3 photoanodes for water oxidation, Physical Chemistry Chemical Physics, Vol: 23, Pages: 1285-1291, ISSN: 1463-9076
WO3 photoanodes offer rare stability in acidic media, but are limited by their selectivity for oxygen evolution over parasitic side reactions, when employed in photoelectrochemical (PEC) water splitting. Herein, this is remedied via the modification of nanostructured WO3 photoanodes with surface decorated PdO as an oxygen evolution co-catalyst (OEC). The photoanodes and co-catalyst particles are grown using an up-scalable aerosol assisted chemical vapour deposition (AA-CVD) route, and their physical properties characterised by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and UV-vis absorption spectroscopy. Subsequent PEC and transient photocurrent (TPC) measurements showed that the use of a PdO co-catalyst dramatically increases the faradaic efficiency (FE) of water oxidation from 52% to 92%, whilst simultaneously enhancing the photocurrent generation and charge extraction rate. The Pd oxidation state was found to be critical in achieving these notable improvements to the photoanode performance, which is primarily attributed to the higher selectivity towards oxygen evolution when PdO is used as an OEC and the formation of a favourable junction between WO3 and PdO, that drives band bending and charge separation.
Sachs M, Cha H, Kosco J, et al., 2021, Tracking Charge Transfer to Residual Metal Clusters in Conjugated Polymers for Photocatalytic Hydrogen Evolution (vol 142, pg 14574, 2020), JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 143, Pages: 524-524, ISSN: 0002-7863
Nikolis VC, Dong Y, Kublitski J, et al., 2020, Field Effect versus Driving Force: Charge Generation in Small-Molecule Organic Solar Cells, ADVANCED ENERGY MATERIALS, ISSN: 1614-6832
Mesa CA, Rao RR, Francas L, et al., 2020, Reply to: Questioning the rate law in the analysis of water oxidation catalysis on haematite photoanodes, NATURE CHEMISTRY, Vol: 12, Pages: 1099-+, ISSN: 1755-4330
Corby S, Tecedor M-G, Tengeler S, et al., 2020, Separating bulk and surface processes in NiO(x)electrocatalysts for water oxidation, SUSTAINABLE ENERGY & FUELS, Vol: 4, Pages: 5024-5030, ISSN: 2398-4902
Dong Y, Nikolis VC, Talnack F, et al., 2020, Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic sol, Nature Communications, Vol: 11, ISSN: 2041-1723
Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control.
Aitchison CM, Sachs M, Little MA, et al., 2020, Structure-activity relationships in well-defined conjugated oligomer photocatalysts for hydrogen production from water, CHEMICAL SCIENCE, Vol: 11, Pages: 8744-8756, ISSN: 2041-6520
Moss B, Le H, Corby S, et al., 2020, Anisotropic electron transport limits performance of Bi2WO6 photoanodes, The Journal of Physical Chemistry C, Vol: 124, Pages: 18859-18867, ISSN: 1932-7447
Bi2WO6 is one of the simplest members of the versatile Aurivillius oxide family of materials. As an intriguing model system for Aurivillius oxides, BiVO4 exhibits low water oxidation onset potentials (∼0.5–0.6 VRHE) for driven solar water oxidation. Despite this, Bi2WO6 also produces low photocurrents in comparison to other metal oxides. Due to a lack of in situ studies, the reasons for such poor performance are not understood. In this study, Bi2WO6 photoanodes are synthesized by aerosol-assisted chemical vapor deposition. The charge carrier dynamics of Bi2WO6 are studied in situ under water oxidation conditions, and the rate of both bulk recombination and water oxidation is found to be comparable to other metal oxide photoanodes. However, the rate of electron extraction is at least 10 times slower than the slowest kinetics previously reported in an oxide photoanode. First-principles analysis indicates that the slow electron extraction kinetics are linked to a strong anisotropy in the conduction band. Preferred or epitaxial growth along the conductive axes is a strategy to overcome slow electron transport and low photocurrent densities in layered materials such as Bi2WO6.
Mesa CA, Steier L, Moss B, et al., 2020, Impact of synthesis route on the water oxidation kinetics of hematite photoanodes, The Journal of Physical Chemistry Letters, Vol: 11, Pages: 7285-7290, ISSN: 1948-7185
Operando spectroelectrochemical analysis is used to determine the water oxidation reaction kinetics for hematite photoanodes prepared using four different synthetic procedures. Whilst these photoanodes exhibit very different current / voltage performance, their underlying water oxidation kinetics are found to be almost invariant. Higher temperature thermal annealing was found to correlate with a shift in the photocurrent onset potential towards less positive potentials, assigned to a suppression of both back electron-hole recombination and of charge accumulation in intraband-gap states, indicating these intraband-gap states do not contribute directly to water oxidation.
Achilleos DS, Yang W, Kasap H, et al., 2020, Solar Reforming of Biomass with Homogeneous Carbon Dots, ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 18184-18188, ISSN: 1433-7851
Windle CD, Wieczorek A, Xiong L, et al., 2020, Covalent grafting of molecular catalysts on C(3)N(x)H(y)as robust, efficient and well-defined photocatalysts for solar fuel synthesis, CHEMICAL SCIENCE, Vol: 11, Pages: 8425-8432, ISSN: 2041-6520
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