This presentation will provide an introduction to SPECIFIC Innovation and Knowledge Centre, Swansea University, UK; and the Active Building concept they have developed as a solution to support the transition to a low carbon built environment. Active Buildings support local and national electricity grid networks by integrating renewable energy technologies, energy storage and smart controls for heat, power and transport. SPECIFIC have designed and constructed several Active Building demonstrators in the UK and are now working with the SUNRISE team to design and construct an Active Building in the rural village of Khuded, India. There will be a brief overview of the UK Active Building examples, followed by an update on the design development and current status of the Khuded project.

Solar thermal collectors provide heated air by absorbing solar radiation. This heated air can then be used to supply heated air to a desalination or drying unit. The purpose of this work is to assess the air heating capacity of a glazed collector by assessing variables such as steel colour and coating type, glass coating type and configuration, and design parameters such as the air gap between the steel and the glass. A collector has been constructed from white acrylic and a solar rig has been used to simulate sunlight conditions. The results show a good negative correlation between the solar reflective index and the temperature uplift from ambient under solar radiation for the steel samples. However, there seems to be no clear correlation between the steel coating type and the temperature uplift from ambient. The glass tests show that the glass with a low-emissivity coating performs the best. However, when the glazed collector is constructed, the low-emissivity coating has a negative effect on the temperature uplift of the air and the steel, meaing that the uncoated glass has a higher temperature uplift for the air and the steel.

Technological advances in recent years have enabled incremental increases in the energy density of Li-ion batteries (LIBs), making them a cost-effective and practical option for applications that include transport and solar-power storage. LIBs are expected to continue to dominate the rechargeable battery market in the short term, with the global market worth a projected $94 billion by 2025. However, with energy density having plateaued in standard LIBs, new manufacturing solutions are needed to meet demand and keep pace with increasingly power-hungry applications by unlocking the commercial potential of other technologies. Furthermore, the sustainability and environmental costs of state-of-the-art LIBs are substantial barriers to a greener electrification of the economy. 

Rechargeable batteries that employ in-situ electroplating of Li or Na metal (also known as "anode free") will enable a substantial increase in energy density compared to current state-of-the-art LIBs (300 Wh/kg) and alleviate many of the issues on the environmental impact of production, recycling and disposal. In this presentation, recent advances in the design of  Na/Li "anode free" batteries will be discussed in terms of reduced mass, high energy densities, scalability and sustainability. The current collector and electrolyte's role in obtaining high Couloumbic efficiencies and increased cycle-life will be highlighted. Examples of systems in small and large formats will be shown to demonstrate the viability of the technologies and how they could enable a truly sustainable battery industry.

Focussing on energy storage for fixed applications such as grid support and off grid applications this talk will discuss some of the options for electrical energy storage and how we can ensure that we are developing technologies with the smallest environmental impact. 

Since there is environmental impact at all stages of the battery’s lifetime: materials use,  processing energy costs, battery use and end of life this talk will discuss how these different areas overlap and how focussing on one area can cause unintended consequences in the other areas.

Heavy industry, such as steel making, are UK CO₂ emissions hot spots and can release up to 50% of consumed energy as waste heat. The primary steel making at Tata Steel Port Talbot produces waste heat at a continuous 760MW, which is equivalent to the combined heating demand of around 500,000 homes and the capture and reuse of this heat would offset more than 1,000,000 tonnes of CO₂ annually.

The capture and reuse of waste heat is an essential component of the global decarbonisation plan, providing the opportunity to offset carbon produced during primary energy generation. Many production facilities already capture a large portion of medium and high grade waste heat but poor conversion efficiencies and high expense limit the capture of low grade heat. Focusing on low grade heat sources, the current work investigates the capture, storage and reutilisation of heat from industrial waste air streams using heat storage materials such as SIM (Salt In Matrix) and AGC (Alginate graphite composites).   

Ongoing site surveys and a review of previous waste heat projects are creating live energy maps of production facilities and have provided target temperatures to which heat capture materials can be attuned. The waste heat sources have been categorised between low, medium and high grade and ranked on feasibility of capture.    

