We present a systematic study of the morphology and absorption properties of a typical donor–acceptor polymer (PCPDTBT) with semicrystalline behavior in solution and in thin films. In-situ ...spectroelectrochemical data give information about the evolution of the absorption spectra from neutral to charged species. The experimental data are supported by theoretical calculations in the framework of the density functional theory (DFT). Regarding thin film structures, we show that the choice of the solvent has significant influence on the morphology in thin films: whereas CS2 and CHCl3 give rather structureless (amorphous) morphologies, films from 1-CN exhibit a clear crystalline nanofiber morphology. Accompanying UV/vis/NIR spectra of films are highly dependent on the morphology and therefore on the choice of the processing solvent. The absorption of fiber morphologies is strongly red-shifted compared to the structureless films.
In this work, highly transparent and highly conductive thin films of Al-doped ZnO (AZO) are achieved by pulsed laser deposition (PLD). By changing substrate temperature in the range of room ...temperature to 500°C during the deposition process, the preferential growth direction of AZO crystal is controlled and, therefore, the surface morphology, optical and electrical properties of AZO thin films are able to be manipulated. X-ray diffractograms as a function of the substrate temperature clearly illustrate the ability to control the preferential growth direction of AZO. At the low substrate temperature, the growth along 002 direction corresponding to c-axis of hexagonal ZnO is only observed. By elevating the substrate temperature, not only crystallinity of AZO thin film is further improved but also the competition of crystal growth along the 002, 001 and 101 directions are occurred due to the increase of total energy and surface mobility of cluster/atom. The AZO films obtained by all preparation conditions exhibit an n-type semiconducting characteristics, furthermore, the carrier concentration and the carrier mobility of AZO thin films can be optimized to reach 4.10×1020 cm-3 and 7.53 cm2/Vs, respectively. The excellences in both carrier concentration and mobility of AZO thin film lead to very low resistivity of 2.08×10-3 Ωcm. In addition, the wide optical band gap of ∼3.50 eV together with the high transparency over 90% in visible region is obtained from the AZO thin films. The exceptional optical and electrical properties of AZO thin film demonstrate that such material has enough potential to become a promising candidate using in optoelectronic applications.
This article provides an approach to improve and control crystal phases of the sputtering vanadium oxide (VxOy) thin films by post-thermal annealing process. Usually, as-deposited VxOy thin films at ...room temperature are amorphous phase: post-thermal annealing processes (400 °C, 2 hrs) under the various nitrogen (N2) pressures are applied to improve and control the crystal phase of VxOy thin films. The crystallinity of VxOy thin films changes from amorphous to α-V2O5 phase or V9O17 polycrystalline, which depend on the pressure of N2 carrier during annealing process. Moreover, the electrical resistivity of the VxOy thin films decrease from 105 Ω cm (amorphous) to 6×10-1 Ω cm (V9O17). Base on the results, our study show a simply method to improve and control phase formation of VxOy thin films.
Polymer solar cells is one of the promising technologies that gain tremendous attentions in the field of renewable energy. Optimization of thickness for each layer is an important factor determining ...the efficiency of the solar cells. In this work, the optimum thickness of Poly(3,4-ethylenedioxythione): poly(styrenesulfonate) (PEDOT:PSS), a famous polymer widely used as hole transporting layer in polymer solar cells, is determined through the analyzing of device's photovoltaic parameters, e.g. short circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF) as well as power conversion efficiency (PCE). The solar cells were prepared with multilayer of ITO/PEDOT:PSS/PCDTBT:PC70BM/TiOx/Al by rapid convective deposition. In such preparation technique, the thickness of the thin film is controlled by the deposition speed. The faster deposition speed is used, the thicker film is obtained. Furthermore, double layer deposition of PEDOT:PSS was introduced as an approach to improve solar cell efficiency. The results obviously reveal that, with the increase of PEDOT:PSS thickness, the increments of Jsc and FF play the important role to improve PCE from 3.21% to 4.03%. Interestingly, using double layer deposition of PEDOT:PSS shows the ability to enhance the performance of the solar cells to 6.12% under simulated AM 1.5G illumination of 100 mW/cm2.
PCPDTBT, a marginally crystallizable polymer, is crystallized into a new crystal structure using solvent‐vapor annealing. Highly ordered areas with three different polymer‐chain orientations are ...identified using TEM/ED, GIWAXS, and polarized Raman spectroscopy. The optical and structural properties differ significantly from films prepared by standard device preparation protocols. Bilayer solar cells, however, show similar performance.
A set of liquid-crystalline polymeric systems, associating at once the regioregular polythiophene backbone and pending mesogenic triphenylenes, is reported. Two series, namely regular homopolymers ...and alternating copolymers, were prepared by adapting a Grignard metathesis-based methodology, allowing some of the relevant structural parameters to be sequentially and independently modified. The thermal and self-organization behaviors of these uncommon macromolecular systems were investigated by polarized-light optical microscopy, differential scanning calorimetry and temperature-dependent small-angle X-ray scattering. Most polymers self-organize into mesophases possessing intertwined lamello-columnar morphologies, resulting from the simultaneous coexistence of lamellar and columnar sublattices. The successful preparation of oriented thin films of several of these polymeric homologues allowed further investigations by atomic force microscopy, transmission electron microscopy, electron diffraction, and grazing-incidence SAXS, which provided a deeper insight of the intricate supramolecular organizational modes, including the complete elucidation of the structure of the lamello-columnar mesophases. This simple and versatile strategy provides a route to elaborate polymeric materials incorporating two intercalated separate pathways toward charge carrier transport, of paramount importance for future electronic and optoelectronic applications.
The aim of this research is to introduce the alternative process named “Rapid Convective Deposition” to obtain organic thin film in nanometer scale. There are several advantages of this method, ...including simply control film thickness via solution concentration and translational speed as well as significantly reduce required material leading to lower manufacturing cost. The specific properties of thin film were characterized by the combinations of microscopic and spectroscopic techniques. To confirm that the convective deposition has a potential to become a candidate method using to prepare thin film, the films prepared by conventional spin coating and alternative convective deposition were compared in term of processing e.g. required solution as well as processing time and film’s properties e.g. thickness, morphology and uniformity of the film. The results indicate that the rapid convective deposition is able to provide similar film’s quality as obtain from spin coating but requires less processing time and required solution to prepare the nanoscale organic thin film.
The optical transition energy in ZnSe/tris(8-hydroxyquinoline) aluminum (Alq
3)/
N,
N′-bis(3-methylphenyl)-
N,
N′-diphenyl-benzidine (TPD) heterostructure were investigated by room-temperature ...electroreflectance (ER) and photocurrent (PC) measurements. PC signal showed wavelength response of the device in the range of 450–1100
nm. ER features due to optical transition energy of the single quantum well of this structure were observed. The transition energies were determined by fitting the ER spectra to the theoretical line-shape expression. The subband transition energy decreased with increasing well thickness. Under applied voltage, both ER signals show significant shift due to the quantum confined Stark effect.
The optical transition energy in ZnSe/tris(8-hydroxyquinoline) aluminum (Alga)/N, N-bis(3-methylphenyl)-NAP-diphenyl-benzidine (TPD) heterostructure were investigated by room-temperature ...electroreflectance (ER) and photocurrent (PC) measurements. PC signal showed wavelength response of the device in the range of 450-1100 nm. ER features due to optical transition energy of the single quantum well of this structure were observed. The transition energies were determined by fitting the ER spectra to the theoretical line-shape expression. The subband transition energy decreased with increasing well thickness. Under applied voltage, both ER signals show significant shift due to the quantum confined Stark effect.
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