A completely amorphous donor polymer PIDT-T8BT recently showed enhanced photovoltaic performance when paired with Y6 using unconventional low donor:acceptor (D:A) ratios, while its analogue PIDT-T12BT achieved high PCEs at conventional 1:1.2 ratios. Two new polymers, PIDT-T6BT and PIDT-T10BT, were synthesized with varying side-chain lengths. All exhibited amorphous phase behavior, with shorter side-chains yielding higher glass transition temperatures. Photovoltaic devices based on PIDT-TxBT (x=6, 8, 10, 12):Y6 were investigated across broad D:A ratios, revealing different optimal ratios for each donor. Thermal stability testing at 85 °C showed low donor content PIDT-T6BT:Y6 (1:10) devices had significantly enhanced stability. Notably, PIDT-T8BT:Y6 (1:10) devices demonstrated superior thermal stability compared to high-performing PM6:Y6 and D18:Y6 systems at both conventional and low D:A ratios. Dynamic mechanical thermal analysis revealed that blends with less polymer retained storage modulus at higher temperatures, indicating enhanced morphological stability, particularly for 1:10 blends. Charge carrier dynamics studies showed that stable 1:10 device performance results from enhanced carrier mobility offsetting decreased carrier lifetime after thermal aging, minimizing charge collection changes. Conversely, PM6:Y6, D18:Y6, and 1:1.2 PIDT-T6BT:Y6 devices exhibited additional performance degradation from poor charge generation due to undesirable phase-separated morphologies.

Conductive soft materials are emerging as critical platforms for interfacing with electrogenic cells, such as neurons and cardiomyocytes. Unlike rigid metal electrodes, these materials offer tuneable conductivity for reliable electrical communication, tissue-like softness for mechanical compliance, and chemical or bioactive functionalities for effective integration with biological systems. However, achieving an optimal balance between the material properties required to control biological functionality, including conductivity, modulus, bending stiffness, charge injection capacity and biocompatibility, remains a significant challenge that is strongly dependent on the fabrication pathway selected. The array of advanced biofabrication methodologies available to researchers continues to expand rapidly, enabling both 'top down' approaches that start with bulk materials and 'bottom up' approaches that enable more precise formation of structures from molecular building blocks. To equip researchers with a practical toolkit for understanding the design trade-offs involved in creating effective bio-interfaces for translation into the clinic in areas such as neuroengineering and cardiac modelling, here we provide a comprehensive review of the interdependencies between material properties, fabrication techniques and functionalisation strategies for these materials, highlighting how they can impact upon the ability to communicate with and control cell behaviour. We first provide an overview of the key interaction mechanisms between electrogenic cells and conductive artificial materials, then introduce some key classes of conductive soft materials, highlighting the impact of their material properties on controlling interactions with electrogenic cells. We then discuss how these material properties are critical for optimising fabrication techniques, with a focus on identifying the strengths and limitations of the array of biofabrciation techniques in the context of specific bioelectronic applications. Subsequently, strategies for tailoring post-fabrication surface chemistry to enhance cell adhesion, growth pathways and prevention of foreign body responses are discussed. Finally, we conclude with a consideration of where these strategies are being employed in both emerging applications (in vitroandin vivo) and clinical translation to create soft conductive bioelectronic devices to address challenges in health and society, highlighting emerging opportunities and potential new directions for the future.

Metal halide perovskites and organic semiconductors have attracted intense interest for ionizing radiation detection due to their advantages of strong attenuation, low leakage currents, synthetic versatility, and simple device manufacturing. These materials present opportunities to develop devices for safer medical imaging and dosimetry, sensing, shielding technologies for space exploration, and improved non‐invasive analysis for security, product inspection, and nuclear safety. However, there is currently a glaring lack of standard approaches for testing and reporting the performance of novel organic semiconductor and perovskite‐based materials and device architectures for radiation detection. This absence of standardization has resulted in a recent exponential increase in publications that lack consistency in both the experimental procedures used for characterization and the interpretation of performance parameters reported. In this Perspective, the major photophysics of organic semiconductors and perovskite materials under high‐energy radiation are summarized, with limitations in evaluating radiation detection performance using metrics designed for highly crystalline inorganic technologies discussed. Finally, key metrics and experimental details that are suggested for reporting in publications to improve reproducibility and enable large data set analysis are identified, noting these procedures are not intended as an exhaustive or definitive list, but rather as a milestone toward enabling improved standardization.

