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Structural and electronic properties simulated using DFT/PBE level of theory with TS dispersion correction as implemented in FHI-Aims code.

One-dimensional perovskites occupy an important place among modern semiconducting materials, offering design flexibility together with a wide range of properties. However, most such materials have a large bandgap, which limits their application in photovoltaics. Here, we present a new one-dimensional hybrid perovskite containing the functional cation aminophenyl viologen (APhV). Similar to other materials from the viologen perovskite family, aminophenyl viologen iodidoplumbate(II) APhV[Pb2I6]∙2NMP) exhibits a broad absorption with a narrow and direct bandgap of 1.66 eV, which was calculated from the experimental data and is supported also by our first-principles simulations. Close contact between electron-rich inorganic chains and electron-accepting viologen molecules suggests charge transfer within the hybrid, also visible in the density of states. Considering its reasonable thermal stability, aminophenyl viologen iodidoplumbate can find a wide application in photovoltaics.

Hybrid organic–inorganic lead halide perovskites have drawn much interest due to their optical and electronic properties. The ability to fine-tune the structure by the organic component allows for obtaining a wide range of materials with various dimensionalities. Here, we combine experimental and theoretical work to investigate the structures and properties of a series of low-dimensional hybrid organic–inorganic perovskites, based on naphthalene ammonium cations, 2,6-diaminonaphthalene (2,6-DAN), 1-aminonaphthalene (1-AN) and 2-aminonaphthalene (2-AN). All materials exhibit edge- or face-sharing 1D chain structures. Compared to the 2D counterpart containing isomeric 1,5-diaminonaphthalene (1,5-DAN), 1D hybrid materials exhibit broadband light emission arising from the self-trapped excitons (STEs) owing to their highly distorted structure. This work expands the library of low-dimensional hybrid perovskites and opens new possibilities for obtaining broadband-light-emitting materials.

A pair of hole-conducting polymers comprising 3,6-linked carbazole and meta-linked anisole derivatives having solubilizing moieties to enable their solution processability, and complementarily reactive side-groups (azide and alkyne) for cross-linking, are synthesized and characterized. The polymers can be cross-linked either by thermal annealing at relatively low temperatures in the 85–110 °C range, or by UV irradiation. A general applicability of the latter for a photolithographic patterning of the hole conducting polymer is proven. The polymers have an ionization potential (IP) of 5.8 eV, close to the IP of a small molecule hole-conductor tris(4-carbazoyl-9-ylphenyl)amine (TCTA). In combination with a strong dopant hexacyano-trimethylene-cyclopropane (CN6CP), but not with commercial 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), the polymers can be efficiently p-doped to increase their conductivity by 5–6 orders of magnitude, as measured in devices with a lateral setup. Taken together, these characteristics suggest that the synthesized polymers are promising candidates for their use in solution-processable organic light-emitting diodes as hole-injection layer and hole-transporting layer materials, which will be verified in the upcoming work. © 2022 The Authors. Advanced Materials Interfaces published by Wiley-VCH GmbH.

Diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP-based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (ECT) of the blend films lies exceptionally close to the singlet energy of the donor (ED*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (VOC) is therefore determined to be due to rather high nonradiative (≈ 418 ± 13 mV) and unavoidable radiative voltage losses (≈ 255 ± 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (JSC) covers a vast span from 7 to 18 mA cm-2 for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.

We investigate the conductance of optimized donor-acceptor-donor molecular wires obtained by on-surface synthesis on the Au(111) surface. A careful balance between acceptors and donors is achieved using a diketopyrrolopyrrole acceptor and two thiophene donors per unit along the wire. Scanning tunneling microscopy imaging, spectroscopy, and conductance measurements done by pulling a single molecular wire at one end are presented. We show that the conductance of the obtained wires is among the highest reported so far in a tunneling transport regime, with an inverse decay length of 0.17 Å-1. Using complex band structure calculations, different donor and acceptor groups are discussed, showing how a balanced combination of donor and acceptor units along the wire can further minimize the decay of the tunneling current with length.