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  • Journal article
    Kyeong M, Lee J, Daboczi M, Stewart K, Yao H, Cha H, Luke J, Lee K, Durrant JR, Kim J-S, Hong Set 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
    • Cite
    • Citations: 32
  • Journal article
    Francas L, Selim S, Corby S, Lee D, Mesa CA, Pastor E, Choi K-S, Durrant JRet al., 2021,

    Water oxidation kinetics of nanoporous BiVO<sub>4</sub> photoanodes functionalised with nickel/iron oxyhydroxide electrocatalysts

    , CHEMICAL SCIENCE, Vol: 12, Pages: 7442-7452, ISSN: 2041-6520
    • Cite
    • Citations: 45
  • Journal article
    Bucci A, Garcia-Tecedor M, Corby S, Rao RR, Martin-Diaconescu V, Oropeza FE, de la Pena O'Shea VA, Durrant JR, Gimenez S, Lloret-Fillol Jet 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
    • Cite
    • Citations: 29
  • Journal article
    Adler C, Selim S, Krivtsov I, Li C, Mitoraj D, Dietzek B, Durrant JR, Beranek Ret al., 2021,

    Photodoping and Fast Charge Extraction in Ionic Carbon Nitride Photoanodes

    <jats:p>&lt;p&gt;Ionic carbon nitrides based on poly(heptazineimides) (PHI) represent a vigorously studied class of materials with possibleapplications in photocatalysis and energy storage. Herein, we study, for thefirst time, the photogenerated charge dynamics in highly stable and binder-freePHI photoanodes using &lt;i&gt;in operando&lt;/i&gt; transientphotocurrents and spectroelectrochemical photoinduced absorption measurements.We discover that light-induced accumulation of long-lived trapped electronswithin the PHI film leads to effective photodoping of the PHI film, resultingin a significant improvement of photocurrent response due to more efficientelectron transport. Whilephotodoping has been previously reported for various semiconductors,it has never been shown before for carbon nitride materials. Furthermore, we find that the extraction kinetics ofuntrapped electrons are remarkably fast in these PHI photoanodes, with electronextraction times (ms) comparableto those measured for commonly employed metal oxide semiconductors. These results shed lighton the excellent performance of PHI photoanodes in alcohol photoreforming,including very negative photocurrent onset, outstanding fill factor, and thepossibility to operate under zero-bias conditions. More generally, the herereported photodoping effect and fast electron extraction in PHI photoanodes establisha strong rationale for the use of PHI films in various applications, such asbias-free photoelectrochemistry or photobatteries.&lt;br&gt;&lt;/p&gt;</jats:p>
  • Journal article
    Adler C, Selim S, Krivtsov I, Li C, Mitoraj D, Dietzek B, Durrant JR, Beranek Ret al., 2021,

    Photodoping and Fast Charge Extraction in Ionic Carbon Nitride Photoanodes
  • Journal article
    Dong Y, Cha H, Bristow H, Lee J, Kumar A, McCulloch I, Bakulin A, Durrant Jet al., 2021,

    Correlating charge-transfer state lifetimes with material ener-getics in polymer:non-fullerene acceptor organic solar cells

    , Journal of the American Chemical Society, Vol: 143, Pages: 7599-7603, ISSN: 0002-7863

    Minimizing the energy offset between the lowest exciton and charge-transfer (CT) states is a widely employed strategy to suppress the energy loss (Eg/q – VOC) in polymer:non-fullerene acceptor (NFA) organic solar cells (OSCs). In this work, transient absorption spectroscopy is employed to determine CT state lifetimes in a series of low energy loss polymer:NFA blends. The CT state lifetime is observed to show an inverse energy gap law dependence and decreases as the energy loss is reduced. This behavior is assigned to increased mixing/hybridization between these CT states and shorter-lived singlet excitons of the lower gap component as the energy offset ΔECT-S1 is reduced. This study highlights how achieving longer exciton and CT state lifetimes has the potential for further enhancement of OSC efficiencies.
  • Journal article
    Adler C, Selim S, Krivtsov I, Li C, Mitoraj D, Dietzek B, Durrant JR, Beranek Ret al., 2021,

