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Funding: J.L.P. thanks the University of St Andrews for funding and the Carnegie Trust for a Research Incentive Grant (RIG008653). The authors also thank EPSRC for funding (EP/T019298/1, EP/R023751/1 and EP/V034138/1). L.K.J. thanks UKRI for a Future Leaders Fellowship (MR/T022094/1). One of the great advantages of organic–inorganic metal halides is that their structures and properties are highly tuneable and this is important when optimizing materials for photovoltaics or other optoelectronic devices. One of the most common and effective ways of tuning the electronic structure is through anion substitution. Here, we report the inclusion of bromine into the layered perovskite [H3N(CH2)6NH3]PbBr4 to form [H3N(CH2)6NH3]PbBr4·Br2, which contains molecular bromine (Br2) intercalated between the layers of corner-sharing PbBr6 octahedra. Bromine intercalation in [H3N(CH2)6NH3]PbBr4·Br2 results in a decrease in the band gap of 0.85 eV and induces a structural transition from a Ruddlesden–Popper-like to Dion–Jacobson-like phase, while also changing the conformation of the amine. Electronic structure calculations show that Br2 intercalation is accompanied by the formation of a new band in the electronic structure and a significant decrease in the effective masses of around two orders of magnitude. This is backed up by our resistivity measurements that show that [H3N(CH2)6NH3]PbBr4·Br2 has a resistivity value of one order of magnitude lower than [H3N(CH2)6NH3]PbBr4, suggesting that bromine inclusion significantly increases the mobility and/or carrier concentration in the material. This work highlights the possibility of using molecular inclusion as an alternative tool to tune the electronic properties of layered organic–inorganic perovskites, while also being the first example of molecular bromine inclusion in a layered lead halide perovskite. By using a combination of crystallography and computation, we show that the key to this manipulation of the electronic structure is the formation of halogen bonds between the Br2 and Br in the [PbBr4]∞ layers, which is likely to have important effects in a range of organic–inorganic metal halides. Publisher PDF

Here we report the synthesis and properties of some lead-free organic bismuth halides. β-(PPD)2Bi2I10 has the longest average charge carrier lifetime (>1 μs) of the materials studied here, of the same order of magnitude as that of (CH3NH3)PbI3 and has a low band gap.

In this paper we demonstrate a novel optical receiver for visible light communications that combines a fluorescent antenna and a silicon photomultiplier (SiPM). The fluorescent antenna is configured in a slab geometry to collect and absorb an incoming optical data signal, and to waveguide the resulting fluorescence to an edge where it is detected by the SiPM. The antenna incorporates the fluorophore, pentafluorene, selected for its very high bandwidth of 245 MHz, high photoluminescence quantum yield of 90%, and emission spectrum that matches the wavelengths most efficiently detected by the SiPM. The performance of a receiver, comprising the fluorescent antenna and a J-series 30020 SiPM manufactured by ON Semiconductor, was assessed in a 30 cm data link with a 405 nm GaN laser diode transmitter, both in the dark and under 500 lux of ambient white light. The fluorescent antenna successfully rejects ambient light by a factor of 20, limited by extrinsic scattering in the thin film. Using on-off-keying with decision feedback equalization, a maximum data rate of 1.4 Gbps was demonstrated in 500 lux of ambient light. Using the pentafluorene antenna plus a BG3 filter, provides a 200 fold suppression of ambient light, and can increase the data rate of the receiver at low signal powers by up to a factor of 2. When operating in ambient light the composite receiver requires only 2.5 times more signal power than when it operates in the dark, with this power penalty reducing to a factor of 1.2 at 1 Gbps.

