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We discuss the electronic and optical properties of semiconducting nanoparticles in the quantum-confinement regime and how they can be modeled accurately using first-principles calculations. We address how band-like features emerge from finite electronic states with increasing particle size and how we can control the characteristics of the electronic band structure by means of surface chemistry and alloying. In particular, we are focusing on technological important issues such as bandgap engineering of both magnitude of the bandgap as well as transition type (indirect vs. direct bandgap) and process stability of nanoparticles. We discuss this for several type of semiconducting nano particles composed of environmentally friendly materials, namely we discuss: (i) the origin of the experimentally observed change of the bandgap silicon (Si) nanoparticles upon functionalization with OH groups. We show that the decisive factor here is not as previously proposed surface-strain but charge transfer from the OH groups to the surface electronic states of the particle. (ii) How surface states control the optical properties of silicon carbide (SiC) nano particles, which can lead to in terms of quantum-confinement counter intuitive level diagrams We correlate the frontier electronic states to the measured absolute positions of the conductance band minimum and valance band maximum. (iii) Transition from indirect to direct bandgaps in ultrasmall tin (Sn) and alloyed silicon-tin (SixSn1-x) nanoparticles. Ultrasmall tin nanoparticles are found to have indeed a direct bandgap as recent measurements have proposed but its comparable small bandgap make applications difficult. We show that also for high enough Sn concentration binary silicon-ton alloyed nanoparticles can change their bandgap characteristic from indirect to direct, however the required tin concentration is larger than what one would expect from what is know for bulk silicon-tin. (iv) Lastly, we also investigate the thermal stability of silicon and tin nanoparticles which is especially important for high temperature processing necessary for in cooperating the nanoparticles into existing silicon technologies such as photovoltaic devices. We show that depending on the nanoparticles crystal structure they can remain stable up to several hundred degrees Celsius.

BACKGROUND COVID-19 data have been generated across the UK as a by-product of clinical care and public health provision, and numerous bespoke and repurposed research endeavours. Analysis of these data has underpinned the UK’s response to the pandemic and informed public health policies and clinical guidelines. However, these data are held by different organisations and this fragmented landscape has presented challenges for public health agencies and researchers as they struggle to find, navigate permissions to access and interrogate the data they need to inform the pandemic response at pace. OBJECTIVE To transform UK COVID-19 diagnostic datasets to be Findable, Accessible, Interoperable and Reusable (FAIR). METHODS A federated infrastructure model was rapidly built to enable the automated and reproducible mapping of health Data Partners’ pseudonymised data to the OMOP common data model without the need for any data to leave the data controllers’ secure environments and to support federated cohort discovery queries and meta-analysis. RESULTS 56 datasets from 19 organisations are being connected to the federated network. The data includes research cohorts and COVID-19 data collected through routine health care provision linked to longitudinal healthcare records and demographics. The infrastructure is live, supporting aggregate level querying of data across the UK. CONCLUSIONS CO-CONNECT was developed by a multidisciplinary team enabling rapid COVID-19 data discovery, instantaneous meta-analysis across data sources, and is researching streamlined data extraction for egress into a Trusted Research Environment (TRE) for research and public health analysis. CO-CONNECT has the potential to make UK health data more interconnected and better able to answer national-level research questions whilst maintaining patient confidentiality and local governance procedures. CLINICALTRIAL

Human attention is biased by several motivational factors. For instance, threat attracts attention. People also preferentially pay attention to goal-relevant stimuli even when they are not emotional. How is attention allocated when individuals encounter multiple stimuli with different motivational salience that compete for limited attentional resources? Recent evidence suggests that neutral but goal-relevant stimuli are prioritized over threat when they are simultaneously presented. However, the role of strategic attentional processes in this bias is unknown. To address this issue, we conducted two studies that presented goal-relevant and fear-conditioned threatening stimuli in a dot probe paradigm at early (30 ms) and later stages (250 ms) of attentional processing. Across both studies, attention was allocated to goal-relevant stimuli over threatening stimuli at both presentation times. However, attentional bias to goal-relevant stimuli was larger at later stages of attentional processing. Further, attention to goals over threat was reduced in people high in trait anxiety in the main study. These findings corroborate the conclusion that temporary goals determine attention allocation in a relatively automatic manner, but the influence of goals is stronger at later stages of attention allocation.

