The phenomenon of charge carrier traps in organic semiconductors and their impact on electronic devices are reviewed.

Indeno[1,2-b]fluorenes (IFs), while containing 4n π-electrons, are best described as two aromatic benzene rings fused to a weakly paratropic s-indacene core. In this study, we find that replacement of the outer benzene rings of an IF with benzothiophenes allows the antiaromaticity of the central s-indacene to strongly reassert itself. Herein we report a combined synthetic, computational, structural, and materials study of anti- and syn-indacenodibenzothiophenes (IDBTs). We have developed an efficient and scalable synthesis for preparation of a series of aryl- and ethynyl-substituted IDBTs. NICS-XY scans and ACID calculations reveal an increasingly antiaromatic core from [1,2-b]IF to anti-IDBT, with syn-IDBT being nearly as antiaromatic as the parent s-indacene. As an initial evaluation, the intermolecular electronic couplings and electronic band structure of a diethynyl anti-IDBT derivative reveal the potential for hole and / or electron transport. OFETs constructed using this molecule show the highest hole mobilities yet achieved for a fully conjugated IF derivative.

cells based on HOIPs have witnessed an unprecedented growth in efficiency in only a few years, faster than any PV technology to date, with power conversion efficiencies greater than 20%. [8] In addition, HOIPs have been incorporated in photodetectors, [9] optically pumped lasers with tunable wavelength, [10] and highefficiency light-emitting diodes. [3] Remarkably, all these devices were manufactured at temperatures below or around 100 °C.The small electron effective mass calculated for HOIPs suggests that the charge carrier mobilities, µ, may be very high in absence of defects and other scattering sites. [11,12] Indeed, mobilities exceeding 100 cm 2 V −1 s −1 were determined in single crystals from space charge limited current (SCLC) and terahertz (THz) spectroscopy measurements. [6,7] The mobilities obtained from field-effect transistors (FETs), however, have been much lower; a maximum value of around 1 cm 2 V −1 s −1 was reported in MAPbX 3 perovskite FETs, [13][14][15] and a maximum of around 2 cm 2 V −1 s −1 in Cs x (M A 0.17 FA 0.83 ) 1−x Pb(Br 0.17 I 0.83 ) 3 triple cation perovskites, [16] despite significant effort dedicated to this topic. [17][18][19][20][21][22] The discrepancy between the measured mobilities with various techniques may arise from the fact that in FETs the interface properties are evaluated, which are prone to defects, whereas the other methods access the bulk properties. On the other hand, recent work suggests that the high mobility values in hybrid perovskites may be an overestimation since the charge transport in these compounds is inhibited due to the existence of a plethora of processes such as polaron formation, [23] scattering from acoustic and optical phonons, [5,11,24] ionic motion, polarization disorder of the organic cations, and dynamic disorder. [14,18,25] A roomtemperature mobility of ≈200 cm 2 V −1 s −1 was predicted in MAPbI 3 in the presence of phonon scattering alone, with no other factors that limit charge carrier transport. [11] It is critical to assess the true intrinsic electrical properties of hybrid perovskites to advance their use in commercial optoelectronic applications. FETs are excellent experimental platforms to access such information with minimal or no approximations necessary. In addition to being the fundamental unit in a wide range of electronic applications, FET devices allow for a basic study of the factors limiting charge transport in perovskites, with a great control over the charge density in the semiconductor layer. Unfortunately, because of the challenges associated with Hybrid organic-inorganic perovskites have recently gained immense attention due to their unique optical and electronic properties and low production cost, which make them promising candidates for a wide range of optoelectronic devices. But unlike most other technologies, the breakthroughs witnessed in hybrid perovskite optoelectronics have outgrown the basic understanding of the fundamental material properties. For example, the effectiveness of charge transport in relation to f...

Charge-carrier transport in thin-film organic semiconductors is strongly related to the molecular structure and the solid-state packing, which in turn are dependent on materials processing and device configurations. We report on the synthesis and characterization of a series of  (trialkylsilyl)­ethynyl-substituted dinaphtho-fused s-indacenes that include three regioisomers: the linear, syn, and anti isomers. Structure–property relationships are established for these antiaromatic compounds by combining X-ray diffraction with field-effect transistor measurements and density functional theory (DFT) evaluations of the electronic band structures and intermolecular electronic couplings. High-performance, solution-processed organic thin-film transistors with charge-carrier mobilities over 7 cm2/(V s) are demonstrated upon optimization of the thin-film morphology. The DFT-derived crystal band structures provide insight into the varied performance metrics observed across the materials, though the fundamental limits of performance are not reached when the film quality is poor. The totality of the results presents the antiaromatic dinaphtho-fused s-indacenes as intriguing building blocks for molecular materials for semiconducting applications.