Funding: LKJ acknowledges funding from UKRI-FLF through MR/T022094/1. LKJ also acknowledges, Professor Iain Baikie for assistance with the work function and APS measurements, and Professor Phil King and Gordon Kentish, School of Physics and Astronomy, University of St Andrews for the XRD measurements and would like to acknowledge (EPSRC): EP/T023449/1. This research used resources of the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. Work was performed at beamline 12.3.2, beamline scientist Nobumichi Tamura. M. A. acknowledges support by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231 (D2S2 program KCD2S2). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. IDWS acknowledges funding from EPSRC through EP/l017008/1. Indoor photovoltaics are receiving tremendous attention due to the continuous development of the Internet of Things. The present study reports how the fast processing of the triple halide perovskite enables the retention of chlorine and the beneficial role of chlorine in enhancing the indoor light harvesting of a wide bandgap triple anion (TA) perovskite CH3NH3PbI2.6Br0.2Cl0.2. The kinetics of chlorine incorporation/escape investigated by in situ grazing incidence wide-angle X-ray scattering revealed the escape of chlorine after the first ten minutes of thermal annealing and the findings were corroborated with elemental analysis by wavelength dispersive X-ray spectroscopy. The best-performing TA perovskite indoor-photovoltaic device achieved a steady-state power conversion efficiency (PCE) of 25.1% with an output power density of ∼75 μW cm−2 under 1000 lux indoor illumination (0.3 mW cm−2 irradiance). Improved crystalline quality, reduced density of trap states and longer carrier lifetime were achieved by the triple anion alloying method. The detrimental role of the commonly used hole transporting layer (HTL) of Spiro-MeOTAD under indoor lighting conditions leading to J–V hysteresis was also investigated, which could then be effectively suppressed by replacing Spiro-MeOTAD with undoped P3HT. The optimized TA perovskite indoor PV cells were then successfully used to wirelessly power a textile fiber-based temperature sensor. The results from the present study demonstrate a novel route to incorporate chlorine effectively and maximize the steady state power output from halide perovskite indoor photovoltaic devices and their promising potential for the IoT industry. Publisher PDF

AKG is grateful to the Royal Society for Newton International Fellowship NF171163. We acknowledge support from the Engineering and Physical Sciences Research Council of the UK (grants EP/P010482/1 and EP/L017008/1). We are also grateful for financial support from the University of St Andrews Restarting Research and Restarting Interdisciplinary Research Funding Schemes (SARRF and SARIRF) which are funded through the Scottish Funding Council grant reference SFC/AN/08/020. We have designed a highly twisted small TADF emitter PXZ-α-DK based on an a-diketone (α-DK) as a strong acceptor and phenoxazine (PXZ) as a strong donor to obtain red-shifted emission in comparison to the equivalent a-diketone linked to 9,9-dimethyl-9,10-dihydroacridine (DMAC). The PXZ-α-DK shows emission at 586 nm and DMAC-α-DK shows emission at 548 nm in 1,3-bis(N-carbazolyl)benzene (mCP) host at 1.5 wt% doping of the emitter, with short-delayed lifetimes of 6.9 μs for PXZ-α-DK and 7.6 μs for DMAC-α-DK. OLEDs fabricated using these emitters show green electroluminescence at 555 nm for DMAC-α-DK, with a maximum external quantum efficiency, EQEmax, of 6.3%, and orange electroluminescence at 585 nm for PXZ-α-DK, with an EQEmax of 0.8%. We corroborate the optoelectronic properties of these emitters with DFT calculations. Postprint

Funding: This work was financially supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant (agreement no. 764837) and NCN Opus grant no. 2019/35/B/ST4/03280. We are also grateful to the Engineering and Physical Sciences Research Council of the UK for financial support from grants EP/R511778/1 and EP/L015110/1. Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future. Publisher PDF

Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No 838885 (NarrowbandSSL). S.M.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship (grant agreement No 838885 NarrowbandSSL). We would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. E.Z-C. and I.D.W.S acknowledge support from EPSRC (EP/L017008, EP/P010482/1). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F. R. S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). G. R. acknowledges a grant from the ‘‘Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture’’ (FRIA) of the FRS-FNRS. We present a p- and n-doped nonacene compound, NOBNacene, that represents a rare example of a linearly extended ladder-type multiresonant thermally activated delayed fluorescence (MR-TADF) emitter. This compound shows efficient narrow deep blue emission, with a λPL of 410 nm, full width at half maximum, FWHM, of 38 nm, photoluminescence quantum yield, ΦPL of 71 %, and a delayed lifetime, τd of 1.18 ms in 1.5 wt % TSPO1 thin film. The organic light-emitting diode (OLED) using this compound as the emitter shows a comparable electroluminescence spectrum peaked at 409 nm (FWHM=37 nm) and a maximum external quantum efficiency (EQEmax) of 8.5 % at Commission Internationale de l’Éclairage (CIE) coordinates of (0.173, 0.055). The EQEmax values were increased to 11.2 % at 3 wt % doping of the emitter within the emissive layer of the device. At this concentration, the electroluminescence spectrum broadened slightly, leading to CIE coordinates of (0.176, 0.068). Publisher PDF

