Search results for "Heterojunction"

Two-Step Solution-Processed Two-Component Bilayer Phthalocyaninato Copper-Based Heterojunctions with Interesting Ambipolar Organic Transiting and Eth…

2016

International audience; The two-component phthalocyaninato copper-based heterojunctions fabricated from n-type CuPc(COOC8H17)(8) and p-type CuPc(OC8H17)(8) by a facile two-step solution-processing quasi-Langmuir-Shafer method with both n/p- and p/n-bilayer structures are revealed to exhibit typical ambipolar air-stable organic thin-film transistor (OTFT) performance. The p/n-bilayer devices constructed by depositing CuPc(COOC8H17)(8) film on CuPc(OC8H17)(8) sub-layer show superior OTFT performance with hole and electron mobility of 0.11 and 0.02 cm(2) V-1 s(-1), respectively, over the ones with n/p-bilayer heterojunction structure with the hole and electron mobility of 0.03 and 0.016 cm(2) …

The influence of Coulomb interaction screening on the excitons in disordered two-dimensional insulators.

2021

AbstractWe study the joint effect of disorder and Coulomb interaction screening on the exciton spectra in two-dimensional (2D) structures. These can be van der Waals structures or heterostructures of organic (polymeric) semiconductors as well as inorganic substances like transition metal dichalcogenides. We consider 2D screened hydrogenic problem with Rytova–Keldysh interaction by means of so-called fractional Scrödinger equation. Our main finding is that above synergy between screening and disorder either destroys the exciton (strong screening) or promote the creation of a bound state, leading to its collapse in the extreme case. Our second finding is energy levels crossing, i.e. the degen…

Synthesis of Graphene Nanoribbons by Ambient-Pressure Chemical Vapor Deposition and Device Integration

2016

Graphene nanoribbons (GNRs), quasi-one-dimensional graphene strips, have shown great potential for nanoscale electronics, optoelectronics, and photonics. Atomically precise GNRs can be "bottom-up" synthesized by surface-assisted assembly of molecular building blocks under ultra-high-vacuum conditions. However, large-scale and efficient synthesis of such GNRs at low cost remains a significant challenge. Here we report an efficient "bottom-up" chemical vapor deposition (CVD) process for inexpensive and high-throughput growth of structurally defined GNRs with varying structures under ambient-pressure conditions. The high quality of our CVD-grown GNRs is validated by a combination of different …

Indium surfactant effect on AlN/GaN heterostructures grown by metal-organic vapor-phase epitaxy: Applications to intersubband transitions

2006

We report on a dramatic improvement of the optical and structural properties of AlN/GaN multiple quantum wells (MQWs) grown by metal-organic vapor-phase epitaxy using indium as a surfactant. This improvement is observed using photoluminescence as well as x-ray diffraction. Atomic force microscopy shows different surface morphologies between samples grown with and without In. This is ascribed to a modified relaxation mechanism induced by different surface kinetics. These improved MQWs exhibit intersubband absorption at short wavelength (2 mu m). The absorption linewidth is as low as 65 meV and the absorption coefficient is increased by 85%.

Erratum to: Sub-gap defect density characterization of molybdenum oxide: An annealing study for solar cell applications

2022

Enhanced efficiency in plastic planar heterojunction solar cells by AuNPs positioned at donor-acceptor interfaces

2018

A new class of copolymers containing oligothiophene moieties with different length and fullerene units have been designed and prepared by an easy and inexpensive one-step synthetic approach. The incorporation of small quantities of these copolymers into bulk heterojunction (BHJ) solar cells with donor regioregular polythiophene (P3HT) and acceptor fullerene derivate (PCBM) results in a good control of the phase separation process without further affecting the BHJ optoelectronic properties. Indeed, these copolymers allow modulating under thermal annealing the growth of domains whose size depends on the length of the copolymer repetitive units. Domain size on the same length scale of the P3HT…

Metallization of Si heterojunction solar cell by Cu electroplating

2018

In response to recent climate change, many renewable energy solutions have acquired great importance; in fact, the need of sustainable development is increasing and the use of renewable energy, such as solar energy, can be applied to many industrial and consumer applications. Photovoltaic systems, which are made up of solar cells, are used for electrical vehicle charging stations and to supply remote areas not connected to the power distribution network; moreover, solar energy is widely used as a primary or secondary source of domestic electric power. In this scenario, the increasing in efficiency, and the cost reduction of solar cells, becomes a priority in the diffusion of PV systems for …

Blue-violet heterojunction LEDs based on hydrothermally synthesized ZnO nanorods

2016

Zinc oxide nanorods have great potential for the realization of high efficiency heterostructure LEDs based on p-doped GaN. Well-aligned vertical nanorods are desirable to enhance the LED outcoupling performances due to a better confinement of the light [1]. However, due to the lack of reproducible p-type ZnO, a p-GaN substrate is still needed. This work reports on the fabrication of n-ZnO/p-GaN heterojunction LEDs based on vertical ZnO nanorods grown by hydrothermal method. The chemical reaction in the hydrothermal growth of ZnO is based on the decomposition of zinc nitrate, (Zn(NO3)2) with resulting Zn2+ ions reacting with the hydroxyl ions obtained by the thermal degradation of hexamethyl…

Photoelectrochemical Characterization of Ta/Ta2O5/Polypyrrole Heterojunctions

2009

A photodeposition of polypyrrole on anodic tantalum oxide thin films was performed in both organic and aqueous media. Pyrrole was photo-oxidised on insulating tantalum oxide by irradiating the electrode with light of suitable energy. Tantalum/ tantalum oxide/ polypyrrole heterojunctions were then characterized by means of photocurrent spectroscopy. The comparison between the photoelectrochemical response of the heterojunctions fabricated in organic and aqueous media, shows that the solvent used for the photodeposition of polypyrrole influences the location of the inversion potential. This result can be attributed to the different structure of polypyrrole films, which strongly depends on the…

p -Type and n -type conductometric behaviors of octachloro-metallophthalocyanine-based heterojunctions, the key role of the metal

2020

In the present work, we determined the electrical properties of octachlorinated metallophthalocyanines with Co(II) and Cu(II) ions as metal centers. We engaged them in heterojunctions, with lutetium bisphthalocyanine as a partner. Surprisingly, cobalt and copper complexes show opposite behaviors, the first being an [Formula: see text]-type material whereas the latter is a [Formula: see text]-type material, as deduced from the response of the heterojunctions towards ammonia; showing the unusual key role played by the metal center. While the LuPc[Formula: see text]/Cu(Cl[Formula: see text]Pc) complex exhibits a negative response to ammonia, the LuPc[Formula: see text]/Co(Cl[Formula: see text…