As organic photovoltaics (OPVs) have seen significant advances in performance at both the laboratory and large scale, there is an increased need to develop strategies for improving the overall lifespan under operating conditions. One strategy that has gained significant attraction is the use of solid additives in the active layer to enhance device performance, in addition to photo-/thermal stability of OPV devices. While there are examples of how these additives can influence the physical properties of the bulk-heterojunction (BHJ) morphology, the wide variety of additives used makes it difficult to reach a consensus on their specific functions. Another challenge is that the majority of studies involving solid additives have been conducted on devices fabricated via small-scale spin-coating, with the assumption that these procedures are directly scalable. In this work, the performance of PPDT2FBT:PC61BM devices fabricated via slot-die coating was examined by using four different additives. These included previously reported additives, piperazine (PP), polyacenaphthylene (PAN), and neat C70, as well as one new additive, 4,4'-bipiperidine (BP). The impact of these additives on the thermal stability of the devices was also investigated at two different temperatures, 85 and 120 °C. Devices containing any of the mentioned additives exhibited slightly improved thermal stability at 120 °C, while only the addition of neat C70 improved the device's lifetime at 85 °C. This work demonstrates that, despite solid additives being able to have a positive influence on the thermal stability of OPVs at significantly elevated temperatures, it is essential to investigate thermal stability at temperatures close to the maximum usage temperature.

Development of both organic photovoltaics (OPVs) and organic photocatalysts has focused on utilizing the bulk heterojunction (BHJ). The BHJ promotes charge separation and enhances the carrier lifetime, but may give rise to increased charge traps, hindering performance. Here, high photocatalytic and photovoltaic performance is displayed by electron donor-acceptor (D-A) nanoparticles (NPs) and films, using the nonfullerene acceptor Y6 and polymer donor PIDT-T8BT. In contrast to conventional D-A systems, the charge generation in PIDT-T8BT:Y6 NPs is mainly driven by Y6, allowing a high performance even at a low D:A mass ratio of 1:50. The high performance at the low mass ratio is attributed to the amorphous behavior of PIDT-T8BT. Low ratios are generally thought to yield lower efficiency than the more conventional ≈1:1 ratio. However, the OPVs exhibit peak performance at a D:A ratio of 1:5. Similarly the NPs used for photocatalytic hydrogen evolution show peak performance at the 1:6.7 D:A ratio. Interestingly, for the PIDT-T8BT:Y6 system, as the polymer proportion increases, a reduced photocatalytic and photovoltaic performance is observed. The unconventional D:A ratios provide lower recombination losses and increased charge-carrier lifetime with undisrupted ambipolar charge transport in bulk Y6, enabling better performance than conventional ratios. This work reports novel light-harvesting materials in which performance is reduced due to unfavorable morphology as D:A ratios move toward conventional ratios of 1:1.2-1:1.

Thermal degradation of active layer blend of PPDT2FBT:PCBM deposited via slot-die coating was investigated at 85 °C and 120 °C. The results clearly shows that care must be taken when performing accelerated ageing of OPV materials.

Organic semiconductor-based sensors are a unique class of wearable x-ray detectors, as the response from their carbon-based composition can mimic the response of the human body to radiation. A thin (260 nm) flexible P3HT: o-IDTBR-based organic sensor, deposited onto a conductive Kapton substrate is demonstrated, can provide precise and artifact-free dosimetry under synchrotron x-rays with sensitivities of (1958 +/- 31)pCGy-1cm-2 without bias. The sensor is capable of accurately resolving multiple 50 mu m-wide x-rays with a full-width-half-max of (51.6 +/- 1.9)mu m for a range of energies (47-87.5)keV and dose-rates (0.21-0.45)kGy s-1. Organic sensors fabricated with plastic polyethylene substrates exhibit unreliable x-ray responses and broadening of the full-width-half-max. Simulations reveal that x-ray induced electrostatic charge generated from the polyethylene causes a reverse polarity of the signal. X-ray charge mapping shows the effective area sensitized with the polyethylene device extends twice the length of the pixel area, while sensors with Kapton substrates closely match the expected active area. Radiation tolerance of P3HT:o-IDTBR devices maintain 85.4% of the initial x-ray sensitivity after 10 kGy with similar radiation tolerances to amorphous silicon. This study confirms the unsuitability of polyethylene substrates for flexible radiation detectors, providing the first evidence of the quantitative and spatial resolution limitations created by the generation of radiation-induced charge.