H.L. would like to thank the University of St. Andrews for financial support via a St. Leonard’s scholarship. The authors acknowledge facilities access made possible through support from the EPSRC Light Element Analysis facility Grant EP/T019298/1 and the EPSRC Strategic Equipment Resource Grant EP/R023751/1. Vacancy-ordered halide perovskites have received great interest in optoelectronic applications. In this work, we report the novel inorganic halide Cs10MnSb6Cl30 with a distinctive 10H (10-layer hexagonal) perovskite polytype structure with (hcccc)2 stacking. Cs10MnSb6Cl30 has 30% B-site vacancies ordered at both corner- and face-sharing sites, resulting in [MnSb6Cl30]10–n columns, i.e., a reduction of octahedral connectivity to 1D. This results in enhanced photoluminescence in comparison to the previously reported 25% vacancy-ordered 3C polytype Cs4MnSb2Cl12 with 2D connectivity. This demonstrates not only the existence of the 10H perovskite structure in halides but also demonstrates the degree of B-site deficiency and stacking sequence variation as a direction to tune the optical properties of perovskite polytypes via vacancy rearrangements. Publisher PDF

Funding: The St Andrews team is grateful to the Engineering and Physical Sciences Research Council (EPSRC) for support from grants EP/P010482/1, EP/R035164/1 and EP/L017008/1. Kyushu team would like to acknowledge Kyulux inc and JSPS Core-to-Core Program (grant number: JPJSCCA20180005) for the support of this project. Three new 1,2,4,5-tetraphenylimidazole derivatives, 9,9-dimethyl-10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-9,10-dihydroacridine ( DMAC - TPI ), 10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-10H-phenoxazine ( PXZ-TPI ), and 10-(4-(2,4,5-triphenyl-1H-imidazol-1-yl)phenyl)-10H-phenothiazine ( PTZ - TPI ), bearing different electron donors at the N1 position of the imidazole were synthesised and characterised. DMAC - TPI and PXZ - TPI showed narrow emission at λPL of 388 and 418 nm in toluene, and in doped films in Zeonex polymer (1 wt.%) at λPL 381 and 407 nm, respectively, with a full width at half maximum (FWHM) ranging 0.42-0.44 eV. DMAC - TPI and PXZ - TPI are predicted to show very low oscillator strength for the low-energy transitions, which aligns to the observed low photoluminescence quantum yields. Both molecules showed a singlet-triplet energy gap (ΔEST of around 1.2 eV) that is much too large to enable reverse intersystem crossing and thermally activated delayed fluorescence. Connecting a donor group to TPI at the N1 position can lead to room temperature phosphorescence (RTP), as the example of PTZ - TPI showed. Publisher PDF

Funding: S. W. thanks the China Scholarship Council (201906250199). A. K. G. is grateful to the Royal Society for Newton International Fellowship NF171163. EZ-C and IDWS acknowledge support from EPSRC (EP/L017008, EP/P010482/1). We are also grateful for financial support from the University of St Andrews Restarting Research Funding Scheme (SARRF) which is funded through the Scottish Funding Council grant reference SFC/AN/08/020. EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). We would also like to thank the Leverhulme Trust (RPG-2016-047) for financial support. Herein, we demonstrate how judicious selection of donor decorating a central multi-resonant thermally activated delayed fluorescence (MR-TADF) core based on DiKTa can lead to very high-performance OLEDs. Decorating the DiKTa core with triphenylamine (TPA) and diphenylamine (DPA), 3TPA-DiKTa and 3DPA-DiKTa exhibit bright, narrowband green and red emission in doped films, respectively. The OLEDs based on these emitters showed record-high performance with maximum external quantum efficiencies (EQEmax) for this family of emitters, with a EQEmax of 30.8% for 3TPA-DiKTa at λEL of 551 nm and 16.7% for 3DPA-DiKTa at λEL of 613 nm. The efficiency roll-off in the OLEDs was improved significantly by using 4CzIPN as an assistant dopant in hyperfluorescence (HF) devices. The outstanding device performance has been attributed to preferential horizontal orientation of the transition dipole moments of 3TPA-DiKTa and 3DPA-DiKTa. Publisher PDF