    Photodoping and Fast Charge Extraction in Ionic Carbon Nitride Photoanodes
  • Journal article
    Moss B, Wang Q, Butler K, Grau-Crespo R, Selim S, Regoutz A, Hisatomi T, Godin R, Payne D, Kafizas A, Domen K, Steier L, Durrant Jet 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.
  • Journal article
    Mohapatra AA, Dong Y, Boregowda P, Mohanty A, Sadhanala A, Jiao X, Narayan A, McNeill CR, Durrant JR, Patil Set 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.
  • Journal article
    Chang Y-H, Carron R, Ochoa M, Bozal-Ginesta C, Tiwari AN, Durrant J, Steier Let 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.
  • Journal article
    Limbu S, Park K-B, Wu J, Cha H, Yun S, Lim S-J, Yan H, Luke J, Ryu G, Heo C-J, Kim S, Jin YW, Durrant JR, Kim J-Set 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
    • Cite
    • Citations: 17
  • Journal article
    Bozal-Ginesta C, Mesa CA, Eisenschmidt A, Francas L, Shankar RB, Anton-Garcia D, Warnan J, Willkomm J, Reynal A, Reisner E, Durrant JRet al., 2021,

    Charge accumulation kinetics in multi-redox molecular catalysts immobilised on TiO<sub>2</sub>

    , CHEMICAL SCIENCE, Vol: 12, Pages: 946-959, ISSN: 2041-6520
    • Cite
    • Citations: 10
  • Journal article
    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
    • Cite
    • Citations: 23
  • Journal article
    Wilson AA, Corby S, Francas L, Durrant JR, Kafizas Aet 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.
  • Journal article
    Sachs M, Cha H, Kosco J, Aitchison CM, Francas L, Corby S, Chiang C-L, Wilson AA, Godin R, Fahey-Williams A, Cooper AI, Sprick RS, McCulloch I, Durrant JRet 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
  • Journal article
    Mesa CA, Rao RR, Francas L, Corby S, Durrant JRet 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
    • Cite
    • Citations: 15
  • Journal article
    Francàs L, Selim S, Corby S, Lee D, Mesa C, Pastor E, Choi K-S, Durrant JRet al., 2020,

    Water Oxidation Kinetics of Nanoporous BiVO4 Photoanodes Functionalised with Nickel/iron Oxyhydroxide Electrocatalysts

    <jats:p>In this work, spectroelectrochemical techniques are employed to analyse the catalytic water oxidation performance of a series of three nickel/iron oxyhydroxide electrocatalysts deposited on FTO and BiVO&lt;sub&gt;4&lt;/sub&gt;, at neutral pH. Similar electrochemical water oxidation performance is observed for each of the FeOOH, Ni(Fe)OOH and FeOOHNiOOH electrocatalysts studied, which is found to result from a balance between degree of charge accumulation and rate of water oxidation. Once added onto BiVO4 photoanodes, a large enhancement in the water oxidation photoelectrochemical performance is observed in comparison to the un-modified BiVO&lt;sub&gt;4&lt;/sub&gt;. To understand the origin of this enhancement, the films were evaluated through time-resolved optical spectroscopic techniques, allowing comparisons between electrochemical and photoelectrochemical water oxidation. For all three catalysts, fast hole transfer from BiVO&lt;sub&gt;4&lt;/sub&gt; to the catalyst is observed in the transient absorption data. Using operando photoinduced absorption measurements, we find that water oxidation is driven by oxidised states within the catalyst layer, following hole transfer from BiVO&lt;sub&gt;4&lt;/sub&gt;. This charge transfer is correlated with a suppression of recombination losses which result in remarkably enhanced water oxidation performance relative to un-modified BiVO&lt;sub&gt;4&lt;/sub&gt;. Moreover, despite similar electrocatalytic performance of all three electrocatalysts, we show that variations in water oxidation performance observed among the BiVO&lt;sub&gt;4&lt;/sub&gt;/MOOH photoanodes stem from differences in photoelectrochemical and electrochemical charge accumulation in the catalyst layers. Under illumination, the amount of accumulated charge in the catalyst is driven by the injection of photogenerated holes from BiVO&lt;sub&gt;4&
  • Journal article
    Francàs L, Selim S, Corby S, Lee D, Mesa C, Pastor E, Choi K-S, Durrant JRet al., 2020,

    Water Oxidation Kinetics of Nanoporous BiVO4 Photoanodes Functionalised with Nickel/iron Oxyhydroxide Electrocatalysts
  • Journal article
    Nikolis VC, Dong Y, Kublitski J, Benduhn J, Zheng X, Huang C, Yuzer AC, Ince M, Spoltore D, Durrant JR, Bakulin AA, Vandewal Ket al., 2020,

    Field Effect versus Driving Force: Charge Generation in Small-Molecule Organic Solar Cells

    , ADVANCED ENERGY MATERIALS, ISSN: 1614-6832
  • Journal article
    Tian L, Tyburski R, Wen C, Sun R, Abdellah M, Huang J, DAmario L, Boschloo G, Hammarström L, Tian Het al., 2020,

