Encapsulate-and-peel: fabricating carbon nanotube CMOS integrated circuits in a flexible ultra-thin plastic film

Fabrication of single-walled carbon nanotube thin film (SWNT-TF) based integrated circuits (ICs) on soft substrates has been challenging due to several processing-related obstacles, such as printed/transferred SWNT-TF pattern and electrode alignment, electrical pad/channel material/dielectric layer flatness, adherence of the circuits onto the soft substrates etc. Here, we report a new approach that circumvents these challenges by encapsulating pre-formed SWNT-TF-ICs on hard substrates into polyimide (PI) and peeling them off to form flexible ICs on a large scale. The flexible SWNT-TF-ICs show promising performance comparable to those circuits formed on hard substrates. The flexible p- and n-type SWNT-TF transistors have an average mobility of around 60 cm(2) V-1 s(-1), a subthreshold slope as low as 150 mV dec(-1), operating gate voltages less than 2 V, on/off ratios larger than 10(4) and a switching speed of several kilohertz. The post-transfer technique described here is not only a simple and cost-effective pathway to realize scalable flexible ICs, but also a feasible method to fabricate flexible displays, sensors and solar cells etc

A further comparison of graphene and thin metal layers for plasmonics

Which one is much more suitable for plasmonic materials, graphene or metal? To address this problem well, the plasmonic properties of thin metal sheets at different thicknesses have been investigated and compared with a graphene layer. As demonstration examples, the propagation properties of insulatormetal-insulator and metamaterials (MMs) structures are also shown. The results manifest that the plasmonic properties of the graphene layer are comparable to that of thin metal sheets with the thickness of tens of nanometers. For the graphene MMs structure, by using the periodic stack structure in the active region, the resonant transmission strength significantly improves. At the optimum period number, 3-5 periods of graphene/SiO2, the graphene MMs structure manifests good frequency and amplitude tunable properties simultaneously, and the resonant strength is also strong with large values of the Q-factor. Therefore, graphene is a good tunable plasmonic material. The results are very helpful to develop novel graphene plasmonic devices, such as modulators, antenna and filters

16% efficient silicon/organic heterojunction solar cells using narrow band-gap conjugated polyelectrolytes based low resistance electron-selective contacts

Dopant-free silicon (Si)/organic heterojunction solar cells (HSCs) have drawn much attention due to their immense potential in achieving high power conversion efficiencies (PCEs) with simple device architectures and fabrication procedures. However, unsatisfied rear-contacts severely hinder further improvement in PCEs for these promising HSCs. Exploring effective cathodic interfacial materials with low temperature fabrication to replace conventional diffusion layer shows the extremely importance of technical innovation. Here, poly[4,8-bis (2-ethylhexyloxyl)benzo[1,2-b: 4,5-b']dithiophene-2,6-diyl-alt-ethylhexyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate-4,6-diyl] (PTB7)-based narrow band-gap conjugated polyelectrolytes, PTB7-NBr and PTB7-NSO3, are firstly employed as effective cathodic interfacial materials in Si/organic HSCs to improve the passivation and electron transporting property at n-Si/Al interface. The low-temperature proceeded electron-selective contact of n-Si/PTB7-NBr/Al gives a contact resistivity as low as 6.7 +/- 0.8 m Omega cm(2), upon it a remarkable PCE of 16.0% is finally obtained from a completely dopant-free Si/organic HSC. The understanding of conjugated polyelectrolytes on interfacial modification may lead a path to fabricate high performance Si/organic heterojunction devices with efficient charge transfer process at a simplified fabrication process

Improvement on the Si/PEDOT:PSS hybrid solar cells by rear-sided passivation with SiNx:H layers

A patterned silicon nitride (SiNx:H) passivation layer was employed to improve the performance of silicon/poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (Si/PEDOT:PSS) hybrid solar cells, achieving of an enhancement in the power conversion efficiency (PCE) of 0.6%. The insertion of patterned SiNx:H layer with a 80% SiNx:H-to-substrate ratio boosted the open circuit voltage (V-oc) from 523.1 mV to 573.4 mV, suggesting the well-passivation property of the patterned SiNx:H thin layer that was created by plasma enhanced chemical vapor deposition and lithography processes

Over 16.7% Efficiency Organic-Silicon Heterojunction Solar Cells with Solution-Processed Dopant-Free Contacts for Both Polarities

