Establishing Self-Dopant Design Principles from Structure-Function Relationships in Self-n-Doped Perylene Diimide Organic Semiconductors.

Self-doping is a particular doping method that has been applied to a wide range of organic semiconductors. However, there is a lack of understanding regarding the relationship between dopant structure and function. A structurally diverse series of self-n-doped perylene diimides (PDIs) is investigated to study the impact of steric encumbrance, counterion selection, and dopant/PDI tether distance on functional parameters such as doping, stability, morphology, and charge-carrier mobility.

Long-range charge carrier mobility in metal halide perovskite thin-films and single crystals via transient photo-conductivity.

Charge carrier mobility is a fundamental property of semiconductor materials that governs many electronic device characteristics. For metal halide perovskites, a wide range of charge carrier mobilities have been reported using different techniques. Mobilities are often estimated via transient methods assuming an initial charge carrier population after pulsed photoexcitation and measurement of photoconductivity via non-contact or contact techniques.

A piperidinium salt stabilizes efficient metal-halide perovskite solar cells.

Longevity has been a long-standing concern for hybrid perovskite photovoltaics. We demonstrate high-resilience positive-intrinsic-negative perovskite solar cells by incorporating a piperidinium-based ionic compound into the formamidinium-cesium lead-trihalide perovskite absorber. With the bandgap tuned to be well suited for perovskite-on-silicon tandem cells, this piperidinium additive enhances the open-circuit voltage and cell efficiency.

Impact of Moisture on Mobility in Methylammonium Lead Iodide and Formamidinium Lead Iodide.

The greatest remaining barrier to the commercialization of perovskite solar cells is their instability to ambient environmental conditions. While most studies of the electronic stability of perovskites employ finished devices, we here exploit the contactless characterization technique time-resolved microwave conductivity to probe electronic properties in the absence of encapsulation and interface effects. By tracking the mobility of charge carriers in two archetypal perovskite compounds, methylammonium lead iodide (MAPbI) and formamidinium lead iodide (FAPbI) under various conditions, we are able to make decisive statements about the role of water in the electronic performance of perovskites.

Publisher Correction: Deciphering photocarrier dynamics for tuneable high-performance perovskite-organic semiconductor heterojunction phototransistors.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Deciphering photocarrier dynamics for tuneable high-performance perovskite-organic semiconductor heterojunction phototransistors.

Looking beyond energy harvesting, metal-halide perovskites offer great opportunities to revolutionise large-area photodetection technologies due to their high absorption coefficients, long diffusion lengths, low trap densities and simple processability. However, successful extraction of photocarriers from perovskites and their conversion to electrical signals remain challenging due to the interdependency of photogain and dark current density. Here we report hybrid hetero-phototransistors by integrating perovskites with organic semiconductor transistor channels to form either "straddling-gap" type-I or "staggered-gap" type-II heterojunctions.

Main-Group Halide Semiconductors Derived from Perovskite: Distinguishing Chemical, Structural, and Electronic Aspects.

Main-group halide perovskites have generated much excitement of late because of their remarkable optoelectronic properties, ease of preparation, and abundant constituent elements, but these curious and promising materials differ in important respects from traditional semiconductors. The distinguishing chemical, structural, and electronic features of these materials present the key to understanding the origins of the optoelectronic performance of the well-studied hybrid organic-inorganic lead halides and provide a starting point for the design and preparation of new functional materials. Here we review and discuss these distinguishing features, among them a defect-tolerant electronic structure, proximal lattice instabilities, labile defect migration, and, in the case of hybrid perovskites, disordered molecular cations.

Mono- and Mixed-Valence Tetrathiafulvalene Semiconductors (TTF)BiI and (TTF)BiI with 1D and 0D Bismuth-Iodide Networks.

Two new compounds containing tetrathiafulvalene (TTF) cations with extended and discrete anions based on Bi and I are reported. The compound (TTF)BiI comprises [BiII] chains of edge-shared octahedra that are interspersed with stacks of TTF. The compound (TTF)BiI has mixed-valence stacks of TTF and TTF and discrete molecules of TTF separated by discrete [BiI] anions.

Infinite Polyiodide Chains in the Pyrroloperylene-Iodine Complex: Insights into the Starch-Iodine and Perylene-Iodine Complexes.

We report the preparation and X-ray crystallographic characterization of the first crystalline homoatomic polymer chain, which is part of a semiconducting pyrroloperylene-iodine complex. The crystal structure contains infinite polyiodide I∞ (δ-) . Interestingly, the structure of iodine within the insoluble, blue starch-iodine complex has long remained elusive, but has been speculated as having infinite chains of iodine.

Temperature-Dependent Polarization in Field-Effect Transport and Photovoltaic Measurements of Methylammonium Lead Iodide.

While recent improvements in the reported peak power conversion efficiency (PCE) of hybrid organic-inorganic perovskite solar cells have been truly astonishing, there are many fundamental questions about the electronic behavior of these materials. Here we have studied a set of electronic devices employing methylammonium lead iodide ((MA)PbI3) as the active material and conducted a series of temperature-dependent measurements. Field-effect transistor, capacitor, and photovoltaic cell measurements all reveal behavior consistent with substantial and strongly temperature-dependent polarization susceptibility in (MA)PbI3 at temporal and spatial scales that significantly impact functional behavior.

Exploring Two-Dimensional Transport Phenomena in Metal Oxide Heterointerfaces for Next-Generation, High-Performance, Thin-Film Transistor Technologies.

In the last decade, metal oxides have emerged as a fascinating class of electronic material, exhibiting a wide range of unique and technologically relevant characteristics. For example, thin-film transistors formed from amorphous or polycrystalline metal oxide semiconductors offer the promise of low-cost, large-area, and flexible electronics, exhibiting performances comparable to or in excess of incumbent silicon-based technologies. Atomically flat interfaces between otherwise insulating or semiconducting complex oxides, are also found to be highly conducting, displaying 2-dimensional (2D) charge transport properties, strong correlations, and even superconductivity.

Correlating Non-Geminate Recombination with Film Structure: A Comparison of Polythiophene: Fullerene Bilayer and Blend Films.

The morphology of the active layer in polymer:fullerene solar cells is a key parameter in determining their performance. In this study we monitor the charge carrier dynamics in bilayers of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) (fabricated by sequential spin coating and vacuum deposition) before and after thermal annealing, and compare these against conventional solution processed bulk heterojunction (BHJ) blend films. Transmission electron microscopy images, supported by field effect mobility data show that while not-annealed P3HT/PC61BM bilayers possess a sharp interface, intermixing proceeds upon annealing.

High Electron Mobility Thin-Film Transistors Based on Solution-Processed Semiconducting Metal Oxide Heterojunctions and Quasi-Superlattices.

High mobility thin-film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin-film transistors is reported that exploits the enhanced electron transport properties of low-dimensional polycrystalline heterojunctions and quasi-superlattices (QSLs) consisting of alternating layers of InO, GaO and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180-200 °C). Optimized prototype QSL transistors exhibit band-like transport with electron mobilities approximately a tenfold greater (25-45 cm V s) than single oxide devices (typically 2-5 cm V s).

Synthesis and characterization of fused pyrrolo[3,2-d:4,5-d']bisthiazole-containing polymers.

The synthesis of a novel electron-deficient fused pyrrolo[3,2-d:4,5-d']bisthiazole is reported from 2-bromothiazole. This was copolymerized with thiophene, selenophene, thienothiophene, and bithiophene by microwave-assisted Stille polycondensation. The resulting polymers exhibited small optical band gaps combined with low-lying HOMO energy levels and demonstrated semiconducting behavior in organic field effect transistors.