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Colloidal quantum dots (CQDs) are finding increasing applications in optoelectronic devices, such as photodetectors and solar cells, because of their high material quality, unique and attractive properties, and process flexibility without the constraints of lattice match and thermal budget. However, there is no adequate device model for colloidal quantum dot heterojunctions, and the popular Shockley-Quiesser diode model does not capture the underlying physics of CQD junctions. Here, we develop a compact, easy-to-use model for CQD devices rooted in physics. We show how quantum dot properties, QD ligand binding, and the heterointerface between quantum dots and the electron transport layer (ETL) affect device behaviors. We also show that the model can be simplified to a Shockley-like equation with analytical approximate expressions for reverse saturation current, ideality factor, and quantum efficiency. Our model agrees well with the experiment and can be used to describe and optimize CQD device performance.

High-sensitivity room-temperature multi-dimensional infrared (IR) detection is crucial for military and civilian purposes. Recently, the gapless electronic structures and unique optoelectrical properties have made the two-dimensional (2D) topological semimetals promising candidates for the realization of multifunctional optoelectronic devices. Here, we demonstrated the in-situ construction of high-performance 1T'-MoTe2/Ge Schottky junction device by inserting an ultrathin AlOx passivation layer. The good detection performance with an ultra-broadband detection wavelength range of up to 10.6 micron, an ultrafast response time of ~ 160 ns, and a large specific detectivity of over 109 Jones in mid-infrared (MIR) range surpasses that of most 2D materials-based IR sensors, approaching the performance of commercial IR photodiodes. The on-chip integrated device arrays with 64 functional detectors feature high-resolution imaging capability at room temperature. All these outstanding detection features have enabled the demonstration of position-sensitive detection applications. It demonstrates an exceptional position sensitivity of 14.9 mV/mm, an outstanding nonlinearity of 6.44%, and commendable trajectory tracking and optoelectronic demodulation capabilities. This study not only offers a promising route towards room-temperature MIR optoelectronic applications, but also demonstrates a great potential for application in optical sensing systems. [ABSTRACT FROM AUTHOR]

Transcranial magnetic stimulation has been gaining popularity in the therapy for several neurological disorders. A time-varying magnetic field is used to generate electric field in the brain. As the development of TMS methods takes place, emphasis on the coil design increases in order to improve focal stimulation. Ideally reduction of stimulation of neighboring regions of the target area is desired. This study, focused on the improvement of the focality of the Quadruple Butterfly Coil (QBC) with supplemental use of different passive shields. Parameters such as shape, position and permeability of the shields have been explored to improve the focus of stimulation. Results have been obtained with the help of computer modelling of a MRI derived heterogeneous head model over the vertex position and the dorsolateral prefrontal cortex position using a finite element tool. Variables such as maximum electric field induced on the grey matter and scalp, volume and area of stimulation above half of the maximum value of electric field on the grey matter, and ratio of the maximum electric field in the brain versus the scalp have been investigated. [ABSTRACT FROM AUTHOR]