Organic semiconductors have emerged as promising neural interfacing materials due to their innate biocompatibility, soft mechanical properties, and mixed electron/ion conduction. One exciting application is their use as artificial photosensors for retinal prostheses via optically induced neuromodulation. In this study, the optoelectronic and neural interfacing properties of six organic semiconductor polymers and small molecules, split into donor/acceptor pairs that form promising candidates for a trichromatic artificial retina that closely mimics the native response of the human eye are presented. The biocompatibility of these materials using primary human retinal cell cultures by systematic measurement of both cell viability and morphological analysis of retinal ganglion cell neurite elongation over time is investigated. Comparable cell viability between human retinal cell cultures established on all the organic semiconductors and a glass control, which is a standard measurement for biocompatibility in materials science is observed. In contrast, differences in the morphological biocompatibility between the organic semiconductor materials and glass control are detected by analyzing neurite elongation with specific immunomarkers. The difference in the two results has implications for the future assessment of material biocompatibility for bioelectronics, and optimal methodology for assessing morphological biocompatibility in neural interface devices is discussed.

Atomic-scale information about the structural and compositional properties of novel semiconductor nanowires is essential to tailoring their properties for specific applications, but characterization at this length scale remains a challenging task. Here, quasi-1D InAs/InGaAs semiconductor nanowire arrays were grown by selective area epitaxy (SAE) using molecular beam epitaxy (MBE), and their subsequent properties were analyzed by a combination of atom probe tomography (APT) and aberration-corrected transmission electron microscopy (TEM). Results revealed the chemical composition of the outermost thin InAs layer, a fine variation in the indium content at the InAs/InGaAs interface, and lightly incorporated element tracing. The results highlight the importance of correlative microscopy approaches in revealing complex nanoscale structures, with TEM being uniquely suited to interrogating the crystallography of InGaAs NWs, whereas APT is capable of three-dimensional (3D) elemental mapping, revealing the subtle compositional variation near the boundary region. This work demonstrates a detailed pathway for the nanoscale structural assessment of novel one-dimensional (1D) nanomaterials.

This work unravels the intricate relationship between non-fullerene acceptor material surface energy and nanostructure formation in organic nanoparticle colloids.

Abstract:In response to the requirements imposed by the COVID-19 pandemic in 2020, we developed a remote learning undergraduate workshop for 44 students at the University of Newcastle by embedding scanning electron microscope (SEM) images of Maratus (Peacock) spiders into the MyScope Explore environment. The workshop session had two main components: 1) to use the online MyScope Explore tool to virtually image scales with structural color and pigmented color on Maratus spiders; 2) to join a live SEM session via Zoom to image an actual Maratus spider. In previous years, the undergraduate university students attending this annual workshop would enter the Microscopy Facility at the University of Newcastle to image specimens with SEM; however, in 2020 the Microscopy Facility was closed to student visitors, and this virtual activity was developed in order to proceed with the educational event. The program was highly successful and constitutes a platform that can be used in the future by universities for teaching microscopy remotely.

The use of nanostructured materials for targeted and controlled delivery of bioactive molecules is an attractive alternative to conventional drug administration protocols, enabling selective targeting of diseased cells, lower administered dosages, and reduced systemic side effects. Although a variety of nanocarriers have been investigated in recent years, electroactive organic polymer nanoparticles present several exciting advantages. Here we demonstrate that thin films created from nanoparticles synthesized from violanthrone-79, an n-type semiconducting organic material, can incorporate and release dexamethasone in vitro in a highly controlled manner. By systematically altering the nanoparticle formation chemistry, we successfully tailored the size of the nanoparticles between 30 and 145 nm to control the initial amount of drug loaded into the organic particles. The biocompatibility of the different particles was tested using live/dead assays of dorsal root ganglion neurons isolated and cultured from mice, revealing that elevated levels of the sodium dodecyl sulfate surfactant used to create the smaller nanoparticles are cytotoxic; however, cell survival rates in nanoparticles larger than 45 nm exceed 86% and promote neurite growth and elongation. By manipulating the electrical stimulus applied to the electroactive nanoparticle films, we show an accelerated rate of drug release in comparison to passive release in aqueous media. Furthermore, pulsing the electrical stimulus was successfully used to selectively switch the accelerated release rate on and off. By combining the tuning of drug loading (through tailored nanoparticle synthesis) and drug release rate (through electrical stimulus protocols), we demonstrate a highly advanced control of drug delivery dosage in a biocompatible delivery vehicle. This work highlights the significant potential of electroactive organic nanoparticles for implantable devices that can deliver corticosteroids directly to the nervous system for the treatment of inflammation associated with neurological disorders, presenting a translatable pathway toward precision nanomedicine approaches for other drugs and diseases.