Layered lead halide perovskites have recently been heavily investigated due to their versatile structures, tunable electronic properties, and better stability compared with 3D perovskites and have also been effectively incorporated into photovoltaic and light-emitting devices. They are often prepared into thin film form by solution methods and typically contain a mixture of phases with different inorganic layer thicknesses (denoted by "n"). In addition, melt-processing has recently been introduced as an option for film deposition of n = 1 lead iodide-based perovskites. Here, we study the thermal properties of higher n (n > 1) layered perovskites in the family (β-Me-PEA) 2 MA n−1 Pb n I 3n+1 , with n = 1, 2, and 3 and where β-Me-PEA = β-methylphenethylammonium and MA = methylammonium, and reveal that they do not melt congruently. However, they can still be melt-processed in air by using a two-step process that includes a lower temperature postannealing step after the initial brief melting step. While typically higher n films contain a mixture of the different n phases, the resulting two-step melt-processed films are highly crystalline and phase pure. Optical and electrical properties of these films were further characterized by time-resolved photoluminescence and dark/illuminated transport measurements, showing the same order of magnitude single-exciton recombination rates compared to previous single crystal results and >2 orders of magnitude higher conductivity compared to conventional spin-coated films. These results offer new pathways to study the layered perovskites and to integrate them into electronic and optoelectronic devices.

Solution-processable electronic devices are highly desirable due to their low cost and compatibility with flexible substrates. However, they are often challenging to fabricate due to the hydrophobic nature of the surfaces of the constituent layers. Here, we use a protein solution to modify the surface properties and to improve the wettability of the fluoropolymer dielectric Cytop. The engineered hydrophilic surface is successfully incorporated in bottom-gate solution-deposited organic field-effect transistors (OFETs) and hybrid organic-inorganic trihalide perovskite field-effect transistors (HTP-FETs) fabricated on flexible substrates. Our analysis of the density of trapping states at the semiconductor-dielectric interface suggests that the increase in the trap density as a result of the chemical treatment is minimal. As a result, the devices exhibit good charge carrier mobilities, near-zero threshold voltages, and low electrical hysteresis.

Crystallization from solutions containing 2,2′-[naphthalene-1,8:4,5bis(dicarboximide)-N,N′-diyl]-bis(ethylammonium) diiodide ((NDIC2)I 2 ) and PbI 2 has been investigated. Eight different materials are obtained, either by variation of crystallization conditions or by subsequent thermal or solvent-induced transformations. Crystal structures have been determined for five materials. 5) form 1-dimensional (1D) chains consisting of PbI 6 (and, in the case of 1, PbI 5 (DMF)) octahedra, either solely facesharing or a mixture of face-sharing and vertex-sharing. The structure of [(NDIC 2 ) 3 Pb 5 I 16 ]•6NMP (2) contains 0D clusters; these consist of three PbI 6 octahedra and two unusually coordinated lead centers that exhibit three relatively short Pb−I bonds, two very long Pb−I contacts, and η 2 -coordination of an aromatic ring of NDIC2 to the lead. Close contacts between iodide ions and the imide rings of NDIC2 in four of the structures suggest that an iodide-to-NDIC2 charge-transfer interaction may be responsible for the observed red coloration of the materials. The optical and electrical properties of 1 have been studied; its onset of absorption is at 2.0 eV, and its conductivity was measured as 5.4 × 10 −5 ± 1.1 × 10 −5 S m −1 .

Solution‐processable organic semiconductors can serve as the basis for new products including rollable displays, tattoo‐like smart bandages for real‐time health monitoring, and conformable electronics integrated into clothing or even implanted in the human body. For such exciting commercial applications to become a reality, good device performance and uniformity over large areas are necessary. The design of new materials has progressed at an astonishing pace, but accessing their intrinsic, efficient electrical properties in large‐area flexible device arrays is difficult. The development of protocols that allow integration with industrial‐scale processing for high‐throughput manufacturing, without the need to compromise on performance, is the key for transitioning these materials to real‐life applications. In this work, large‐area arrays of organic thin‐film transistors obtained by spray‐coating the high‐mobility polymer indacenodithiophene‐co‐benzothiadiazole (IDTBT) are demonstrated. A maximum charge carrier mobility of 2.3 cm2 V−1 s−1, with a very narrow performance distribution, is obtained over surface areas of 10 cm × 10 cm. The devices retain their electrical properties when bent multiple times and at different curvatures. In addition, large arrays of highly sensitive (0.25% change in mobility for 1% humidity variation), reusable, near‐identical humidity sensors are produced in a one‐step fabrication and calibrated from 0% to 94% relative humidity.