This work was supported by EPSRC (EP/K022237/1, EP/M024938/1 and EP/R023638/1), the EPSRC Supergen SuperSolar Hub, the Department for Employment and Learning (DEL) of Northern Ireland Studentship, and by the New Energy and Industrial Technology Development Organization (NEDO). We observe the extraction of carriers excited between two types of bands in the perovskite oxide, Sr-deficient strontium niobate (Sr0.9NbO3). Sr0.9NbO3 exhibits metallic behaviour and high conductivity, whilst also displaying broad absorption across the ultraviolet, visible, and near-infrared spectral regions, making it an attractive material for solar energy conversion. Furthermore, the optoelectronic properties of strontium niobate can easily be tuned by varying the Sr fraction or through doping. Sr-deficient strontium niobate exhibits a split conduction band, which enables two types of optical transitions: intraband and interband. However, whether such carriers can be extracted from an unusual material as such remains unproven. In this report, we have overcome the immense challenge of photocarrier extraction by fabricating an extremely thin absorber layer of Sr0.9NbO3 nanoparticles. These findings open up great opportunities to harvest a very broad solar spectral absorption range with reduced recombination losses. Publisher PDF

Silicon nanocrystals (Si-ncs) are fascinating candidates for numerous applications such as photovoltaic cells. Solar cell technologies are highly dependent on silicon materials and Si-ncs with optimal energy band gap present potential for further development high efficiency solar cells. Especially, the tunability of the Si energy bandgap by precisely controlling the size of Si-ncs due to quantum confinement effects is expected to increase the efficiency of third generation all silicon tandem solar cells. Among the different semiconductor nanocrystals, Si-ncs have a special value as they are generally non-toxic and have been widely used on an industrial scale. A crucial aspect for Si-ncs integration into PV devices is represented by the control of the surface characteristics. Since quantum confinement effects are observed for small nanocrystal sizes ( Another important issue is the doping of the Si-ncs. A number of issues especially regarding the large impurity formation energy by doping and transport are still in controversial debate. Doping of quantum confined Si-ncs offers unique opportunities to control the bandgap and the Fermi energy level. Particularly, boron-doped and phosphorus-doped quantum confined silicon nanocrystals (Si-ncs) are surface-engineered in colloidal solution by an atmospheric pressure radio frequency microplasma a will be underlined in this talk. In particular, we have performed the surface engineering of electrochemically etched p- and n-type Si-ncs where the no-change position of the dopant in Si-ncs is assured by room temperature processing [3]. We report on how the microplasma induced surface engineering can lead to drastically different outcomes due to different doping and how this impacts the corresponding optical and transport properties [3]. Next we report on Fermi level for doped Si-ncs. Our measurements demonstrate that surface engineering can tune the band energy levels and in particular the Fermi level. Indeed, we fabricate solar cells to test p-/n-type Si-ncs and induced surface chemistry to demonstrate the resulting effects. In particular it is noted that band alignment, dissociation efficiency and transport are all directly affected by the interplay of varying surface chemistry and doping levels. We demonstrate that surface chemistries induced on the Si-ncs strongly depend on the type of dopants and implications for third generation solar cells are discussed in details [4, 5]. As a final point, surfactant free microplasma surface-engineered Si-ncs can be integrated into the device architecture to be only optically active and provide a means of effective down-conversion of blue photons into red photons leading to 24% enhancement of the photocurrent under concentrated sunlight. We also show that the down-conversion effect under 1-sun is enhanced in the case of hybrid solar cells where microplasma engineered Si-ncs are also beneficial in the active absorption layer of the solar cells. References 1. V. Svrcek, T. Yamanari, D. Mariotti, K. Matsubara, M. Kondo, Enhancement of hybrid solar cell performance by polythieno [3,4-b]thiophenebenzodithiophene and microplasma-induced surface engineering of silicon nanocrystals, Appl. Phys. Lett. 2012, 100, 223904. 2. S. Mitra, V. Svrcek, D. Mariotti, K. Matsubara, M. Kondo, Microplasma-induced liquid chemistry as a tool for stabilization of silicon nanocrystals optical properties in water, Plasma Processes and Polym., 2014, 11 158. 3. T. Velusamy, S. Mitra, M.l Macias-Montero, V. Svrcek, D. Mariotti, Varying Surface Chemistries for p-Doped and n-Doped Silicon Nanocrystals and Impact on Photovoltaic Devices. ACS Appl Mater Interfaces, 2015, 7(51), 28207-14. 4. V. Svrcek, T. Yamanari, D. Mariotti, S. Mitra, T. Velusamy, K. Matsubara, A silicon nanocrystal/polymer nanocomposite as a down-conversion layer in organic and hybrid solar cells, Nanoscale, 2015, 7, 11566. 5. D. Mariotti, T. Belmonte, J. Benedikt, T. Velusamy, G. Jain, V. Svrcek, Low-Temperature Atmospheric Pressure Plasma Processes for ‘‘Green’’ Third Generation Photovoltaics, Plasma Process. Polym. 2016, 13, 70.

