Special Issue “Thin-film materials, devices and carrier dynamics for flexible electronics”

Special Issue Editor

Zhigang Yin1,2 ,

* Correspondence: yinzhg@fjirsm.ac.cn

1   State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao West Road, Fuzhou, Fujian 350002, China

2   Institut für Chemie and IRIS Adlershof, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany

Interests: Optoelectronic materials and devices, Flexible electronics, Surface and interface, Charge carrier dynamics, Semiconductor physics, Solar cells, Transistors, Sensors.

Special Issue Information

Aim and Scope: Flexible electronics have attracted great attention due to their salient features and significant roles in the fields of energy, information, sensing, displays, smart skins, wearable systems, biomedical diagnostics, and artificial intelligence, etc. The past years have witnessed the rapid development of advanced materials and devices for flexible electronics. This special issue aims to collect high quality articles focused on thin-film materials, devices and carrier dynamics in flexible electronics and optoelectronics. It is desirable to search a variety of functional films including metallic, organic, inorganic, hybrid and composite materials for developing different types of flexible transistors, sensors, actuators, photodetectors, photovoltaic devices, light-emitting devices and beyond. It may contain, but not limited to material design, thin-film processing, structure regulation, property optimization, structure-property relationship, device engineering, and potential applications. Meanwhile, fundamental investigations on surface and interface characteristics, energy level alignments, charge and energy transfer processes, device operation mechanisms, and carrier dynamics related with advanced techniques such as ultrafast transient absorption and time-resolved (TR) spectroscopy, are welcome for understanding the thin-film materials and flexible devices.

We kindly invite you to submit a manuscript(s) for this Special Issue. Full papers, communications, and reviews are all welcome.

Subtopics: Synthesis and characterization of thin-film semiconductors and dielectrics; Novel electrode materials, interlayers and interface engineering; Stretchable or self-healing materials and devices; Flexible device design and electronic/optoelectronic applications; Charge transfer processes, carrier dynamics and device physics;

Keywords: films; functional materials; organic electronics; optoelectronics; flexible devices; solar cells; field-effect transistors; photodetectors; carrier dynamics; wearable applications.

Deadline for manuscript submissions: 31 December 2020

Manuscript Submission Information

All submissions to Materials International should be made at review@materials.international. The corresponding author has the responsibility of the manuscript during the submission and peer-reviewing process. Please do not forget to state in the email “Subject” the title of this special issue.

Submission Checklist

  1. read the Aim & Scope to gain an overview and assess if your manuscript is suitable for this journal;
  2. use the Microsoft Word Template to prepare your manuscript;
  3. make sure that issues about publication ethics, copyright, authorship, figure formats, data and references format have been appropriately considered;
  4. please try to cite only articles with DOI (digital object identifier); also add DOI for each reference;
  5. please add at least 10 references from the last 2 years (2018-2019) in order to highlight the novelty of your work;
  6. ensure that all authors have approved the content of the submitted manuscript.

Published papers

(1) Flexible PCB Coils for Wireless Power Transfer System Using Low-Frequency Electromagnetic Induction


Zhaofeng Zhong 1, Zan Su 1, Chuang Xu 1, Zaijun Feng 1, Zhe Wang 1, Zilin Wang 2, Yunhui Zhong 3, Hao Wu 3, Jinling Wu 4,*, Yuan-Cheng Cao 4,*

1   State Grid Yili Electric Power Supply Co. Ltd, Yili City83500, Xinjiang P.R. China

2   State grid Ezhou Electric Power Supply co., Ltd, Ezhou 43600, China

3   Zhejiang Landun Electrical New Material Technologies L.td, Hangzhou311418, China

4  School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

† these authors contributed equally to this work

*  Correspondence: yccao@hust.edu.cn; 878579346@qq.com; Scopus ID: 56979443300

Planned papers

1) Anodic polymerization of two salicyl-based monomers: Electrochemical and optical studies

Mounia Guergouri1*, Rafik Bensegueni1,2, Kharouba Madjid1, Ammar Khelifa Baghdouche1.

1Laboratoire de Chimie des Matériaux Constantine, Université des Frères Mentouri, Constantine 25000, Algeria.

2Université Mohamed Cherif Messaadia, 41000 Souk Ahras, Algérie.