    Understanding the Role of Surface States on Mesoporous NiO Films

    , Journal of the American Chemical Society, Vol: 142, Pages: 18668-18678, ISSN: 0002-7863
  • Journal article
    Achilleos DS, Yang W, Kasap H, Savateev A, Markushyna Y, Durrant JR, Reisner Eet al., 2020,

    Solar Reforming of Biomass with Homogeneous Carbon Dots

    , ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, Vol: 59, Pages: 18184-18188, ISSN: 1433-7851
    • Cite
    • Citations: 90
  • Journal article
    Corby S, Tecedor M-G, Tengeler S, Steinert C, Moss B, Mesa CA, Heiba HF, Wilson AA, Kaiser B, Jaegermann W, Francas L, Gimenez S, Durrant JRet al., 2020,

    Separating bulk and surface processes in NiO<sub><i>x</i></sub>electrocatalysts for water oxidation

    , SUSTAINABLE ENERGY & FUELS, Vol: 4, Pages: 5024-5030, ISSN: 2398-4902
    • Cite
    • Citations: 42
  • Journal article
    Dong Y, Nikolis VC, Talnack F, Chin Y-C, Benduhn J, Londi G, Kublitski J, Zheng X, Mannsfeld SCB, Spoltore D, Muccioli L, Li J, Blase X, Beljonne D, Kim J-S, Bakulin AA, D'Avino G, Durrant JR, Vandewal Ket 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.
  • Journal article
    Aitchison CM, Sachs M, Little MA, Wilbraham L, Brownbill NJ, Kane CM, Blanc F, Zwijnenburg MA, Durrant JR, Sprick RS, Cooper Aet 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
  • Journal article
    Moss B, Le H, Corby S, Morita K, Selim S, Sotelo-Vazquez C, Chen Y, Borthwick A, Wilson A, Blackman C, Durrant JR, Walsh A, Kafizas Aet 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.
  • Journal article
    Mesa CA, Steier L, Moss B, Francas L, Thorne JE, Grätzel M, Durrant JRet 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.
  • Journal article
    Hou B, Kim B-S, Lee HKH, Cho Y, Giraud P, Liu M, Zhang J, Davies ML, Durrant JR, Tsoi WC, Li Z, Dimitrov SD, Sohn JI, Cha S, Kim JMet al., 2020,

    Multiphoton Absorption Stimulated Metal Chalcogenide Quantum Dot Solar Cells under Ambient and Concentrated Irradiance

    , ADVANCED FUNCTIONAL MATERIALS, Vol: 30, ISSN: 1616-301X
  • Conference paper
    Maimaris M, Pettipher AJ, Walke DJ, Zheng X, Gorodetsky A, Shakya Tuladhar P, Crespo H, Tisch JWG, Bakulin Aet al., 2020,

    Tracking localised exciton formation in organic semiconductor material

    , Physical Chemistry of Semiconductor Materials and Interfaces IX, Publisher: SPIE, Pages: 11-11
  • Journal article
    Windle CD, Wieczorek A, Xiong L, Sachs M, Bozal-Ginesta C, Cha H, Cockcroft JK, Durrant J, Tang Jet al., 2020,

    Covalent grafting of molecular catalysts on C<sub>3</sub>N<sub><i>x</i></sub>H<sub><i>y</i></sub>as robust, efficient and well-defined photocatalysts for solar fuel synthesis

    , CHEMICAL SCIENCE, Vol: 11, Pages: 8425-8432, ISSN: 2041-6520
    • Cite
    • Citations: 16
  • Journal article
    Du T, Xu W, Xu S, Ratnasingham SR, Lin C-T, Kim J, Briscoe J, McLachlan MA, Durrant JRet al., 2020,

    Light-intensity and thickness dependent efficiency of planar perovskite solar cells: charge recombination versus extraction

    , Journal of Materials Chemistry C, Vol: 8, Pages: 12648-12655, ISSN: 2050-7526

    Photoactive layer thickness is a key parameter for optimization of photovoltaic power conversion efficiency (PCE), yet its impact on charge extraction and recombination hasn’t been fully understood in perovskite solar cells (PSCs). Herein we find that in planar PSCs the perovskite thickness yielding maximal PCE is strongly light-intensity dependent. Whilst under 1 sun irradiation the PCE is relatively invariant for perovskite thicknesses between 250 to 750 nm, at lower light intensities (0.1–0.5 sun) the thickest devices yield strongly enhanced PCE, but at higher light intensities (>1 sun) the thinnest devices give optimal PCE. Our results unravel that increased perovskite thickness leads to enhanced light absorption, reduced interfacial recombination at open circuit but greater bimolecular recombination losses at short circuit thus is suitable for devices working under weak illumination, typical of many real-world applications. Reducing perovskite thickness, however, shows the contrast trend and is suitable for PSCs working under concentrated illumination.

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