Realization of synchronous improvement in optical management and electrical engineering is necessary to achieve high-performance photovoltaic device. However, inherent challenges are faced in organic-silicon heterojunction solar cells (HSCs) due to the poor contact property of polymer on structured silicon surface. Herein, a remarkable efficiency boost from 12.6% to over 16.7% in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/n-silicon (PEDOT:PSS/n-Si) HSCs by independent optimization of hole-/electron-selective contacts only relying on solution-based processes is realized. A bilayer PEDOT:PSS film with different functionalizations is utilized to synchronously realize conformal contact and effective carrier collection on textured Si surface, making the photogenerated carriers be well separated at heterojunction interface. Meanwhile, fullerene derivative is used as electron-transporting layer at the rear n-Si/Al interface to reduce the contact barrier. The study of carriers' transport and independent optimization on separately contacted layers may lead to an effective and simplified path to fabricate high-performance organic-silicon heterojunction devices

Metal–Organic Frameworks–Based Memristors: Materials, Devices, and Applications

Facing the explosive growth of data, a number of new micro-nano devices with simple structure, low power consumption, and size scalability have emerged in recent years, such as neuromorphic computing based on memristor. The selection of resistive switching layer materials is extremely important for fabricating of high performance memristors. As an organic-inorganic hybrid material, metal-organic frameworks (MOFs) have the advantages of both inorganic and organic materials, which makes the memristors using it as a resistive switching layer show the characteristics of fast erasing speed, outstanding cycling stability, conspicuous mechanical flexibility, good biocompatibility, etc. Herein, the recent advances of MOFs-based memristors in materials, devices, and applications are summarized, especially the potential applications of MOFs-based memristors in data storage and neuromorphic computing. There also are discussions and analyses of the challenges of the current research to provide valuable insights for the development of MOFs-based memristors

Scattering effect of the high-index dielectric nanospheres for high performance hydrogenated amorphous silicon thin-film solar cells

Dielectric nanosphere arrays are considered as promising light-trapping designs with the capability of transforming the freely propagated sunlight into guided modes. This kinds of designs are especially beneficial to the ultrathin hydrogenated amorphous silicon (a-Si:H) solar cells due to the advantages of using lossless material and easily scalable assembly. In this paper, we demonstrate numerically that the front-sided integration of high-index subwavelength titanium dioxide (TiO2) nanosphere arrays can significantly enhance the light absorption in 100 nm-thick a-Si:H thin films and thus the power conversion efficiencies (PCEs) of related solar cells. The main reason behind is firmly attributed to the strong scattering effect excited by TiO2 nanospheres in the whole waveband, which contributes to coupling the light into a-Si: H layer via two typical ways: 1) in the short-waveband, the forward scattering of TiO2 nanospheres excite the Mie resonance, which focuses the light into the surface of the a-Si:H layer and thus provides a leaky channel; 2) in the long-waveband, the transverse waveguided modes caused by powerful scattering effectively couple the light into almost the whole active layer. Moreover, the finite-element simulations demonstrate that photocurrent density (J(ph)) can be up to 15.01 mA/cm(2), which is 48.76% higher than that of flat system

A bifunctional catalyst of ultrathin cobalt selenide nanosheets for plastic-electroreforming-assisted green hydrogen generation

Despite the tremendous advances of electrocatalysts for the hydrogen and oxygen evolution reactions (HER/OER), there are few reports on bifunctional catalysts for the HER and plastic electroreforming. Herein, we present a facile hydrothermal and selenization treatment to fabricate cobalt selenide nanosheets on nickel foam (0.1-CoSe2/NF) as a bifunctional catalyst for plastic-electroreforming assisted water electrolysis. Benefiting from its large specific surface area, abundant active sites, high conductivity and 3D porous structure, 0.1-CoSe2/NF exhibits superior electrocatalytic performance and durability for both the HER and electrooxidation of plastic waste polylactic acid (PLA). Overpotentials of 202 mV (cathodic) and 288 mV (anodic) are observed at a current density of 100 mA cm−2 in an alkaline electrolyte. Moreover, PLA oxidation that suppresses the OER also addresses the safety concern of gas crossover in water electrolysis. Our work thus provides a promising pathway for low-cost, high efficiency, and stable production of green hydrogen assisted by electroreforming of plastic waste.Nanyang Technological UniversitySubmitted/Accepted versionThis work was supported by Nanyang Technological University (Grant No. NTU-ACE2021-02)