We synthesized two novel monomers, 2-(9H-fluoren-7-yliminomethyl)phenol (SIF) and 2-(9-ethylcarbazol-3-yliminomethyl)phenol (SIC), by condensation between salicylaldehyde and corresponding amine, 9H-fluoren-2-amine and 9-ethyl-9H-carbazol-3-amine, respectively. Thus, we investigated the electrochemical behaviours of the two products on a GCE electrode by cyclic voltammetry. Each monomer shows two peaks, recorded vs Ag/AgCl reference electrode at 1,27 and 1,78 eV for SIF and at 1,12 and 1,45 eV for SIC. Their polymerization was achieved by a potentiostatic method in an appropriate solvent-electrolyte mixture (Bu4NBF4 (0.1 M) / MeCN). We have characterized the corresponding polymers, poly2-(9H-fluoren-7-yliminomethyl)phenol (PSIF) and poly(2-(9-ethylcarbazol-3-yliminomethyl)phenol (PSIC) by cyclic voltammetry, FT-IR and UV-vis spectroscopy. Further, we calculated the corresponding electrochemical and optical bandgaps and their values are equal to 1,43 and 1,96 eV for PSIF and 1,73 and 1,99 eV for PSIC, respectively.

Keywords: Conductive polymer, electropolymerization, cyclic voltammetry, bandgap.

2) Role of CdSe Quantum Dot on Electrical Conductivity of Chitosan/PCL Thin Films

A.M. Abdelghany1, M.S. Meikhail2 and W.M. Awad1

1 Spectroscopy Dept., Physics Division, National Research Center, 33 Elbehouth St., Cairo, 12311, Egypt.

2 Physics Department, Faculty of Science, Mansoura University, Mansoura, 35516, Egypt.


Chitosan, which has low conductivity, was blended with poly(ϵ-caprolactone), PCL, which has a fast ionic motion for facilitating ionic conduction. Besides, Semiconducting CdSe quantum dots were embedded within the thin film polymeric matrix to enable uses in different applications. The dielectric constant, ϵ’, of synthesized polymer composite, was found to be a constant with respect to temperatures and attributed to the decrease in charge carriers and their mobility. Experimental data reveal that the hopping mechanism administrates both the transport of charge carriers and also their relaxation.

            At low frequencies, the loss tangent, tan δ, increases to a maximum value with increasing frequency and then decreases again at a higher frequency. Semicircles were observed in Cole-Cole diagrams at temperature 20oC with their center below the X-axis, indicating the presence of dielectric relaxation over a wide range.

Keywords: Chitosan; PCL; thin film; CdSe; QDs; Ac Conduction.

3) On approach to increase integration rate of elements of a injection locked oscillator

E.L. Pankratov1,2

1. Nizhny Novgorod State University, 23 Gagarin avenue, Nizhny Novgorod, 603950, Russia

2. Nizhny Novgorod State Technical University, 24 Minin Street, Nizhny Novgorod, 603950, Russia


In this paper we introduce an approach to increase integration rate of elements of a injection locked oscillator. Framework the approach we consider a heterostructure with special configuration. Several specific areas of the heterostructure should be doped by diffusion or ion implantation. Annealing of dopant and/or radiation defects should be optimized. An analytical approach for modelling of technological process has been also introduced. The approach gives a possibility to analyze mass and heat transport in multilayer structures without crosslinking of solutions on interfaces between layers. The approach also gives a possibility to take into account spatial and temporal variation of parameters of considered processes. Based on this approach we analyzed manufacturing an integrated circuit to increase density of elements.

Keywords: injection locked oscillator; optimization of manufacturing; heterostructure with special configuration; analytical approach for modelling.

4) Fabrication and characterization of sol-gel screen printed Zn: CdO (ZCO) thick film for optoelectronic and photovoltaic technologies

Vipin Kumar1*, Renu Kumari1, Dhirendra Kumar Sharma1, Kapil Sharma1, V. K. Sachan2

 1 Department of Physics, KIET Group of Institutions, Delhi NCR, Ghaziabad, India

2 Department of Electronics and Communication Engg. KIET Group of Institutions, Delhi NCR, Ghaziabad, India


We present report on Zn doped (5%) CdO thick film fabricated on to the glass substrate (pre-cleaned) by using sol-gel screen –printing process. The deposited sintered Zn: CdO film were then subjected to XRD, SEM, EDX, UV-Vis spectroscopy, PL spectroscopy and dark conductivity measurement studies. The XRD study of sintered film revealed the polycrystalline nature and confirmed that Zn: CdO film belongs to cubic crystalline structure. SEM study provides the information on morphology of Zn: CdO film. The EDX study confirms the existence of Cd, O and Zn in the sintered film. The UV-Vis spectroscopy via reflectance mode confirms the direct transition of band gap with a value of 2.60 eV. PL spectra of the sintered film exhibited a strong near band edge emission located around 500 nm. The Arrhenius plot (log σDC Vs 1000/T) confirms the semiconducting nature for the sintered film.

Keywords: Sol gel screen printing, XRD, UV-Visible, PL spectra.

