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A new approach to control the n‐doping reaction of organic semiconductors is reported using surface‐functionalized gold nanoparticles (f‐AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n‐type dopant precursor N‐DMBI‐H with several molecular and polymeric semiconductors at different temperatures with/without f‐AuNPs, vis‐à‐vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that while f‐AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~10–140 S cm−1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions and will broaden the use of the corresponding n‐doped films in opto‐electronic devices such as thin‐film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts. [ABSTRACT FROM AUTHOR]

Lead‐free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light‐yellow to black over a temperature range of 10 to 423 K is investigated. First‐principles, density functional theory (DFT)‐based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group‐IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials. [ABSTRACT FROM AUTHOR]

Terahertz (THz) technologies provide opportunities ranging from calibration targets for satellites and telescopes to communication devices and biomedical imaging systems. A main component will be broadband THz absorbers with switchability. However, optically switchable materials in THz are scarce and their modulation is mostly available at narrow bandwidths. Realizing materials with large and broadband modulation in absorption or transmission forms a critical challenge. This study demonstrates that conducting polymer‐cellulose aerogels can provide modulation of broadband THz light with large modulation range from ≈ 13% to 91% absolute transmission, while maintaining specular reflection loss < −30 dB. The exceptional THz modulation is associated with the anomalous optical conductivity peak of conducting polymers, which enhances the absorption in its oxidized state. The study also demonstrates the possibility to reduce the surface hydrophilicity by simple chemical modifications, and shows that broadband absorption of the aerogels at optical frequencies enables de‐frosting by solar‐induced heating. These low‐cost, aqueous solution‐processable, sustainable, and bio‐friendly aerogels may find use in next‐generation intelligent THz devices. [ABSTRACT FROM AUTHOR]

Research on perovskites has grown exponentially in the past decade due to the potential of methyl ammonium lead iodide in photovoltaics. Although these devices have achieved remarkable and competitive power conversion efficiency, concerns have been raised regarding the toxicity of lead and its impact on scaling up the technology. Eliminating lead while conserving the performance of photovoltaic devices is a great challenge. To achieve this goal, the research has been expanded to thousands of compounds with similar or loosely related crystal structures and compositions. Some materials are "re-discovered", and some are yet unexplored, but predictions suggest that their potential applications may go beyond photovoltaics, for example, spintronics, photodetection, photocatalysis, and many other areas. This short review aims to present the classification, some current mapping strategies, and advances of lead-free halide double perovskites, their derivatives, lead-free perovskitoid, and low-dimensional related crystals. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Energy levels and energy level alignment at interfaces play a decisive role in designing efficient and stable organic solar cells (OSCs). In this review two usually used technologies in organic photovoltaic communities for measuring energy levels of organic semiconductors, photoelectron spectroscopy and electrochemical methods, are introduced, and the relationships between the values obtained from the corresponding techniques are compared. The energy level and energy level alignment across the interfaces involved in solution processed organic photovoltaics are described, and the corresponding integer charge transfer model for predicting and explaining energy level alignment is presented. The effects of the interface properties in designing efficient binary and ternary OSCs were discussed. The effects of environmental factors mainly including water vapor, oxygen gas and thermal annealing on energy levels and energy level alignment involved in photoactive layers, and the subsequent effects on the corresponding OSC properties are given. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination at perovskite/charge transport layer heterojunction, seriously limiting their power conversion efficiencies. Herein, solution‐processed chromium multioxide (CrOx) is judiciously selected to construct a MAPbI3/CrOx/Spiro‐OMeTAD hole‐selective heterojunction. It is demonstrated that the inserted CrOx not only effectively reduces defect sites via redox shuttle at perovskite contact, but also decreases valence band maximum (VBM)‐HOMO offset between perovskite and Spiro‐OMeTAD. This will diminish thermionic losses for collecting holes and thus promote charge transport across the heterojunction, suppressing both defect‐assisted recombination and interface carrier recombination. As a result, a remarkable improvement of 21.21% efficiency with excellent device stability is achieved compared to 18.46% of the control device, which is among the highest efficiencies for polycrystalline MAPbI3 based n–i–p planar PSCs reported to date. These findings of this work provide new insights into novel charge‐selective heterojunctions for further enhancing efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) have the potential to revolutionize the field of organic bioelectronics. To date, most of the reported OECTs include p‐type (semi‐)conducting polymers as the channel material, while n‐type OECTs are yet at an early stage of development, with the best performing electron‐transporting materials still suffering from low transconductance, low electron mobility, and slow response time. Here, the high electrical conductivity of multi‐walled carbon nanotubes (MWCNTs) and the large volumetric capacitance of the ladder‐type π‐conjugated redox polymer poly(benzimidazobenzophenanthroline) (BBL) are leveraged to develop n‐type OECTs with record‐high performance. It is demonstrated that the use of MWCNTs enhances the electron mobility by more than one order of magnitude, yielding fast transistor transient response (down to 15 ms) and high μC* (electron mobility × volumetric capacitance) of about 1 F cm−1 V−1 s−1. This enables the development of complementary inverters with a voltage gain of >16 and a large worst‐case noise margin at a supply voltage of <0.6 V, while consuming less than 1 µW of power. [ABSTRACT FROM AUTHOR]

Fluorescent nanohybrids, based on π‐extended hydroxyoxophosphole ligands grafted onto ZnO nanoparticles, are designed and studied. The restriction of the intramolecular motions of the organic fluorophore, through either aggregates' formation in solution or processing into thin films, forms highly emissive materials due to a strong aggregation induced emission effect. Theoretical calculations and XPS analyses were performed to analyze the interactions between the organic and inorganic counterparts. Preliminary results on the use of these nanohybrids as solution‐processed emissive layers in organic light emitting diodes (OLEDs) illustrate their potential for lighting applications. [ABSTRACT FROM AUTHOR]

Persistent photoconductivity (PPC) behavior in organic phototransistors has fascinating potentials in applications of photoelectronic devices. A key issue is how the presence of air affects the PPC behavior. Here, combining with the theoretical and experimental results, the PPC behavior is associated with photogenerated electrons trapped in oxygen atom-induced the reduced Lowest Unoccupied Molecular Orbitals or oxygen molecule-induced new trap state within energy bandgap of organic semiconductor. Inspired by the potential applications arising from the PPC behavior, organic memory phototransistors (OMPTs) are achieved by light programming and electrical erasing. The OMPTs show bistable current states as well as long retention times. Our results suggested that oxygen in air plays a key role in PPC behavior and provides a guidance for controlling the PPC behavior toward integrated multifunctional optoelectronic devices. [Display omitted] • 2DMCs are used as OSCs layer to rule out the influence of grain boundaries on OPTs. • PPC behavior can be obtained when OPTs measured in air compared with OPTs measured under vacuum. • Oxygen-induced trap states play a critical role in PPC behavior. • Memory characteristics arising from PPC behavior are investigated. [ABSTRACT FROM AUTHOR]