Inhouse constructed, small-scale, reaction chambers allow the assessment of multiple charge and discharge cycles in an open-system configuration. These systems allow the replication of process conditions, without the need to infiltrate the process, providing a systematic and repeatable methodology for screening material sets. The data from these investigations can be subsequently analysed to determine the potential for energy capture across the production facility.    

Zwitterion cysteamine (2-aminoethanethiol) linker is employed for the first time to realize novel structural architectures of Hybrid Organic Inorganic lead perovskite framework and the applications of the same are also examined. In the solution based synthesis protocol a remarkable molecular diffusion-controlled crystal-to-crystal transformation of a perovskitoid structure to Ruddlesden-Popper phase (Red crystals, Pnma space group) is observed. The intermediate is stable and differs distinctly from all previous reports by way of a unique staggered arrangement of holes in the puckered 2D configuration with a face-sharing connection between the corrugated-1D double chains. This perovskitoid shows 5 orders of higher PL intensity along with an average lifetime of 143 ns as compared to the RP phase. 

We demonstrate the perovskitoid nanocrystals upon compositing with few layer black phosphorus behave as a selective Ni2+ ion (1.79 x 10-3 M concentration) detection PL On-Off-On probe along with the mechanism for detection. A significant recovery of the average lifetime of the nanocomposite is observed upon interaction with Ni2+ ions. A self powered photodetector is demonstrated using the perovskitoid phase crystallites. More than a factor of 10 change is seen in the current upon photoirradiation (light intensity,1.5 mW/cm2) at 0V. the photodetector showed good photostability for the measured duration of time.

This project will investigate the performance of different ultra-thin coatings in protecting the anode electrodes of battery coin cells against dendrite formation and parasitic side reactions with electrolytes. Current methods of Atomic Layer Deposition (ALD) have managed to successfully double the cycle life of Lithium metal anodes. This project will investigate an alternative method, Molecular Vapour Deposition (MVD). Unlike ALD, MVD is easily scalable and therefore highly likely to be commercialised by the battery manufacturing industry if successfully proven to work. This will require the investigation of various thin film materials (currently Al2O3, ZnO) and how their coating on anodes affects cycling performance of our test coin cells. Performance will be determined using sophisticated characterisation techniques such as Electrical Impedance Spectroscopy (EIS), Scanning Electron Microscopy (SEM) and X-Ray Spectroscopy (XPS)

This talk will present recent progress in the scale up of the triple mesoscopic carbon perovsktie solar cell from small laboratory scale devies (1cm2) to large area industrial scale fully interconnected modules (30 x 30cm2). The talk will cover three key elements in the process, the development and growth of device performance with material optimisation, the use of a low-toxicity factory-friendly solvent system and the methodology behind the fabrication route of the modules themselves. The talk will conclude with an overview of the challenges that remain in the next stage of the process in particular the handling and measuring of such large modules and their integration into an external array.

The current research envisages the use of microwave (MW) processed TiO₂ as an effective electron transport layer (ETL) for realizing improved performance in low temperature perovskite solar cell over the conventional perovskite solar cells with high-temperature processed ETL (~ 500 ^oC). This study proposes a new strategy to process defect-free compact TiO₂ layer at low temperature (~ 150 ^oC) in shorter time duration (1 minute) and is energy saving. Our low temperature solution-based processing protocol significantly improves optoelectronic and microstructural properties of TiO₂. Additionally, low-temperature processing route provides superior template for perovskite film growth leading to better ETL/perovskite interface with lower defects, improves perovskite film quality by increasing grain size and reduces strain in perovskite films subsequently resulting in enhanced V_oc, J_sc and Fill factor. These findings were extensively investigated by spectroscopic, structural and device characterization techniques followed by simulation studies. We envision that this facile, quick, low-temperature and energy saving approach of MW processing of TiO₂ is a promising technology which will be instrumental for commercialization of economical perovskite solar cells in near future. We also believe that this technique can lay the foundation for development of large-area flexible modules with single junction or multi-junction tandem architectures based on perovskite photovoltaic technology.

