Trap states generated at grain boundaries often dominate the charge transport behavior of polycrystalline organic field effect transistors (OFETs). While these grain boundaries can be reduced through careful processing, unfortunately they cannot be completely suppressed. In this work, we introduce an approach that renders the grain boundaries inactive. Diels-Alder chemistry, which selectively reacts at the grain boundaries within organic semiconductor thin films, is utilized to attach a dipole-containing molecule in a localized manner. This induced dipole alters the surface potential, shifting the mean energy within the grain boundary and resulting in significantly enhanced device performance. Conductance increases exceed two orders of magnitude with the increase proportional to the amount of grain boundary reacted. In OFETs, this generated a doubling in charge carrier mobility and a reduction in the threshold voltage. The ability to tune the performance and uniformity of fabricated films, regardless of their initial grain size or conductance, represents a significant advance in post-fabrication optimization.

Organic dosimeters offer unique advantages over traditional technologies, and they can be used to expand the capabilities of current radiation detection systems. In-depth knowledge of the mechanisms underlying the interaction between radiation and organic materials is essential for their widespread adoption. Here, we identified and quantitatively characterized the electronic traps generated during the operation of radiation dosimeters based on organic field-effect transistors. Spectral analysis of the trap density of states, along with optical and structural studies, revealed the origin of trap states as local structural disorder within the crystalline films. Our results provide new insights into the radiation-induced defects in organic dosimeters, and pave the way for the development of more efficient and reliable radiation detection devices.

Development of organic field-effect transistors (OFETs) that simultaneously exhibit high-performance and high-stability is critical for complementary integrated circuits and other applications based on organic semiconductors. While progress has been made in enhancing p-channel devices, engineering competitive n-type organic transistors remains a formidable obstacle. Herein, we demonstrate the achievement of high-mobility n-type OFETs with unprecedented operational stability through innovative device and material engineering. Thin film transistors fabricated on donor-acceptor polymers based on indacenodithiazole (IDTz) and diketopyrrolopyrrole (DPP) units exhibit electron mobilities up to 1.3 cm2 V-1 s-1, along with a negligible change in mobility, and threshold voltage shift as low as 0.5 V under continuous bias stress of 60 V for both the gate-source and drain-source voltages persisting for more than 1000 min. These remarkable properties position our OFETs as formidable counterparts to p-type transistors, addressing a longstanding challenge in the field. High-mobility n-type organic transistors that maintain performance for over 1000 minutes under bias stress pave the way for complementary organic circuits, overcoming a key obstacle in the field.

Perovskite optoelectronics are regarded as a disruptive technology, but their susceptibility to environmental degradation and reliance on toxic solvents in traditional processing methods pose significant challenges to their practical implementation. Herein, methylammonium lead iodide (MAPbI(3)) perovskite films processed via a solvent-free laser printing technique, that exhibit exceptional stability, are reported. These films withstand extreme conditions, including high doses of X-ray radiation exceeding 200 Gy, blue laser illumination, 90% relative humidity, and thermal stress up to 80 degrees C for over 300 min in air. We demonstrate that laser-printed films maintain their structural integrity and optoelectronic properties even after prolonged exposure to these stressors, significantly surpassing the stability of conventionally processed films. The enhanced stability is attributed to the unique film formation mechanism and resulting defect-tolerant microstructure. These results underscore the potential of laser printing as a scalable, safe, and sustainable manufacturing route for producing stable perovskite-based devices with potential applications in diverse fields, ranging from renewable energy to large-area electronics and space exploration.

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g. via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g. printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world.

Organic semiconductors enable low-cost solution processing of optoelectronic devices on flexible substrates. Their use in contemporary applications, however, is sparse due to persistent challenges in achieving the requisite performance levels in a reliable and reproducible manner. A critical bottleneck is the inefficiency associated with charge injection. Here, large-scale simulations are employed to identify operational windows where key device parameters that are difficult to control experimentally, such as the contact resistance, become less consequential to overall device functionality. This design methodology overcomes injection barrier limitations in organic field-effect transistors (OFETs), leading to high charge carrier mobility and significantly expanding the range of suitable electrode materials. Leveraging this new understanding, all-organic, solution-deposited OFETs are successfully fabricated on flexible substrates. These devices incorporate printed contacts and showcase mobilities exceeding 5 cm2 Vs-1. These results provide a route for accessing the fundamental limits of material properties even in the absence of ideal contacts - a critical step in establishing reliable structure/property relationships and optimal material design paradigms. While reducing the injection barrier and contact resistance remains critical for achieving high OFET performance, this work demonstrates a path toward consistently achieving high charge carrier mobility through device geometry design, ultimately reducing processing complexity and cost.

In addition to optimizing the charge carrier mobility (μ) in organic semiconductor devices, it is critical to improve operational stability. We investigated organic field-effect transistors (OFETs) made from several conjugated polymers based on indacenodithiazole (IDTz). Surface treatment of the electrode enabled us to tune the transport from p-type to n-type, while thermal annealing improved μ to 1.35 cm2/Vs. We bias-stressed the OFETs for about 24h hours at constant DC conditions (VGS= VDS= 60V) and found that in the most optimized devices only minor changes in the properties occur, i.e. 3% decrease in mobility and threshold voltage shift of maximum 2V.

2-Dimensional brickwork packing is desirable for high mobility organic semiconductors. We synthesised acene derivatives that adopt this packing without using heavier group 14 elements to investigate substituent effects on bulk transport properties.

Acenes have been utilised as organic semiconductors for the last few decades. Attaching ethynyl groups to their core increases stability and solubility, allowing solution processing of these materials into opto-electronic devices. Side chain engineering can control the solid-state packing and affect charge transport in OFET devices. We report on the use of carbon side chains in place of the ubiquitous alkylsilyl groups, where subtle changes dramatically affect the crystal packing and therefore the applicability of these materials for use in organic electronics. Changes in sidechain can also affect the molecular properties and in particular the photostability of these materials.