Influence of chemical interactions on the electronic properties of BiOI/organic semiconductor heterojunctions for application in solution-processed electronics.

Bismuth oxide iodide (BiOI) has been viewed as a suitable environmentally-friendly alternative to lead-halide perovskites for low-cost (opto-)electronic applications such as photodetectors, phototransistors and sensors. To enable its incorporation in these devices in a convenient, scalable, and economical way, BiOI thin films were investigated as part of heterojunctions with various p-type organic semiconductors (OSCs) and tested in a field-effect transistor (FET) configuration. The hybrid heterojunctions, which combine the respective functionalities of BiOI and the OSCs were processed from solution under ambient atmosphere. The characteristics of each of these hybrid systems were correlated with the physical and chemical properties of the respective materials using a concept based on heteropolar chemical interactions at the interface. Systems suitable for application in lateral transport devices were identified and it was demonstrated how materials in the hybrids interact to provide improved and synergistic properties. These indentified heterojunction FETs are a first instance of successful incorporation of solution-processed BiOI thin films in a three-terminal device. They show a significant threshold voltage shift and retained carrier mobility compared to pristine OSC devices and open up possibilities for future optoelectronic applications.

Thiourea-Derived Single-Source Molecular Precursor For Spin-Coated PbS Thin Films.

In search of a suitable single-source precursor for the deposition of nanostructured PbS thin films at moderate temperatures under ambient conditions, we have synthesized the ligand N-(thiomorpholine-4-carbothioyl)benzamide and its corresponding lead(II) complex. The structures of both compounds were determined by single-crystal X-ray diffraction. In the complex, two ligands coordinate to a lead(II) atom in hemi-directed geometry through S and O atoms. Secondary intermolecular Pb⋅⋅⋅S interactions group the complexes into pairs. As bulk powders, both the ligand and complex show nominal composition and purity as evidenced by elemental analysis, 1 H NMR and IR spectroscopy. Thermal analysis of the lead(II) complex was carried out to understand its thermal decomposition behaviour for establishing a thin film fabrication protocol. Thin films of phase-pure PbS were fabricated using this new molecular precursor at the comparatively low annealing temperature of 250 °C. The film showed nanoparticles with cuboidal morphology and a blue-shifted optical absorption.

A copper(ii)-coordination polymer based on a sulfonic-carboxylic ligand exhibits high water-facilitated proton conductivity.

Proton conduction ability has been investigated in a new Cu(ii) based coordination polymer (CP), {[Cu2(sba)2(bpg)2(H2O)3]·5H2O}n (1), synthesized using the combination of 4-sulfobenzoic acid (4-Hsba) and bipyridine-glycoluril (BPG) ligands. Single crystal X-ray structure determination revealed that 1 features 1D porous channels encapsulating a continuous array of water molecules. Proton conductivity measurements reveal a high conductivity value of 0.94 × 10-2 S cm-1 at 80 °C and 95% RH. The activation energy (Ea) of 0.64 eV demonstrates that the solvate water, coordinated water and hydrophilic groups in the channels promote the mobility of protons in the framework. Water sorption measurements exhibited hysterical behaviour with a high uptake value of 379.07 cm3 g-1. Time-dependent measurements revealed that the proton conductivity is retained even after 12 h of measurements. The proton conduction mechanism was validated by ab initio electronic structure calculations using the Nudged Elastic Band (NEB) method with molecular dynamics (MD) simulation studies. The theoretical activation energy is calculated to be 0.54 eV which is in accordance with the experimental value.