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Semiconductors, featuring tunable electrical transport, and magnets, featuring tunable spin configurations, form the basis of many information technologies. A long-standing challenge has been to realize materials that integrate and connect these two distinct properties. Two-dimensional (2D) materials offer a platform to realize this concept, but known 2D magnetic semiconductors are electrically insulating in their magnetic phase. Here we demonstrate tunable electron transport within the magnetic phase of the 2D semiconductor CrSBr and reveal strong coupling between its magnetic order and charge transport. This provides an opportunity to characterize the layer-dependent magnetic order of CrSBr down to the monolayer via magnetotransport. Exploiting the sensitivity of magnetoresistance to magnetic order, we uncover a second regime characterized by coupling between charge carriers and magnetic defects. The magnetoresistance within this regime can be dynamically and reversibly tuned by varying the carrier concentration using an electrostatic gate, providing a mechanism for controlling charge transport in 2D magnets., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.

Though both the crystal structure and molecular orientation of organic semiconductors are known to impact charge transport in thin-film devices, separately accessing different polymorphs and varying the out-of-plane molecular orientation is challenging, typically requiring stringent control over film deposition conditions, film thickness, and substrate chemistry. Here we demonstrate independent tuning of the crystalline polymorph and molecular orientation in thin films of contorted hexabenzocoronene, c-HBC, during post-deposition processing without the need to adjust deposition conditions. Three polymorphs are observed, two of which have not been previously reported. Using our ability to independently tune the crystal structure and out-of-plane molecular orientation in thin films of c-HBC, we have decoupled and evaluated the effects that molecular packing and orientation have on device performance in thin-film transistors (TFTs). In the case of TFTs comprising c-HBC, polymorphism and molecular orientation are equally important; independently changing either one affects the field-effect mobility by an order of magnitude.

We demonstrate an alternative path for achieving high-transconductance organic transistors by assembling bilayers of pentacene onto random arrays of single-walled carbon nanotubes. We show here that, by varying the connectivity of the underlying nanotube network, the channel length of a thin-film transistor can be reduced by nearly two orders of magnitude—thus, enabling the increase of the device transconductance without reduction the on/off ratio. These field-induced percolating networks enable assembling high-transconductance transistors that, with relatively large source drain distances, can be manufactured with available commercial printing techniques. [ABSTRACT FROM AUTHOR]

We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in mobility of the underlying organic semiconductor. The method is based on percolating networks, which we create from a dispersion of individual single-wall carbon nanotubes and narrow ropes within an organic semiconducting host. The majority of current paths between source and drain follow the metallic nanotubes but require a short, switchable semiconducting link to complete the circuit. With these nanotube-semiconducting composites we achieve effectively a 60× reduction in source to drain distance, which is equivalent to a 60-fold increase of the “effective” mobility of the starting semiconducting material with a minor decrease of the on/off current ratio. These field-induced percolating networks allow for the fabrication of high-transconductance transistors having relatively large source to drain distances that can be manufactured inexpensively by commercially available printing techniques. [ABSTRACT FROM AUTHOR]

Abstract: A new oligomer of bithiophene and substituted fluorene has been successfully synthesized, exhibiting good FET performance. Our results show that devices can be obtained from inkjetted OTFTs and elaborated by direct writing without any particular pre-patterning or self-alignment techniques. We have also demonstrated the possibility to fabricate inexpensive OTFTs by direct writing paving the way toward using inkjet printing as the key technology for such applications in plastic electronics. The ease of this technique allows charts a clear path to flexible electronics. [Copyright &y& Elsevier]

Abstract: We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The method is based on creating sub-percolating conducting networks either as a single layer composite or a bi-layer assembly. In the single layer composite, individual single wall carbon nanotubes (SWNT) and narrow ropes are dispersed in a soluble organic semiconducting host. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in mobility of the underlying organic semiconductor without reduction of the on/off ratio. In the semiconducting bi-layers pentacene is evaporated onto arrays of carbon nanotubes (SWNT) of varying connectivity. These field-induced sub-percolating networks allow an effective 10× reduction in source to drain distance that concurrent with a significant lowering in the pentacene crystallinity yields to a modest 2–5× increase in mobility without reduction in the on/off ratio. In both geometries, the majority of current paths between source and drain follow the metallic nanotubes but require a short, switchable semiconducting link to complete the circuit. [Copyright &y& Elsevier]