A new printable organic semiconducting material combination as a tissue equivalent photodetector for indirect X‐ray detection is demonstrated in this work. The device exhibits a higher optical‐to‐electrical conversion efficiency than any other reported printable organic systems for X‐ray photodetection while also operating efficiently with zero applied bias. Complete X‐ray detectors fabricated by coupling the photodiode with a plastic scintillator are among the first flexible and fully tissue equivalent X‐ray detectors capable of operating without external bias. The response to X‐rays is energy independent between 50 keV and 1.2 MeV, with a detection sensitivity equivalent to inorganic direct X‐ray detectors and one of the fastest temporal responses ever reported for organic X‐ray detectors. The materials can be printed into arrays with a pixel pitch of 120 μm, providing 2D spatial detection. The devices are found to be highly stable with respect to time, mechanical flexing, and large (5 kGy) radiation doses. The new materials and fully tissue equivalent X‐ray detectors reported here provide stable, printable, flexible, and tissue equivalent detectors with a high radiolucency that are ideally suited for wearable applications, where simultaneous monitoring and high transmission of the X‐ray absorbed dose into the human body is required.

Advances in flexible and printable electronics have paved the way for large-area, and low-cost wearable electronics that will revolutionize the way we detect and monitor ionizing radiation. The improvements to early detection and widespread use of treatment procedures of tumors and other illnesses using ionizing radiation have led to the rapid increase in the yearly dose exposure to the public. Therefore, safety organizations must introduce stricter quality assurance measures to ensure the safe delivery of the total dose to the patient—only achievable using live monitoring systems, named in-vivo dosimetry. Such systems would also benefit the safety of professional personnel employed in areas that encounter higher exposures of ionizing radiation including nuclear plants, space exploration, flight staff, and research beamline facilities. However, the current real-time detectors employ expensive and rigid high-Z materials including silicon, germanium, and cadmium telluride, that suffer substantial limitations in monitoring the dose deposited in biological tissue and conforming to the complex contours of the human body over large areas. We provide insights into the innovative materials capable of solution-based device fabrication onto flexible substrates with foreseeable avenues towards low-cost large-area printing techniques. This discussion will also review and identify the advantages and existing capabilities of tissue-equivalent materials in the detection of ionizing radiation as the ideal materials for in-vivo dosimetry. Finally, the radiation tolerance of organic materials is outlined to demonstrate that extensive investigations are still required before their utilization as radiation detectors.

The use of organic semiconductor devices as photocapacitors is an innovation with promising applications in neural interface technologies, particularly for retinal prosthetics. Here we report the characterization of four distinct photocapacitor device architectures that were fabricated by depositing ultra-thin layers of poly-3-hexylthiophene and C60 fullerene in various combinations on tin-doped indium oxide (ITO) electrodes. We used electrophysiological recordings to measure the intrinsic photoresponse at 470 nm, and also to determine light-induced voltage perturbations in electrolyte solutions interfaced with these semiconductors. We also determined the light-induced intracellular voltage changes in co-cultured sensory neurons. Electrochemical impedance spectroscopy was used to establish the photocapacitive response mechanism of the intracellular changes upon illumination. The largest amplitude photocapacitive response was elicited from a neuron/acceptor-donor bilayer/ITO device architecture, whilst reversing the donor and acceptor layer order enabled a neuron response of the opposite polarity. The photoresponse in the neuron/acceptor/donor/ITO bilayer device configuration was significantly enhanced in both amplitude and time duration by electrical grounding of the indium tin oxide layer. We describe the advantages and limitations of each configuration of these device and discuss pathways towards the creation of optically triggered neural interfaces that do not require an external electrical power supply.

This work reports the development of a highly sensitive pressure detector prepared by inkjet printing of electroactive organic semiconducting materials. The pressure sensing is achieved by incorporating a quantum tunnelling composite material composed of graphite nanoparticles in a rubber matrix into the multilayer nanostructure of a printed organic thin film transistor. This printed device was able to convert shock wave inputs rapidly and reproducibly into an inherently amplified electronic output signal. Variation of the organic ink material, solvents, and printing speeds were shown to modulate the multilayer nanostructure of the organic semiconducting and dielectric layers, enabling tuneable optimisation of the transistor response. The optimised printed device exhibits rapid switching from a non-conductive to a conductive state upon application of low pressures whilst operating at very low source-drain voltages (0–5 V), a feature that is often required in applications sensitive to stray electromagnetic signals but is not provided by conventional inorganic transistors and switches. The printed sensor also operates without the need for any gate voltage bias, further reducing the electronics required for operation. The printable low-voltage sensing and signalling system offers a route to simple low-cost assemblies for secure detection of stimuli in highly energetic systems including combustible or chemically sensitive materials.

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