Solvent-dripping modulated 3D/2D heterostructures for high-performance perovskite solar cells.

The controlled growth of two-dimensional (2D) perovskite atop three-dimensional (3D) perovskite films reduces interfacial recombination and impedes ion migration, thus improving the performance and stability of perovskite solar cells (PSCs). Unfortunately, the random orientation of the spontaneously formed 2D phase atop the pre-deposited 3D perovskite film can deteriorate charge extraction owing to energetic disorder, limiting the maximum attainable efficiency and long-term stability of the PSCs. Here, we introduce a meta-amidinopyridine ligand and the solvent post-dripping step to generate a highly ordered 2D perovskite phase on the surface of a 3D perovskite film.

Significant Efficiency Enhancements in Non-Y Series Acceptors by the Addition of Outer Side Chains.

Most current highly efficient organic solar cells utilize small molecules like Y6 and its derivatives as electron acceptors in the photoactive layer. In this work, a small molecule acceptor, SC8-IT4F, is developed through outer side chain engineering on the terminal thiophene of a conjugated 6,12-dihydro-dithienoindeno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IDTT) central core. Compared to the reference molecule C8-IT4F, which lacks outer side chains, SC8-IT4F displays notable differences in molecule geometry (as shown by simulations), thermal behavior, single-crystal packing, and film morphology.

Ultra-Fast Moisture Sensor for Respiratory Cycle Monitoring and Non-Contact Sensing Applications.

As human-machine interface hardware advances, better sensors are required to detect signals from different stimuli. Among numerous technologies, humidity sensors are critical for applications across different sectors, including environmental monitoring, food production, agriculture, and healthcare. Current humidity sensors rely on materials that absorb moisture, which can take some time to equilibrate with the surrounding environment, thus slowing their temporal response and limiting their applications.

Conjugation Length Dependence of Intramolecular Singlet Fission in a Series of Regioregular Oligo 3-Alkyl(thienylene-vinylene)s.

Activated intramolecular singlet fission is known to occur in the conjugated polymer polythienylene-vinylene (P3TV). Instead, efficient intersystem crossing has been observed in a short 3-alkyl(thienylene-vinylene) dimer. Here, we investigate a series of oligomers covering the conjugation length gap between the dimer and polymer.

Thiol Carbazole Self-Assembled Monolayers as Tunable Carrier Injecting Interlayers for Organic Transistors and Complementary Circuits.

The significant contact resistance at the metal-semiconductor interface is a well-documented issue for organic thin-film transistors (OTFTs) that hinders device and circuit performance. Here, this issue is tackled by developing three new thiol carbazole-based self-assembled monolayer (SAM) molecules, namely tBu-2SCz, 2SCz, and Br-2SCz, and utilizing them as carrier-selective injection interlayers. The SAMs alter the work function of gold electrodes by more than 1 eV, making them suitable for use in hole and electron-transporting OTFTs.

Energy Level Tuning in Conjugated Donor Polymers by Chalcogen Exchange for Low Dark Current Organic Photodetectors.

The performance of organic photodetectors (OPDs) using conjugated polymer donors and molecular acceptors has improved rapidly, but many polymers are difficult to upscale due to their complex structures. This study examines two low-complexity thiophene copolymers with substituted benzooxadiazole () or benzothiadiazole (). Substituting sulfur with oxygen in increased its ionization energy without affecting the optical gap.

High Performance Organic Mixed Ionic-Electronic Polymeric Conductor with Stability to Autoclave Sterilization.

We present a series of newly developed donor-acceptor (D-A) polymers designed specifically for organic electrochemical transistors (OECTs) synthesized by a straightforward route. All polymers exhibited accumulation mode behavior in OECT devices, and tuning of the donor comonomer resulted in a three-order-of-magnitude increase in transconductance. The best polymer gFBT-g2T, exhibited normalized peak transconductance (g) of 298±10.

Downscaling of Organic Field-Effect Transistors based on High-Mobility Semiconducting Blends for High-Frequency Operation.

Small molecule/polymer semiconductor blends are promising solutions for the development of high-performing organic electronics. They are able to combine ease in solution processability, thanks to the tunable rheological properties of polymeric inks, with outstanding charge transport properties thanks to high crystalline phases of small molecules. However, because of charge injection issues, so far such good performances are only demonstrated in ad-hoc device architectures, not suited for high-frequency applications, where transistor dimensions require downscaling.

Non-equilibrium transport in polymer mixed ionic-electronic conductors at ultrahigh charge densities.

Conducting polymers are mixed ionic-electronic conductors that are emerging candidates for neuromorphic computing, bioelectronics and thermoelectrics. However, fundamental aspects of their many-body correlated electron-ion transport physics remain poorly understood. Here we show that in p-type organic electrochemical transistors it is possible to remove all of the electrons from the valence band and even access deeper bands without degradation.

Over 19% Efficient Inverted Organic Photovoltaics Featuring a Molecularly Doped Metal Oxide Electron-Transporting Layer.

Molecular doping is commonly utilized to tune the charge transport properties of organic semiconductors. However, applying this technique to electrically dope inorganic materials like metal oxide semiconductors is challenging due to the limited availability of molecules with suitable energy levels and processing characteristics. Herein, n-type doping of zinc oxide (ZnO) films is demonstrated using 1,3-dimethylimidazolium-2-carboxylate (CO-DMI), a thermally activated organic n-type dopant.

