Singlet fission and triplet-triplet annihilation represent two highly promising ways of increasing the efficiency of photovoltaic devices. Both processes are believed to be mediated by a biexcitonic triplet-pair state, 1 (TT). Recently however, controversy has arisen over the role of 1 (TT) in triplet-triplet annihilation.Here we use intensity-dependent, low-temperature photoluminescence measurements, combined with kinetic modelling, to show that distinct 1 (TT) emission arises directly from triplet-triplet annihilation in high-quality pentacene single crystals and anthradithiophene (diF-TES-ADT) thin films. This work demonstrates that a real, emissive triplet-pair state acts as an intermediate in both singlet fission and triplet-triplet annihilation and that this is true for both endo-and exo-thermic singlet fission materials.

Dense layers of semiconducting single-walled carbon nanotubes (SWNTs) serve as electrochromic (EC) materials in the near-infrared with high optical density and high conductivity. EC cells with tunable notch filter properties instead of broadband absorption are created via highly selective dispersion of specific semiconducting SWNTs through polymer-wrapping followed by deposition of thick films by aerosol-jet printing. A simple planar geometry with spray-coated mixed SWNTs as the counter electrode renders transparent metal oxides redundant and facilitates complete bleaching within a few seconds through iongel electrolytes with high ionic conductivities. Monochiral (6,5) SWNT films as working electrodes exhibit a narrow absorption band at 997 nm (full width at half-maximum of 55–73 nm) with voltage-dependent optical densities between 0.2 and 4.5 and a modulation depth of up to 43 dB. These (6,5) SWNT notch filters can retain more than 95% of maximum bleaching for several hours under open-circuit conditions. In addition, different levels of transmission can be set by applying constant low voltage (1.5 V) pulses with modulated width or by a given number of fixed short pulses.

The ability to prepare uniform and dense networks of purely semiconducting single-walled carbon nanotubes (SWNTs) has enabled the design of various (opto-)electronic devices, especially field-effect transistors (FETs) with high carrier mobilities. Further optimization of these SWNT networks is desired to surpass established solution-processable semiconductors. The average diameter and diameter distribution of nanotubes in a dense network were found to influence the overall charge carrier mobility; e.g., networks with a broad range of SWNT diameters show inferior transport properties. Here, we investigate charge transport in FETs with nanotube networks comprising polymer-sorted small diameter (6,5) SWNTs (0.76 nm) and large diameter plasma torch SWNTs (1.17−1.55 nm) in defined mixing ratios. All transistors show balanced ambipolar transport with high on/off current ratios and negligible hysteresis. While the range of bandgaps in these networks creates a highly uneven energy landscape for charge carrier hopping, the extracted hole and electron mobilities vary nonlinearly with the network composition from the lowest mobility (15 cm 2 V −1 s −1 ) for only (6,5) SWNT to the highest mobility (30 cm 2 V −1 s −1 ) for only plasma torch SWNTs. A comparison to numerically simulated network mobilities shows that a superposition of thermally activated hopping across SWNT−SWNT junctions and diameter-dependent intratube transport is required to reproduce the experimental data. These results also emphasize the need for monochiral large diameter nanotubes for maximum carrier mobilities in random networks.

Solution‐processed, low cost thin films of layered semiconductors such as transition metal dichalcogenides (TMDs) are potential candidates for future printed electronics. Here, n‐type electrolyte‐gated transistors (EGTs) based on porous WS2 nanosheet networks as the semiconductor are demonstrated. The WS2 nanosheets are liquid phase exfoliated to form aqueous/surfactant stabilized inks, and deposited at low temperatures (T < 120 °C) in ambient atmosphere by airbrushing. No solvent exchange, further additives, or complicated processing steps are required. While the EGTs are primarily n‐type (electron accumulation), some hole transport is also observable. The EGTs show current modulations > 104 with low hysteresis, channel width‐normalized on‐conductances of up to 0.27 µS µm−1 and estimated electron mobilities around 0.01 cm2 V−1 s−1. In addition, the WS2 nanosheet networks exhibit relatively high volumetric capacitance values of 30 F cm−3. Charge transport within the network depends significantly on the applied lateral electric field and is thermally activated, which supports the notion that hopping between nanosheets is a major limiting factor for these networks and their future application.

Vibrational spectroscopies, such as Raman and Fouriertransform infrared spectroscopy (FT-IR), are powerful tools for the characterization of organic semiconductor thin films and crystals in addition to X-ray diffraction and scanning atomic force microscopy. They enable the investigation of molecular orientation, polymorphism, doping levels, and intra-as well as intermolecular vibrational modes albeit without much spatial resolution. Two fundamentally different scanning probe techniques offer two-dimensional mapping of infraredactive modes with a spatial resolution below 100 nm: scattering-type scanning near-field optical microscopy (IR s-SNOM) and atomic force microscopy-infrared spectroscopy (AFM-IR). Here, we compare these two techniques with each other and to conventional FT-IR spectroscopy measurements with regard to their applicability to highly ordered molecular semiconductors. For this purpose, we use organic single crystals of rubrene, perfluorobutyldicyanoperylene carboxydiimide (PDIF-CN 2 ), TIPS-pentacene, and TIPStetraazapentacene as model systems. We find significant spectral differences depending on the technique and polarization that are related to the anisotropy of the crystals and the fundamentally different working principles of the applied methods. The spatial and spectral resolution of IR s-SNOM and AFM-IR are further tested and compared for a polycrystalline thin film of PDIF-CN 2 .