Thermal rectification on asymmetric suspended graphene nanomesh devices

The graphene-based thermal rectification is investigated by measuring the thermal transport properties on asymmetric suspended graphene nanomesh devices. Sub-10 nm periodic nanopore phononic crystal structure is successfully patterned on the half area of the suspended graphene by the helium ion beam milling technology. The “differential thermal leakage” method is developed for thermal transport measurement without being disturbed by the electron current leakage through the suspended graphene bridge. Up to 60 % thermal rectification ratio is observed in a typical device with a nanopore pitch of 20 nm. By increasing the nanopore pitch in a particular range, the thermal rectification ratio shows an increment. However, this ratio is degraded by increasing the environmental temperature. This experiment preliminary shows a promising way to develop a high-performance thermal rectifier by using a phononic crystal to introduce the asymmetry on homogenous material.

Thermal diode based on a multilayer structure of phase change materials

Thermal diodes are devices that allow heat to flow preferentially in one direction. This unique thermal management capability has attracted attention in various applications, like electronics, sensors, energy conversion or space applications, among others. Despite their interest, the development of efficient thermal diodes remains still a challenge. In this paper, we report a scalable and adjustable thermal diode based on a multilayer structure that consists of a combination of phase change and phase invariant materials. We applied a parametric sweep in order to find the optimum conditions to maximize the thermal rectification ratio. Our simulations predicted a maximum thermal rectification ratio of ~20%. To evaluate the impact of these devices in real applications, we theoretically analysed the performance of a magnetocaloric refrigerating device that integrates this thermal diode. The results showed a 0.18 K temperature span between the heat source and the heat sink at an operating frequency of 25 Hz.

Investigation of transport behavior in borospherene-based molecular wire for rectification applications

The transport properties of molecular wire comprising of B40 fullerene are investigated by employing density functional theory (DFT) and non-equilibrium green’s function (NEGF) methodology. The quantum transport is evaluated by calculating the density of states, transmission spectra at various bias voltages, molecular energy spectra, HOMO-LUMO gap, current–voltage curve, and transmission pathways. In context to its properties, results show that by increasing the length of molecular wire, the device exhibits rectification ratio and prominent NDR behavior. I–V curve scrutinizes that as the length of wire is increased the curve becomes non-linear. This non-linear behavior is more prominent in the case when the length of wire is increased up to six fullerene cages significant rectification ratio (R.R) and negative differential resistance (NDR) comes into the picture. The excellent negative differential resistance ensures that a device with at least six molecular wires can be used as a tunnel diode. Graphic abstract

High Rectification Ratio in Polymer Diode Rectifier through Interface Engineering with Self-Assembled Monolayer

In this work, we demonstrate P3HT (poly 3-hexylthiophene) organic rectifier diode both in rigid and flexible substrate with a rectification ratio up to 106. This performance has been achieved through tuning the work function of gold with a self-assembled monolayer of 2,3,4,5,6-pentafluorobenzenethiol (PFBT). The diode fabricated on flexible paper substrate shows a very good electrical stability under bending tests and the frequency response is estimated at more than 20 MHz which is sufficient for radio frequency identification (RFID) applications. It is also shown that the low operating voltage of this diode can be a real advantage for use in a rectenna for energy harvesting systems. Simulations of the diode structure show that it can be used at GSM and Wi-Fi frequencies if the diode capacitance is reduced to a few pF and its series resistance to a few hundred ohms. Under these conditions, the DC voltages generated by the rectenna can reach a value up to 1 V.

Elucidating Multiple Negative Differential Resistance and Rectification Ratio Through L-Aspartic Acid at Nanometre Scale Using Symmetrical Metal Electrodes

Protein-based electronics is one of the growing areas of bio-nanoelectronics, where novel electronic devices possessing distinctive properties, are being fabricated using specific proteins. Furthermore, if the bio-molecule is analysed amidst different electrodes, intriguing properties are elucidated. This research article investigates the electron transport properties of L-aspartic acid (i.e., L-amino acid) bound to symmetrical electrodes of gold, silver, copper, platinum and palladium employing NEGF-DFT approach using self-consistent function. The theoretical work function of different electrodes is calculated using local density approximation and generalized gradient approximation approach. The calculated work function correlates well with the hole tunnelling barrier and conductance of the molecular device, which further authenticate the coupling strength between molecule and electrode. Molecule under consideration also exhibits the multiple negative differential resistance and rectification ratio with all the different electrodes, due to its asymmetrical structure. The molecular device using platinum electrodes exhibits the highest peak to valley ratio of 1.38 and rectification ratio of 3.20, at finite bias. The switching characteristics of different molecular device are justified with detailed transmission spectra and MPSH. These results indicate that L-aspartic acid and similar biomolecule can be vital to the growth of Proteotronics.