Over the past decade, lead halide perovskites have emerged as one of the leading photovoltaic materials due to their long carrier lifetimes, high absorption coefficients, high tolerance to defects, and facile processing methods. With a bandgap of ~1.6 eV, lead halide perovskite solar cells have achieved power conversion efficiencies in excess of 25%. Despite this, poor material stability along with lead contamination remains a significant barrier to commercialization. Recently, low-dimensional perovskites, where at least one of the structural dimensions is measured on the nanoscale, have demonstrated significantly higher stabilities, and although their power conversion efficiencies are slightly lower, these materials also open up the possibility of quantum-confinement effects such as carrier multiplication. Furthermore, both bulk perovskites and low-dimensional perovskites have been demonstrated to form hybrids with silicon nanocrystals, where numerous device architectures can be exploited to improve efficiency. In this review, we provide an overview of perovskite solar cells, and report the current progress in nanoscale perovskites, such as low-dimensional perovskites, perovskite quantum dots, and perovskite-nanocrystal hybrid solar cells.

We report highly stable zero-dimensional (CH3NH3)3Bi2I9 photovoltaic cells which demonstrate a 33% increase in performance after 2 years when hybridized with silicon nanocrystals (SiNCs). The natural oxidation of SiNCs is expected to consume radical species and improve the SiNC/(CH3NH3)3Bi2I9 interface and electronic coupling whilst also inhibiting defect-induced degradation.

Silicon’s (Si) indirect bandgap limits its absorption and possible applications, and therefore remarkable efforts are put into the possibility of fabricating a material compatible with the existing silicon technology that is also a direct bandgap material. Tin (Sn) alloying with silicon represents an exciting possibility to tune Si properties. In addition, at the quantum confinement size (

Herein, we demonstrate the customized, environmentally friendly tailoring of nanoparticles and their surface chemistry by short pulsed laser irradiation in liquids. This process allows for the formation of crystalline spherical particles exceeding several hundreds of nanometers in water from colloids of electrochemically etched silicon nanocrystals (Si-NCs), which exhibit quantum confinement effects and room-temperature stable luminescence. In particular, nanosecond (ns) pulsed laser irradiation of the Si-NC/water colloids causes the selective heating of the Si-NCs accompanied by the formation of spherical particles. In contrast, femtosecond (fs) laser pulsed irradiation induces the formation of colloidal Si-NCs with peculiar surface chemistry; in particular, fs pulses generate short-lived plasmas with more ionized species in water, which enable the surface engineering of quantum confined Si-NCs, thus limiting Si-NC agglomeration and enhancing their photoluminescent properties.

We acknowledge support by the Engineering and Physical Sciences Research Council (grant codes EP/M506631/1, EP/K015540/01, EP/K022237/1 and EP/M025330/1). IDWS and JTSI acknowledge Royal Society Wolfson research merit awards. Since first being used in a solar cell, the efficiencies of organic-inorganic tri-halide perovskite solar cells have rapidly increased. Although one possible mechanism for the hysteresis exhibited by these solar cells is ionic migration, the creation of vacancies in organic-inorganic tri-halide perovskites remains unexplored experimentally. Here, we have synthesised a range of samples, with the formula (CH3NH3)1-2x(H3NC2H4NH3)xPbI3, with different levels of ethylenediammonium doping to probe non-stoichiometry at the A-site of the perovskite. A region of solid solution was identified and this results in a change in photophysical properties. The influence of doping with ethylenediammonium iodide results in a decrease in HOMO level from 5.31 eV for x = 0 to -5.88 eV for x = 0.15. Postprint

We present the material methylammonium iodo bismuthate (MABI) with the chemical formula (CH 3 NH 3 ) 3 Bi 2 I 9 for application as the active layer in a photovoltaic cell. MABI adopts a perovskite-like structure and in recent years has attracted attention as a potential lead-free alternative to the typical leadhalide perovskites, or for use as the top cell in a tandem device. We demonstrate that MABI devices can be produced in open-air conditions and with good stability, without hysteresis, and can retain almost 60% of the initial PCE over a period of nearly 2 years without encapsulation. These devices can also favorably accommodate silicon nanocrystals and exhibit an increase in photocurrent, indicating opportunities to form various MABInanocrystal hybrid devices.

Organometal trihalide perovskite solar cells have attracted monumental attention in recent years. Today's best devices, based on a three-dimensional perovskite structure of corner-sharing PbI