In this work, we examine the effect of microstructure on ion-migrationinduced photoluminescence (PL) quenching in methylammonium lead iodide perovskite films. Thin films were fabricated by two methods: spin-coating, which results in randomly oriented perovskite grains, and zone-casting, which results in aligned grains. As an external bias is applied to these films, migration of ions causes a quenching of the PL signal in the vicinity of the anode. The evolution of this PLquenched zone is less uniform in the spin-coated devices than in the zone-cast ones, suggesting that the relative orientation of the crystal grains plays a significant role in the migration of ions within polycrystalline perovskite. We simulate this effect via a simple Ising model of ionic motion across grains in the perovskite thin film. The results of this simulation align closely with the observed experimental results, further solidifying the correlation between crystal grain orientation and the rate of ionic transport.

Solution-processed networks of semiconducting, single-walled carbon nanotubes (SWCNTs) have attracted considerable attention as materials for next-generation electronic devices and circuits. However, the impact of the SWCNT network composition on charge transport on a microscopic level remains an open and complex question. Here, we use charge-modulated absorption and photoluminescence spectroscopy to probe exclusively the mobile charge carriers in monochiral (6,5) and mixed SWCNT network field-effect transistors. Ground state bleaching and charge-induced trion absorption features, as well as exciton quenching are observed depending on applied voltage and modulation frequency. Through correlation of the modulated mobile carrier density and the optical response of the nanotubes, we find that charge transport in mixed SWCNT networks depends strongly on the diameter and thus bandgap of the individual species. Mobile charges are preferentially transported by small bandgap SWCNTs especially at low gate voltages, whereas large bandgap species only start to participate at higher carrier concentrations. Our results demonstrate the excellent suitability of modulation spectroscopy to investigate charge transport in nanotube network transistors and highlight the importance of SWCNT network composition for their performance.KEYWORDS single-walled carbon nanotubes, networks, charge transport, charge modulation spectroscopy, photoluminescence, trionSemiconducting single-walled carbon nanotubes (SWCNTs) have emerged as a promising material for future electronic applications as they combine high charge carrier mobilities with mechanical flexibility and solution-processability. 1, 2 Stimulated by the major progress in sorting techniques such as gel chromatography, 3, 4 density gradient ultracentrifugation, 5 aqueous two-phase separation, 6 and polymer-wrapping, 7-9 the reproducible fabrication of highperformance field-effect transistors (FETs) and circuits based on networks of purely semiconducting SWCNTs has become feasible. [10][11][12][13][14][15][16] Nonetheless, charge transport in nanotube networks is not yet fully understood especially regarding mixed networks of nanotube species with varying compositions. 17, 18 A detailed understanding of the fundamental transport parameters is necessary to further optimize effective carrier mobilities for competitive network devices at a minimum cost for purification.Charge transport in semiconductors is commonly studied through temperature-dependent measurements of conductivities and carrier mobilities. 17, 19-21 However, these techniques cannot distinguish between different SWCNT species and thus are not suitable to examine the chirality-dependent contributions to the macroscopic device performance. Given the high sensitivity of SWCNT absorption and emission features to charge carriers, which was shown in several studies, 22-25 electro-optical methods could provide additional and even chiralityspecific insights. For example, based on the analysis of the E11 absorption band change of...

Organic electrochemical transistors (ECTs) are an important building block for bioelectronics. To promote the required ion transport through the active layer, state-of-the-art semiconducting polymers feature hydrophilic ethylene glycol side chains that increase the volumetric capacitance and transconductance of the devices. Here, we apply this concept to polymer-wrapped single-walled carbon nanotubes (SWCNTs) as a high-mobility semiconducting material. We replace the polyfluorene copolymer (PFO-BPy), which is used for selectively dispersing semiconducting (6,5) SWCNTs and contains octyl side chains, by an equivalent polymer with tetraethylene glycol side chains. Aerosol-jet printed networks of these SWCNTs are applied as the active layer in water-gated ECTs. These show high hole mobilities (3−15 cm 2 •V −1 •s −1 ), significantly improved volumetric capacitances and larger transconductances. Thin networks of SWCNTs reach (219 ± 16) F•cm −1 •V −1 •s −1 as the product of mobility and volumetric capacitance. In situ photoluminescence measurements show more efficient quenching of the near-infrared fluorescence for nanotube networks with hydrophilic glycol side chains compared to those with hydrophobic alkyl side chains, thus corroborating more complete charging under bias. Overall, networks of semiconducting SWCNTs with such tailored wrapping polymers provide excellent device performance. Combined with their inherent mechanical flexibility and durability, they constitute a competitive material for bioelectronics.

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