Characteristics and Electronic Band Alignment of a Transparent p-CuI/n-SiZnSnO Heterojunction Diode with a High Rectification Ratio

Transparent p-CuI/n-SiZnSnO (SZTO) heterojunction diodes are successfully fabricated by thermal evaporation of a (111) oriented p-CuI polycrystalline film on top of an amorphous n-SZTO film grown by the RF magnetron sputtering method. A nitrogen annealing process reduces ionized impurity scattering dominantly incurred by Cu vacancy and structural defects at the grain boundaries in the CuI film to result in improved diode performance; the current rectification ratio estimated at ±2 V is enhanced from ≈106 to ≈107. Various diode parameters, including ideality factor, reverse saturation current, offset current, series resistance, and parallel resistance, are estimated based on the Shockley diode equation. An energy band diagram exhibiting the type-II band alignment is proposed to explain the diode characteristics. The present p-CuI/n-SZTO diode can be a promising building block for constructing useful optoelectronic components such as a light-emitting diode and a UV photodetector.

Pengaruh Beban dan Filter pada Penyearah AC-DC Terkendali untuk Rangkaian Pengisi Li-ion Berbasis Bridge Rectifier dan Buck Converter Menggunakan Metode CC/CV

Saat ini, banyak perangkat elektronik yang menggunakan baterai sebagai sumber dayanya seperti handphone dan laptop. Sebuah charger baterai yang bersumber AC (Alternating Current) memiliki sebuah penyearah AC ke DC (Direct Current). Keluaran penyearah AC-DC tidak sesuai untuk pengisian CC/CV (Constant Current/Constant Voltage), sehingga diperlukan buck converter untuk menghasilkan nilai yang diinginkan. Selain itu, penyearahan AC-DC membawa ripple yang dapat merusak baterai dan mempengaruhi rectification ratio (RR), sehingga memerlukan filter untuk mengurangi ripple dan meningkatkan rectification ratio. Percobaan dilakukan pada kondisi arus konstan atau CC 1,5A dan kondisi tegangan konstan atau CV 4,2V menggunakan variasi beban. Pada percobaan CC, diketahui bahwa peningkatan beban akan menyebabkan peningkatan duty cycle yang dibutuhkan. Pada uji coba CV, diperoleh hasil bahwa peningkatan beban menyebabkan pengurangan duty cycle yang dibutuhkan. Penggunaan filter pada kondisi CC dan CV dapat mengurangi ripple dan meningkatkan RR. Pada kondisi CC, ripple matematis, simulasi, dan uji coba secara berturut-turut berkurang 46,45%, 46,43%, dan 45,46%. RR matematis, simulasi, dan uji coba secara berturut-turut meningkat 18,17%, 18,17%, dan 21,59%. Pada kondisi CV, ripple matematis, simulasi, dan uji coba secara berturut-turut berkurang 46,44%, 46,6%, dan 48,78%. RR matematis, simulasi, dan uji coba secara berturut-turut meningkat 18,17%, 18,17%, dan 20,99%. Pengisian Li-ion 3Ah memakan waktu 4 jam 58 detik. Dimana pengisian CC selama 32 menit 10 detik dan pengisian CV selama 3 jam 28 menit 48 detik. Pada pengisian CC duty cycle meningkat saat terjadinya peningkatan tegangan baterai. Sedangkan pada pengisian CV, duty cycle menurun saat berkurangnya arus pengisian.

Tunable solid-state thermal rectification by asymmetric nonlinear radiation

The tunable solid-state thermal rectification of a three-terminal device is presented by asymmetric nonlinear far-field radiation. The experimental findings are supplemented with finite element analysis, with a maximum rectification ratio of 93.1%.