AKG is grateful to the Royal Society for Newton International Fellowship NF171163. We acknowledge support from the Engineering and Physical Sciences Research Council of the UK (grants EP/P010482/1 and EP/L017008/1). We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for analytical services. We thank Umicore for providing palladium (II) acetate. We report an organic emitter containing a β-triketone electron acceptor core and phenoxazine as the electron donors ( TPXZBM ) for solution-processed organic light-emitting diodes (OLEDs). The resulting molecule is very unusual because it shows both thermally activated delayed fluorescence (TADF) and intramolecular proton transfer. We compare its performance with the previously reported diketone analogue PXZPDO . Solution-processed OLEDs of PXZPDO and TPXZBM show maximum external quantum efficiencies of 20.1% and 12.7%, respectively. The results obtained for the solution-processed PXZPDO -based device are as good as the previously reported evaporated device. At a very high luminance of 10,000 cd/m2 the efficiency of the OLEDs was 10.6% for PXZPDO and 4.7% for TPXZBM , demonstrating relatively low efficiency roll-off for TADF materials. The low efficiency roll-off was rationalized on the basis of the short delayed lifetimes of 1.35 μs for PXZPDO and 1.44 μs for TPXZBM . Our results suggest that intramolecular proton transfer may be useful for the design of OLED materials with low efficiency roll-off. Postprint

GC acknowledges the EPSRC for funding (EP/E036244/1). JMS acknowledges the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 for PhD funding. JMS also acknowledges Dr Nor Basid Adiwibawa Prasetya for helpful advice. Dr L. K. Jagadamma acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (European Commission) (MCIF: No. 745776). Thiophene-based semiconductors are amongst the most successful materials in organic electronics. In this contribution, we present the synthesis and characterisation of two thiophene-based macrocycles as well as their evaluation in organic-electronic devices. McT-1 is composed of ten thiophene moieties, whereas in McT-2, four additional electron-deficient benzothiadiazole moieties are incorporated to form a donor–acceptor (D–A) π-system. Red-shifted and broadened absorption spectra as well as more positive redox potentials are observed in McT-2, whereas McT-1 displays a sharper absorption band with a higher extinction coefficient. Macrocycle McT-1 shows emission in the yellow region whereas McT-2 displays emission in the red wavelength region. DFT calculations predict the macrocycles to comprise of mainly the E,E isomers with a near-planar structure, which is further supported by the single crystal X-ray structure for McT-1. Their charge transporting properties are determined by fabricating thin-film OFETs. The photovoltaic properties of McT-1 and McT-2 are also investigated by fabricating bulk heterojunction (BHJ) devices and their potential as photodetectors has been evaluated. Publisher PDF

S.W. thanks the China Scholarship Council (201906250199). EZ-C and IDWS acknowledge support from EPSRC (EP/L017008, EP/P010482/1). We are also grateful for financial support from the University of St Andrews Restarting Research Funding Scheme (SARRF) which is funded through the Scottish Funding Council grant reference SFC/AN/08/020. EZ-C is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). We would also like to thank the Leverhulme Trust (RPG-2016-047) for financial support. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska Curie grant agreement No 838885 (NarrowbandSSL). S.M.S. acknowledges support from the Marie Skłodowska-Curie Individual Fellowship. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). D.B. is a FNRS Research Director. Strategies to tune the emission of multiresonant thermally activated delayed fluorescence (MR-TADF) emitters remain rare. Here, we explore the effect of donor substitution about a MR-TADF core on the emission energy and the nature of the excited state. We decorate different numbers and types of electron-donors about a central MR-TADF core, DiKTa. Depending on the identity and number of donor groups, the excited state either remains short-range charge transfer (SRCT) and thus characteristic of an MR-TADF emitter or becomes a long-range charge transfer (LRCT) that is typically observed in donor–acceptor TADF emitters. The impact is that in three examples that emit from a SRCT state, Cz-DiKTa, Cz-Ph-DiKTa, and 3Cz-DiKTa, the emission remains narrow, while in four examples that emit via a LRCT state, TMCz-DiKTa, DMAC-DiKTa, 3TMCz-DiKTa, and 3DMAC-DiKTa, the emission broadens significantly. Through this strategy, the organic light-emitting diodes fabricated with the three MR-TADF emitters show maximum electroluminescence emission wavelengths, λEL, of 511, 492, and 547 nm with moderate full width at half-maxima (fwhm) of 62, 61, and 54 nm, respectively. Importantly, each of these devices show high maximum external quantum efficiencies (EQEmax) of 24.4, 23.0, and 24.4%, which are among the highest reported with ketone-based MR-TADF emitters. OLEDs with D–A type emitters, DMAC-DiKTa and TMCz-DiKTa, also show high efficiencies, with EQEmax of 23.8 and 20.2%, but accompanied by broad emission at λEL of 549 and 527 nm, respectively. Notably, the DMAC-DiKTa-based OLED shows very small efficiency roll-off, and its EQE remains 18.5% at 1000 cd m–2. Therefore, this work demonstrates that manipulating the nature and numbers of donor groups decorating a central MR-TADF core is a promising strategy for both red-shifting the emission and improving the performance of the OLEDs. Publisher PDF

