Eva M. Herzig

Organic mixed ionic‐electronic conductors (OMIECs) are key components for the next‐generation bioelectronics, albeit with n ‐type materials remaining significantly underrepresented compared to their p ‐type counterparts. Furthermore, reaching low operating voltages alongside high ambient and operational stability remains challenging when employing n ‐type OMIECs in organic electrochemical transistor (OECT)‐based applications. Herein, we report two novel n ‐type polymeric OMIECs, based on an azaisatin and benzodifurandione‐based backbone, incorporating either non‐fluorinated or fluorinated bithiophene donor units. The resulting polymers, obtained via Aldol polymerization, have high electron affinities of 4.5–4.7 eV. Both polymers function in n ‐type accumulation mode OECTs with indications of tunable antiambipolar behavior. The fluorinated polymer displays a low threshold voltage of 0.14 V, while the non‐fluorinated analogue offers excellent operational stability, with the OECT retaining 96% of its initial current after 1800 s of cycling.

Different synthesis parameters were studied influencing film thickness, aggregate formation, and pore ordering of ordered mesoporous silica thin film with vertically oriented pores.

This study reveals how the morphology of organic mixed ionic-electronic conductors (OMIECs) controls the mixed ionic-electronic transport of organic electrochemical transistors (OECTs). Two p-type OMIECs with oligoethylene glycol (OEG) side chains, namely P3MEEET and P3MEEMT, are blended with polystyrene (PS) to produce laterally phase-separated morphologies. By varying the ratio between OMIEC and PS, distinct morphologies are created via nucleation and growth and via spinodal decomposition. Furthermore, porous films are fabricated through the selective dissolution of PS, providing a direct comparison between blend and porous structures on OECT performance. In blends, the reduced ion injection area significantly enhances the mobility (μ) and figure of merit (μC^*). Due to the hydrophilic nature of the OMIECs, adding pores to the films does not have a positive effect on signal amplification but improves ion storage via side injection and increases the effective volumetric capacitance (C^*). Comparing the two OMIECs studied, porous samples based on P3MEEMT experience a greater benefit from electrolyte side injection. Both blend and porous samples are characterized using a range of techniques, including spectroelectrochemistry (SEC), atomic force microscopy (AFM), scanning transmission X-ray microscopy (STXM), quartz crystal microbalance (QCM), along with ex situ and in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) to unravel the mechanism of the mixed ionic-electronic transport from both an ionic and electronic perspective.

We report the first high-throughput Mg–Bi–O thin-film synthesis via combinatorial co-sputtering, revealing composition-dependent structural evolution and tunable bandgaps.

The electron-poor azaisoindigo motif, with amphiphilic side chains to facilitate ion interactions, is copolymerised with bithiophenes of varying electron-donating ability. The comonomer choice determines the dominant charge carrier species in OECTs.

The response surface methodology (RSM) based on a Box-Behnken (BB) design of experiment (DoE) approach was performed, with the central point repeated four times to enhance statistical reliability, to systematically investigate the influence of ultrasonic aerosol jet printing (uAJP) parameters such as speed, flow, and power, while depositing the donor material deposition, on the acceptor/donor ratio and power conversion efficiency (PCE). Efforts were made to tune the D:A ratio to approximately 1:1.2, a composition widely used for the PM6:Y12 active layer system. Despite the sequential deposition of the donor material onto the acceptor, the resulting active layer exhibited a bulk heterojunction (BHJ) morphology rather than a layer-by-layer (LbL) structure. Further analysis such as film-depth-dependent light absorption spectra (FLAS) and cross section of the electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) or STEM-EELS was used to explore the interplay between deposition parameters and vertical blending behavior in the active layer. Finally, we evaluated the stability of these OPV devices under continuous one-sun illumination for 1080 h, revealing that the most efficient devices also exhibited the highest operational stability.

In organic photovoltaics, even small morphological changes on the sub‐nanometer scale can significantly impact the device's performance. Such structural changes intrinsically occur due to the thermal response of a material, making a fundamental understanding of these processes essential. In this study, the thermal expansion of the high‐performance donor material PDBD‐T‐2F (PM6) is characterized using in situ transmission and grazing incidence wide‐angle X‐ray scattering (WAXS and GIWAXS) over the temperature range of 30–300 °C. By systematically increasing the complexity of the sample, multiple influencing factors are deciphered. Significantly, distinct structural differences and temperature expansion behavior is observed for the face‐on and edge‐on crystallite fraction. In particular, the initial lamellar stacking d ‐spacings differ for the two fractions and moreover, the face‐on fraction exhibits significantly lower thermal expansion in lamellar direction compared to the edge‐on fraction. In situ GIWAXS measurements performed during solution coating show that these differences are formed during film formation. Additionally, an impact of the thermal expansion mismatch between the substrate and the sample is observed, limiting the in‐plane π–π stacking expansion. The results emphasize the interplay between molecular packing, substrate interaction, and thermal response.

The solution‐based fabrication of reproducible, high‐quality lead iodide perovskite films demands a detailed understanding of the crystallization dynamics, which is mainly determined by the perovskite precursor solution and its processing conditions. A systematic in situ study is conducted during the critical phase before the nucleation in solution to elucidate the formation dynamics of lead iodide perovskite films. Using ultraviolet (UV) absorption spectroscopy during spin coating allows to track the evolution of iodoplumbate complexes present in the precursor solution. It is found that prior to film formation, a novel absorption signature at 3.15 eV arises. This is attributed to the emergence of a PbI ₂ ‐DMF solvated (PDS) phase. The amount of PDS phase is closely connected to the concentration of the solution layer during spin coating. It is also proposed that PDS clusters are a predecessor of crystalline perovskite phases and act as nucleation seeds in the precursor solution. In this way, this work provides insights into the early stages of perovskite crystallization.