5) Passivating Si and Ge surfaces using a facile sonochemical method

V. Shmid, A. Podolian, А. Nadtochiy, O. Korotchenkov

Faculty of Physics, Taras Shevchenko National University of Kyiv, Kyiv 01601, Ukraine


Ultra-thin chips made from thinned Si wafers that offer remarkable levels of bendability without failure have being considered to be ideal for utilizing in flexible electronics. Of significance are also silicon-based materials, such as SiGe, which are compatible with micro-processed Si wafers and used as thin films in ultra-fast strained bipolar complementary metal oxide semiconductor (BiCMOS) channels and low-resistive contacts. Due to a lattice mismatch of Si and Ge, these Si-Ge systems provide high levels of strain thus rendering capabilities of bending and stretching on the wafer surfaces and in the interface regions. To yield heterogeneously integrated electronic devices, low surface and interface trap densities have to be achieved together with improved inter-layer coupling. Depositing a passivation film on Si and Ge surfaces, which affects the carrier recombination velocities at the surfaces, is of great interest in this respect. It was also shown that alkylated Si surfaces are less susceptible to oxidation in air than were hydrogen-terminated Si surfaces. Furthermore, extremely low recombination velocities at CH3-Si(111) surfaces ranging from 10 to 100 cm s-1 were reported. The C-H passivation patterns could also be used to define sites of a strong adhesion to the wafer surfaces. Facile sonochemical treatment steps can offer great potential for performing these tasks. To intensify a functionalization ability of Si and Ge surfaces by chemically bonded C-H chains to dangling bonds and hence improve the lifetimes in Si and Ge, here we propose sonochemical treatments in chloroform (CHCl3) and dichloromethane (CH2Cl2). It is suggested that these carbon sources are decomposed into hydrocarbon chains due to extreme conditions in the solvents and at the etchant/solid interfaces, as temperatures of »5000°C, pressures of »50 MPa and cooling rates greater than 109 K/s are achieved after the growth and following collapse of cavitation bubbles. It is implied that the carbon atoms can then form bonds with the Si and Ge surface atoms thus producing long-chain species on solid Si and Ge surfaces, which form stable surface passivation patterns. Our results show that wet chemical and sonochemical treatments in CHCl3 and CH2Cl2 improve recombination properties of Si, Ge and SiGe surfaces that have been functionalized by H-atoms in standard HF solutions prior to performing a sonochemical step. Surface photovoltage (SPV) decay curves, scanning electron microscopy (SEM) images, energy-dispersive X-ray (EDX) spectra and Fourier transformed-infrared (FTIR) transmission data are reported to show that sonochemical treatments can result in increased SPV signals and prolonged decay times. These results demonstrate that sonochemical technique is an effective tool for passivating Si, Ge and SiGe surfaces in hydrocarbon solutions.

6) New Model Predicting The electric Conductivity of Mono-, and Multilayered Highly Oriented Single-walled Carbon Nanotube Films

Maher S. Amer, Mark Foster, Ali Al Mafrage, and Mohammed K. Mohammed
Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435 USA
We developed a new model capable of accurately predicting the electrical conductivity of highly aligned single-walled carbon nanotube thin films. The films ranged between 1 and 11 layers thick. The well-established Lamination theory failed to predict the experimentally measured values for the films of different thicknesses, However, Our model, based on a modified and expanded techniques applied within realm of the lamination theory, could predict the exact values taking into consideration the inter-layer interaction that is crucial for the properties and performance of nano-films.

7) A critical review of some numerical models for thin films on elastic substrates

Daniele Baraldi

Department of Architecture, Università Iuav di Venezia, Venice, Italy



This work is dedicated to a review of a set of simple and effective numerical models for studying the behaviour of thin films on elastic substrates and/or sandwich composites. As well known, in mechanic and electronic engineering fields, thin films on elastic substrates can be modelled by means of beams on elastic supports. For this purpose, the Euler–Bernoulli beam hypothesis is here adopted for representing thin film behaviour, whereas several different laws are assumed for simulating the relationship between elastic substrate vertical displacements and contact tractions. In particular, attention is devoted to Winkler model, two parameter models, and two- and three-dimensional elastic half space models. The review is based on existing contributions, but the resulting comparison and critical evaluation of the use different models for the elastic support represents a novel contribution. In particular, the proposed approach is based on a mixed variational formulation that assumes both thin film displacements and contact tractions between the thin film and the elastic support as independent fields. Assuming perfect adhesion and no friction between the thin film and the support, the influence of the different laws for the elastic substrate is taken into account, by introducing a parameter that considers the ratio between thin film and substrate stiffness. Numerical tests focus on static and buckling analysis of thin films on elastic substrates for varying thin film length and thin film-substrate stiffness ratio.