The authors are highly thankful for the financial support of Higher Education Commission (HEC) Pakistan through the equipment/research grants (6976/Federal/NRPU/R&D/HEC/2017), (20-3071/NRPU/R&D/HEC/13). Author ZS acknowledges HEC for indigenous PhD Fellowship Phase-II, Batch-II, 2013, PIN 213-66018-2PS2-127 and International Research Support Initiative Programme (IRSIP). Author LKJ acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (European Commission) (MCIF: No. 745776). This work demonstrates a route to making mixed halide perovskite powders at room temperature by the anti-solvent-assisted crystallization method. Although, mixed halide CH3NH3PbBr3−xClx perovskites have been prepared by different methods, however, to the best of our knowledge the anti-solvent-assisted crystallization method is employed here for the first time to prepare mixed halide CH3NH3PbBr3−xClx perovskite powders. Solution-processed methyl ammonium lead tribromide CH3NH3PbBr3 (x = 0) and different amounts of chloride (Cl) containing mixed halide perovskites (CH3NH3PbBr3−xClx) were prepared for compositions of x = 0.5, 1, 1.25, 1.75. It reveals that bulk CH3NH3PbBr3−xClx samples are highly crystalline and exists in pure single cubic phase with an increased tolerance factor as compared to pure CH3NH3PbBr3. The CH3NH3PbBr3 perovskite has space-group Pm-3 m and a cell parameter of 5.930 Å (volume = 206 Å). The synthesis route adopted here gives access to hybrid perovskites powders with high Cl content and hence enables the band gap to be precisely tuned over a range from 2.26 to 2.49 eV. The powder samples display the subtle shifts in the emission spectra and the photoluminescence kinetics exhibits a decrease in average lifetime by increasing the Cl contents due to the presence of trap states in the structures that encourage non-radiative recombination of charge carrier. Conventionally, the CH3NH3PbBr3-based inverted solar cell architecture is prepared via mixing of the CH3NH3Br and PbBr2 precursors. In contrast, herein, the precursor solutions are directly prepared from the CH3NH3PbBr3 powder and the active layer of the inverted perovskite solar cells are then spin coated using this solution. The high Voc value of the fabricated solar cells potentially makes it a promising candidate for tandem photovoltaic, photocatalytic water splitting, and semi-transparent photovoltaic applications. Postprint Postprint

Organic optoelectronic devices combine high-performance, simple fabrication and distinctive form factors. They are widely integrated in smart devices and wearables as flexible, high pixel density organic light emitting diode (OLED) displays, and may be scaled to large area by roll-to-roll printing for lightweight solar power systems. Exceptionally thin and flexible organic devices may enable future integrated bioelectronics and security features. However, as a result of their low charge mobility, these are generally thought to be slow devices with microsecond response times, thereby limiting their full scope of potential applications. By investigating the factors limiting their bandwidth and overcoming them, we demonstrate here exceptionally fast OLEDs with bandwidths in the hundreds of MHz range. This opens up a wide range of potential applications in spectroscopy, communications, sensing and optical ranging. As an illustration of this, we have demonstrated visible light communication using OLEDs with data rates exceeding 1 gigabit per second., Organic LEDs (OLEDs) have generally been considered to be slow devices. Through engineering the structure and materials of OLEDs, the authors achieve a breakthrough in the high-speed operation of OLEDs and demonstrate a 1 Gbps optical wireless link using the OLEDs.