In this presentation, we will talk about the development of organic solar cells on opaque steel substrates. The challenges in fabricating a solar cell device on steel substrates are two fold: minimizing the substrate roughness so that smooth interfaces between various layers can be formed and maximizing the transmission of light from top of the device with an electrode as transparent as possible. In addition, for commercial realization prospects, processing should be as simple as possible and utilize low temperature steps. In our work, we have addressed these challanges by adopting various approaches related to substrate planarization, optimization of carrier selective layers and maximiation of the transparency of top electrodes. The best performing cells demonstrate power conversion efficiencies of ~6% using PTB7:PCBM blend as an active layer.

With the emergence of tandem solar cell structures, the role of transparent conductive oxide thin films implemented in these structures is gaining significant attention. Production and deposition of transparent conductive thin films requires precise deposition techniques when integrated within tandem cell structures and even more challenging when scalability is considered. Here we report on implementing deep artificial neural network models as a tool in predicting electrical property of transparent oxides deposited via sputtering technique based on the spectral emissions from the plasma. The end goal is to create smart sputter deposition systems dedicated to tandem solar cell manufacturing. 

This presentation focuses on advances of the research group in the development of materials and characterisation methods supporting the development of lead-halide perovskite solar cells. First, a new chemical route is presented for the fabrication of NiOx thin films at relatively low-T (270 C). Here, methylethanolamine is used as a complexing agent of Ni(OH)₂, enabling the dissolution of this compound in various solvents. The resulting precursors can be used to form thin NiOx films with good light transmission properties and are successfully implemented to the fabrication of inverted perovskite cells with comparable performance to that of cells prepared on standard NiOx films (approx. 10-11 %). Second, the presentation focuses on the application of T-controlled XRD to optimise the crystallization of various perovskite precursors. Finally, broad beam ion milling, a technique traditionally enabling the preparation of flat sample surfaces for EBSD analysis (crystal grain orientation in metals) is demonstrated as a novel approach for the preparation of neat cross-sections of C-based perovskite solar cells over a large range (1-2mm). This is used to better understand the complexity of structural variations across a single cell and potential defects affecting device performance.     

In this talk I will present recent work on understanding factors that influence long term stability and enhancing the open-circuit voltage of wide band gap perovskite solar cells

Resonance energy transfer (RET) can potentially improve device efficiencies of ternary blend organic solar cells (TBSCs). However, several parameters such as morphology of the blend, exciton lifetimes and charge separation driving forces influence the resulting excited state photophysics. Owing to this, spectroscopic studies on thin film of ternary blend have not unambiguously deconvolved the role of RET in observed enhancement of photocurrent densities, often downplaying the mechanistic aspects of RET associated enhancement. In this talk, I will discuss the role of resonance energy transfer in enhancing device efficiency by taking a few recent examples of ternary blend being persuaded in our laboratory.

Organic solar cells (OSCs) typically employ electron donor and acceptor materials to faciliate efficient charge generation from excitons. 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 – V_OC) in polymer:non-fullerene acceptor (NFA) OSCs. While a lot of studies have investigated the CT state energetics and its correlation with device photovoltage as well as voltage losses, the CT state dynamics still remains relatively unexplored. In my talk, I will discuss how transient absorption spectroscopy (TAS) is employed to determine CT state lifetimes in a series of low energy loss polymer:NFA blends. TAS measurements show that the CT state lifetime follows an inverse energy gap law dependence and decreases as the energy loss is reduced. This behavior is assigned to increased mixing between these CT states and shorter-lived singlet excitons of the lower gap component as the energy offset is reduced. These results highlight how achieving longer exciton and CT state lifetimes has the potential for further enhancement of OSC efficiencies.

Generation of energy using silicon solar cell is a well-established technology. However, silicon (like other semiconductors) fails to utilize the energy excess to its bandgap in the form of thermalization loss. To reduce these losses one of the solutions is to enhance sensitivity to light by sensitizing the silicon solar cell using singlet exciton fission. This singlet exciton fission in organic chromophore generates triplet excitons which needs to be transferred to silicon via an interlayer, which further should result in the creation of additional electron hole pairs and thus, boost the efficiency. However, the interlayer via which these triplets/triplet energy transfers play a crucial role. Thus, in our work we aim to study interlayers with different dielectric constant and its impact on the triplet transfer and device performance.