Hierarchical Solid-Additive Strategy for Achieving Layer-by-Layer Organic Solar Cells with Over 19 % Efficiency.

Layer-by-layer (LbL) deposition of active layers in organic solar cells (OSCs) offers immense potential for optimizing performance through precise tailoring of each layer. However, achieving high-performance LbL OSCs with distinct solid additives in each layer remains challenging. In this study, we explore a novel approach that strategically incorporates different solid additives into specific layers of LbL devices.

Photocatalytic doping of organic semiconductors.

Chemical doping is an important approach to manipulating charge-carrier concentration and transport in organic semiconductors (OSCs) and ultimately enhances device performance. However, conventional doping strategies often rely on the use of highly reactive (strong) dopants, which are consumed during the doping process. Achieving efficient doping with weak and/or widely accessible dopants under mild conditions remains a considerable challenge.

A Conjugated Carboranyl Main Chain Polymer with Aggregation-Induced Emission in the Near-Infrared.

Materials exhibiting aggregation-induced emission (AIE) are both highly emissive in the solid state and prompt a strongly red-shifted emission and should therefore pose as good candidates toward emerging near-infrared (NIR) applications of organic semiconductors (OSCs). Despite this, very few AIE materials have been reported with significant emissivity past 700 nm. In this work, we elucidate the potential of -carborane as an AIE-active component in the design of NIR-emitting OSCs.

Label-Free Metal-Oxide Transistor Biosensors for Metabolite Detection in Human Saliva.

Metabolites are essential molecules involved in various metabolic processes, and their deficiencies and excessive concentrations can trigger significant physiological consequences. The detection of multiple metabolites within a non-invasively collected biofluid could facilitate early prognosis and diagnosis of severe diseases. Here, a metal oxide heterojunction transistor (HJ-TFT) sensor is developed for the label-free, rapid detection of uric acid (UA) and 25(OH)Vitamin-D3 (Vit-D3) in human saliva.

Fast Near-Infrared Photodetectors Based on Nontoxic and Solution-Processable AgBiS.

Solution-processable near-infrared (NIR) photodetectors are urgently needed for a wide range of next-generation electronics, including sensors, optical communications and bioimaging. However, it is rare to find photodetectors with >300 kHz cut-off frequencies, especially in the NIR region, and many of the emerging inorganic materials explored are comprised of toxic elements, such as lead. Herein, solution-processed AgBiS photodetectors with high cut-off frequencies under both white light (>1 MHz) and NIR (approaching 500 kHz) illumination are developed.

Reducing undesired solubility of squarephaneic tetraimide for use as an organic battery electrode material.

Locally aromatic alkyl--substituted squarephaneic tetraimide (SqTI) conjugated macrocycles are four-electron reducible, owing to global aromaticity and presumed global Baird aromaticity of the dianion and tetraanion states, respectively. However, their good solubility inhibits their application as a battery electrode material. By applying sidechain removal as a strategy to reduce SqTI solubility, we report the development of its unsubstituted derivative SqTI-H, which was obtained directly from squarephaneic tetraanhydride by facile treatment with hexamethyldisilazane and MeOH.

Tissue Equivalent Curved Organic X-ray Detectors Utilizing High Atomic Number Polythiophene Analogues.

Organic semiconductors are a promising material candidate for X-ray detection. However, the low atomic number (Z) of organic semiconductors leads to poor X-ray absorption thus restricting their performance. Herein, the authors propose a new strategy for achieving high-sensitivity performance for X-ray detectors based on organic semiconductors modified with high -Z heteroatoms.

A polymer library enables the rapid identification of a highly scalable and efficient donor material for organic solar cells.

The dramatic improvement of the PCE (power conversion efficiency) of organic photovoltaic devices in the past few years has been driven by the development of new polymer donor materials and non-fullerene acceptors (NFAs). In the design of such materials synthetic scalability is often not considered, and hence complicated synthetic protocols are typical for high-performing materials. Here we report an approach to readily introduce a variety of solubilizing groups into a benzo[][1,2,5]thiadiazole acceptor comonomer.

p-Type Conjugated Polymers Containing Electron-Deficient Pentacyclic Azepinedione.

Bisthienoazepinedione (BTA) has been reported for constructing high-performing p-type conjugated polymers in organic electronics, but the ring extended version of BTA is not well explored. In this work, we report a new synthesis of a key building block to the ring expanded electron-deficient pentacyclic azepinedione (BTTA). Three copolymers of BTAA with benzodithiophene substituted by different side chains are prepared.

Biorenewable Solvents for High-Performance Organic Solar Cells.

With the advent of nonfullerene acceptors (NFAs), organic photovoltaic (OPV) devices are now achieving high enough power conversion efficiencies (PCEs) for commercialization. However, these high performances rely on active layers processed from petroleum-based and toxic solvents, which are undesirable for mass manufacturing. Here, we demonstrate the use of biorenewable 2-methyltetrahydrofuran (2MeTHF) and cyclopentyl methyl ether (CPME) solvents to process donor: NFA-based OPVs with no additional additives in the active layer.