Funding: We acknowledge support from the European Commission (European Research Council grant 321305) and Marie Sklodowska-Curie Individual Fellowship grant 745776. We are also grateful to EPSRC for support from grants (EP/L017008/1 and EP/L012294/1). We investigated singlet exciton diffusion in three ITIC derivatives used as electron acceptors in organic photovoltaics (OPVs) by time-resolved photoluminescence volume quenching and exciton–exciton annihilation. The exciton diffusion coefficient was found to be in the range of 0.003–0.007 cm2 s−1 which leads to a three-dimensional exciton diffusion length of up to 31 nm. We fabricated solar cells using bulk heterojunctions of these acceptors with the electron donor PTB7-Th which showed ∼7% efficiency and large scale phase separation. Our results show that long range exciton diffusion and large domains offer significant advantages for OPVs. Publisher PDF

Funding was provided by a Leverhulme Trust Research Project grant (no. RPG-2018-113) to H.L.B., G.A.T. and I.D.W.S., an Engineering and Physical Sciences Research Council grant (no. EP/L017008/1) to G.A.T. and I.D.W.S., and a São Paulo Research Foundation (FAPESP) individual grant (no. 2016/14017-0) to G.H.P.F. The euphotic-mesophotic transition is characterized by dramatic changes in environmental conditions, which can significantly alter the functioning of ecosystem engineers and the structure of their associated communities. However, the drivers of biodiversity change across the euphotic-mesophotic transition remain unclear. Here, we investigated the mechanisms affecting the biodiversity-supporting potential of free-living red coralline algae-globally important habitat creators-towards mesophotic depths. Across a 73 m depth gradient, we observed a general decline in macrofaunal biodiversity (fauna abundance, taxon richness and alpha diversity), but an increase in beta-diversity (i.e. variation between assemblages) at the deepest site (86 m depth, where light levels were less than 1% surface irradiance). We identified a gradient in abundance decline rather than distinct ecological shifts, driven by a complex interaction between declining light availability, declining size of the coralline algal host individuals and a changing host taxonomy. However, despite abundance declines, high between-assemblage variability at deeper depths allowed biodiversity-supporting potential to be maintained, highlighting their importance as coastal refugia. Postprint

The distance that excitons can travel is a key parameter for organic photovoltaic materials. In the August issue of Science Advances, Sneyd and colleagues report a breakthrough in increasing exciton diffusion length to 300 nm by using highly ordered nanofibers. This approach can enable simpler and more stable solar cells. Postprint

Immunodiagnostics have been widely used in the detection of disease biomarkers. The conventional immunological tests in central laboratories require expensive equipment and, for non-specialists, the tests are technically demanding and time-consuming, which has prevented their use by the public. Thus, point-of-care tests (POCT), such as lateral flow immunoassays, are being, or have been, developed as more convenient and low-cost methods for immunodiagnostics. However, the sensitivity of such tests is often a concern. Here, a fluorescence-linked immunosorbent assay (FLISA) using organic light-emitting diodes (OLEDs) as excitation light sources was investigated as a way forward for the development of compact and sensitive POCTs. Phycoerythrin (PE) was selected as the fluorescent dye, and OLEDs were designed with different emission spectra. The leak-age light of different OLEDs for exciting PE was then investigated to reduce the background noise and improve the sensitivity of the system. Finally, as proof of principle that OLED-based technology can be successfully further developed for POCT, antibody to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in human serum was detected by OLED-FLISA. Publisher PDF

E.Z.-C. thanks the Leverhulme Trust (No. RPG-2016-047) and the University of St Andrews for support. The authors are grateful to the EPSRC for financial support (grants EP/ P007805/1, EP/P010482/1, EP/L017008/1, EP/J01771X, and EP/J00916). M.M. thanks the Innovation Programme H2020-MSCA-IF-2014-659237 for financial support. W.L. thanks the China Scholarship Council (grant number 201708060003). V.L. thanks the F.R.S.-FNRS for his Research Associate position. Computational resources have been provided by the Consortium des É quipements de Calcul Intensif (CÉ CI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.FNRS) under Grant No. 2.5020.11, GEQ U.G006.15, 1610468, and RW/GEQ. (2016). D.B. is an FNRS Research Director. Herein, we report the use of spiro-configured fluorene-xanthene scaffolds as a novel, promising, and effective strategy in thermally activated delayed fluorescence (TADF) emitter design to attain high photoluminescence quantum yields (ΦPL), short delayed luminescence lifetime, high external quantum efficiency (EQE), and minimum efficiency roll-off characteristics in organic light-emitting diodes (OLEDs). The optoelectronic and electroluminescence properties of SFX (spiro-(fluorene-9,9′-xanthene))-based emitters (SFX-PO-DPA, SFX-PO-DPA-Me, and SFX-PO-DPA-OMe) were investigated both theoretically and experimentally. All three emitters exhibited sky blue to green emission enabled by a Herzberg–Teller mechanism in the excited state. They possess short excited-state delayed lifetimes (