 In this talk we wiil give a bried overview on our research acitivies related to energy materials for optoelectronic device applications. Further the main focus will be on our recent findings of ultrafast triplets excitons in polymeric solids. Due to their potential for high-efficiency optoelectronic devices, the behavior of organic semiconductors has garnered increasing interest in recent years. Understanding the transport of excitons by diffusion of singlets and triplets is essential for developing efficient optoelectronic devices. Measuring the characteristically non-emissive triplets, however, continues to challenge the field. We have introduced a new experimental technique to measure exciton transport in the transverse direction of polymeric semiconductor thin-films. By using pulsed excitation to measured angle resolved delayed electroluminescence (ARDEL), the group’s method traces the position of the triplet exciton in the emissive layer of OLEDs. The triplet excitons are known to be very localized species in the organic polymers due to their parallel spin configuration and the mutual charge exchange between the molecules. The outcome of the work suggests that, in the case of well polymer chain packing, the triplet transport can be as good as the crystalline organic materials. The polyfluorene system exhibits an efficient triplet-triplet fusion process, which provides singlet excitons as delayed fluorescence and becomes a tool to study triplet exciton kinetics.

The results further characterize thin-film kinetics, which can lead to a better design of optoelectronic devices, like solar cells. Organic semiconductors uniquely exhibit singlet and triplet kinetics that share an important role in determining the performance of various optoelectronic devices. Results suggest the diffusion is significantly anisotropic in thinner films. As the thickness of the film increases, anisotropy reduces in triplet transport. Additionally, the group found that in thicker films, diffusivity approaches close to ultrahigh  10^-3 centimeters² per second, nearing that of similarly based crystalline organic thin films. These findings resolve the decade old mystery of unusually thick emissive layer based efficient OLEDs.

Near infrared (NIR) organic photodetectors (OPDs) have huge potential in many disciplines from communication and astronomy to biomedical sciences owing to their large-scale solution processability, wearability, flexibility, tunability and cost-effectiveness. However, successful realization of OPDs still face major challenges such as less photon harvesting, poor photoresponse beyond NIR wavelengths due to relatively high bandgap and uncertainty in measuring accurate detectivity estimation using current protocols.

Significant progress has been made to extend the spectral range by synthesizing organic materials with low bandgap, different donor-acceptor dopant combinations, dopant dyes or incorporating additional absorber and a multiplication layer.^1,2 However, these strategies compromise the achievable high EQE, low dark/noise current under bias and fast response time that are unfavourable for real-time photodetectors.

In light of challenges discussed above, this work focuses on tuning blend composition ratio in PM6:Y6 based bulk-heterojunction (BHJ) materials for building NIR sensitive fast organic photodiode. A photodiode vertical device architecture was fabricated where solution processing method was used to deposit the photoactive layer (PM6:Y6) sandwiched between ZnO (electron transport layer (ETL)) and MoO₃ (hole transport layer (HTL), as shown in the schematic above. We could achieve a maximum photoresponsivity of 0.54 A/W at 830 nm for the optimized PM6:Y6 photodetectors, which is among the highest for binary blend BHJ organic photodetectors till date. Moreover, optimization process is still going on in our laboratory to further improve the NIR photoresponse by reducing the dark current and noise levels in the photodetector system and tune the spectral response beyond 1000 nm.

References:

Z. Zhao, C. Xu, L. Niu, X. Zhang, and F. Zhang: Recent Progress on Broadband Organic Photodetectors and their Applications. Laser Photonics Rev. 14(11), 2000262 (2020).

Z. Wu, W. Yao, A. E. London, J. D. Azoulay, and T. N. Ng: Elucidating the Detectivity Limits in Shortwave Infrared Organic Photodiodes. Adv. Funct. Mater. 28(18), 1800391 (2018).