Research at Kyushu, Kyoto and St Andrews Universities was supported by EPSRC and JSPS Core to Core grants (JSPS Core-to-core Program; EPSRC grant number EP/R035164/1). Authors are also grateful for financial support from the Program for Building Regional Innovation Ecosystems of the Ministry of Education, Culture, Sports, Science and Technology, Japan, JST ERATO Grant JPMJER1305, JSPS KAKENHI JP20H05840, and Kyulux Inc. The photophysical analysis of thermally activated delayed fluorescence (TADF) materials has become instrumental to providing insight into their stability and performance, which is not only relevant for organic light-emitting diodes (OLED), but also for other applications such as sensing, imaging and photocatalysis. Thus, a deeper understanding of the photophysics underpinning the TADF mechanism is required to push materials design further. Previously reported analyses in the literature of the kinetics of the various processes occurring in a TADF material rely on several a priori assumptions to estimate the rate constants for forward and reverse intersystem crossing (ISC and RISC, respectively). In this report, we demonstrate a method to determine these rate constants using a three-state model together with a steady-state approximation and, importantly, no additional assumptions. Further, we derive the exact rate equations, greatly facilitating a comparison of the TADF properties of structurally diverse emitters and providing a comprehensive understanding of the photophysics of these systems. Postprint Postprint

AKG is grateful to the Royal Society for Newton International Fellowship NF171163. We acknowledge support from the Engineering and Physical Sciences Research Council of the UK (grants EP/P010482/1 and EP/L017008/1). The German Research Foundation (formally Deutsche Forschungsgemeinschaft DFG) in the framework of SFB1176 Cooperative Research Centre “Molecular Structuring of Soft Matter” (CRC1176, A4, B3, C2, C6) and the cluster 3D Matter made to order all funded under Germany's Excellence Strategy 2082/1-390761711 are acknowledged for financial contributions. We report two blue-emitting thermally activated delayed fluorescence (TADF) compounds employing a substituted carbazolophane (Czp) donor (indolo[2.2]paracyclophane). The compounds CNCzpPhTRZ and CF3CzpPhTRZ show emission maxima of 426 nm and 432 nm, respectively, with high photoluminescence quantum yields (ΦPL) of 73% and 80%, respectively. The singlet–triplet energy gap (ΔEST) of both emitters is 0.22 eV, resulting in long-delayed lifetimes of 132 μs for CNCzpPhTRZ and 158 μs for CF3CzpPhTRZ in PPT as the host matrix. Blue organic light-emitting diodes (OLEDs) showed maximum external quantum efficiencies (EQEs) of 7.4% for CNCzpPhTRZ and 11.6% for CF3CzpPhTRZ with electroluminescence maxima of ca. 460 nm. Publisher PDF

OLEDs have many attractive features as light sources for applications in biology and medicine. Photodynamic therapy (PDT) involves the use of light, a photosensitizer and oxygen to kill target cells which can be cancer, bacteria, parasites or fungi. There is a growing realisation that PDT may not only be useful for treating cancers, but also for the growing problem of antimicrobial resistance. This talk will describe the development of OLEDs for PDT, taking account of the particular needs of this application in terms of size, wavelength, light output, uniformity and lifetime. It will show work towards achieving high uniformity at high light output (~10 mW/cm2) over a substantial area and examples of antimicrobial applications.

A data rate of 363-Mb/s is achieved in a multiple-input-multiple-output experiment using 4 organic photovoltaics as receivers. The same system simultaneously extracted 10.9-mW. The resulting system model predicts 133-Gb/s using a 1000-cell organic solar panel. © 2021 The Author(s)