Mesoscopic carbon-based perovskite solar cells (CPSCs) are frequently described as a potential frontrunner for PSC commercialization. Previous work has introduced γ-valerolactone (GVL) as a sustainable, non-toxic, green alternative to GBL for CPSC perovskite precursors. In this work, methanol (MeOH) solvent additives are applied to enhance the performance and reproducibility of GVL-based precursors, through improving electrode wetting, infiltration, and perovskite crystal quality. Precursors incorporating 10% MeOH are found to enhance reproducibility and performance, achieving a champion PCE of 13.82% in a 1 cm² device and >9% in a 220 cm­² module fabricated in ambient conditions. Stability is also improved, with an unencapsulated MeOH device exhibiting a T80 of >420 hours at 50^oC in ambient humidity under AM1.5 illumination.

This work could make green GVL-based precursors more commercially attractive and provides an example of how green solvent engineering can be applied in the development, amelioration and scale-up of novel renewable technologies.

The energy bandgaps of Pb halide perovskites are higher than the optimal bandgap required for single junction solar cells, governed by the Shockley–Queisser (SQ) radiative limit. The pure Sn and Pb-Sn mixed based perovskites have drawn significant attention due to their ability to lead to lower bandgaps and opens a new door for all perovskite tandem application. There is continuous progress towards the rapid improvement in the power conversion efficiency of Sn and Pb-Sn mixed based PSCs. Along with efforts for efficiency, it is worth analysing the in-depth recombination dynamics for further development of Sn based PSCs. Lower bimolecular recombination rate constant (k) is often attributed for the high performance of PSCs. Herein, we study the role of ‘B’ cation in charge carrier recombination dynamics (CCRD) of ABX3 (A= MA+, FA+, Cs+; B = Pb2+, Sn2+ & X = I-) based PSCs. We fabricated p-i-n configuration based FA0.95Cs0.05PbI3 (pure Pb), MA0.20FA0.75Cs0.05SnI3 (pure Sn) and (MAPbI3)0.4 (FASnI3)0.6 (Pb–Sn mixed) PSCs and compare the CCRD of all the three PSCs. We optimized the Sn based perovskite thin film (pure Sn) in terms of moisture and thermal stability in order to minimize the error due to perovskite degradation. We note that despite having lower open-circuit voltage (VOC), pure Sn based PSC shows lower k than that of Pb-Sn mixed and pure Pb based PSCs, which is a contradictory result. This slow relaxation lifetime of the charge carrier in Sn based PSCs can be correlated to recombination through the defect states without introducing the quasi-Fermi-level splitting. Furthermore, our results suggest that the rate law of charge carrier decay has nonlinear dependence of k on n in Sn based PSCs, whereas it is linear in other two cases.

The high performance of hybrid perovskite-based devices is attributed to its excellent bulk-transport properties. However, carrier dynamics at the metal-perovskite interface and its influence on device operation are not widely understood. Here we explore the microscopic origins of the dominant transport mechanisms in methylammonium lead iodide (MAPbI₃) perovskite-based asymmetric metal-electrode lateral devices, with inter-electrode length varying from 4 μm to 120 μm. The device operation characteristics exhibit a cross-over of the transport regimes, from the ohmic to the space-charge limited current (SCLC) characteristic as a function of the inter-electrode length and the applied bias. The potential landscape imaged using spatially resolved Kelvin-probe measurements indicates the presence of a transport barrier at the metal-MAPbI₃ interface. Additional observation of a finite electric field across the bulk confirms minimal ion-screening effects on the observed transport characteristics. Further, we study the influence of local photo-excitation using near-field scanning photocurrent microscopy. Photocurrent profiles across the device exhibit dominant recombination and charge-separation zones. In the presence of an external bias, the asymmetric photocurrent profile points to the unbalanced nature of carrier transport. These lateral devices exhibit photodetector characteristics with a responsivity of ≈ 54 mA/W in self-powered mode, and ≈ 6.2 A/W at 5 V bias, in short-channel devices (4 μm). Moreover, the low device capacitance enables light-switching transient response of ~12 ns, suitable for high-speed operational applications.