■Electrical and Electronic Engineering

4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) was synthesized in order to facilitate the hole-injection in Organic Light Emitting Diodes (OLED). MPPBA was applied to form self-assembled monolayer (SAM) on indium tin oxide (ITO) anode to align energy-level at the interface between organic semiconductor material (TPD) and inorganic anode (ITO) in OLED devices. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). KPFM was used to measure the surface potential and work function between the tip and the ITO surface modified by SAM technique using MPPBA. The OLED devices (ITO/MPPBA/TPD/Alq3/Al) fabricated with SAM-modified ITO substrates showed lower turn-on voltages and enhanced diode current compare to the OLED devices fabricated with bare ITO substrates.► Two different OLED structures with SAM and without SAM were fabricated. ► The SAM layer enhances the luminous and quantum efficiency. ► The SAM layer improves the turn-on voltage and diode current of OLED devices.

In order to understand the electronic prop ert ies of the organic S chottky dio d e, ITO/TPD/Al and IT O/SAM /
TPD/Al organic Schottky devices were fabricated t o obtain currentvoltage characteristics. From the slop es and
y -axis intercepts of the plots, the values of the ideality factor, barrier heights of the ITO/SAM/TPD/Al dio de
were determined as 2.03 and 0.56 eV, resp ectively. The surface characterizat ions of mo died and unmo died ITO
were p erformed via at omi c force microscopy.

Humidity adsor ption kinetics of chitosan films was investigated by quar tz cr ystal microbalance
(QCM) technique. In this study, chitosan was synthesized from chitin by deacetylation process in
2.0% (v/v) acetic acid solution and then coated on QCM to measure humidity response. The Lang-muir model was used to deter mine the adsor ption rates and Gibbs free energy for var ious relative
humidity between 11% and 94%. The average Gibbs free energy for adsor ption was obtained as
−12  93 kJ/mol. Our reproducible exper imental results show that chitosan films are ver y sensitive to
relative humidity changes at room temperature

4-[(3-Methylphenyl)(phenyl)amino]benzoic acid (MPPBA) self-assembled monolayer (SAM) molecules as hole injection is formed on p and n type Si and on indium-tin oxide (ITO) electrodes to investigate the effect on the electrical parameters of hole only organic device. The hole mobility improvement of organic device was attributed to an intermediate energy level formed between hole transport materials (HTL) (N,N-Bis(naphthalen-1-yl)-N,N-bis(phenyl)benzidine-NPB) and ITO when forming an ultrathin MPPBA layer, leading to increase of carrier mobility of the device. Space charge limited current (SCLC) technique is used to estimate the mobility of the NPB formed at the interface metal/organic Ohmic contact. The hole mobility of ITO/NPB/Al and ITO/MPPBA/NPB/Al devices were obtained as 1.80 × 10 −6 and 1.76 × 10 −3 cm 2 /Vs, at 1350 E (V/cm) 1/2 applied electric field, respectively. SAM modified devices has lower barrier height values. The electronic characteristic parameters of the ITO/(with or without MPPBA)/NPB/Al, Au/n-Si(or p-Si)/(with or without MPPBA)/Au contacts were calculated using current–voltage (I–V) measurements by Schottky type carrier injection.

In this study, the ruthenium complexes, which is an organometallic N-3 and C-106 semiconductor
material, was coated on indium tin oxide (ITO) by using the self-assembled technique and thus a
diode containing an organometallic interface was produced. The effects of this interface on the electronic parameters of the diode were investigated. It is aimed to improve the heterogeneity problem
of the inorganic/organic interface by chemically bonding these materials from COOH active parts to
the ITO surface. In order to understand how the electronic parameters of the diode change with this
modification, the Schottky diode electrical characterization approach has been used. The charge
mobility of the diode was calculated using the current density-voltage curve (J–V ) characteristic
with Space Charge Limited Current (SCLC) technique. When the electrical field is applied to the
diode, it can be said that the ruthenium complexes molecules create an electrical dipole and the
tunneling current is transferred to the anode contact ITO through the ruthenium molecule through
the charge carrier, thus contributing to the hole injection. The morphology of these interface modifications was examined by Atomic Force Microscope (AFM) and surface potential energy by Kelvin
Probe Force Microscope (KPFM). To investigate local conductivity of bare ITO and modified ITO
surface, Scanning Spreading Resistance Microscopy (SSRM) that is a conductive AFM analyzing
technique were performed by applying voltage to the conductive tip and to the sample. According
to the results of this work the diode containing N-3 material shows the best performance in terms
of charge injection to the ITO due to possess the lowest barrier height êb as 0.43 eV.

This work focused on synthesizing of the electro active two small molecules ((2E)-2-Cyano-3-[4'-(2,5-di-2 thienyl-1H-pyrrol-1-yl) biphenyl-4-yl] acrylic acid (MC-20) (2E)-2-Cyano-3-5-[4-(2,5-di-2-thienyl-1H pyrrol-1 yl) phenyl]-2-thienyl acrylic acid (MC-28)) consisting of planar molecule part with different absorptions-emissions energy levels and applications of these small molecules in DSSC device to understand their performance. The optical properties of MC-20 and MC-28 were determined by UV-Vis absorption and fluorescence measurements, and electrochemical properties were illuminated by cyclic voltammetry (CV). The 1 H-NMR spectroscopy is used to characterize the molecular structure of the synthesized materials. The obtained electrochemical and optical data were used to calculate Highest Occupied Molecular Orbital-Lowest Unoccupied Molecular Orbital (HOMO-LUMO) band gaps. As a result, these synthesized molecules have been used in Dye sensitized solar cells (DSSCs). The performance of these materials was analyzed by calculating the efficiency of the DSSC device. Obviously, it can be said that linking different donor atom S to the molecule has a little positive effect on photovoltaic efficiency.

A carboxylic group functioned charge transporting was synthesized and self-assembled on an indium tin oxide (ITO) anode. A typical electroluminescent device [modified ITO/TPD (50 nm)/Alq 3 (60 nm)/LiF (2 nm)/(120 nm)] was fabricated to investigate the effect of the amino groups-small molecules interface on the characteristics of the device. The increase in the surface work function of ITO is expected to facilitate the hole injection from the ITO anode to the Hole Transport Layer (HTL) in electroluminescence. The modified electroluminescent device could endure a higher current and showed a much higher luminance than the nonmodified one. For the produced electroluminescent devices, the I-V characteristics , optical characterization and quantum yields were performed. The external quantum efficiency of the modified electroluminescent device is improved as the result of the presence of the amino groups-small molecules interface.

Abstract The effects of surface modification of titanium dioxide (TiO 2 ) on the performance of inverted type organic solar cells ( i- OSCs) was investigated in this study. A series of benzoic acid derivatized self-assembled monolayer (SAM) molecules of 4′-[(hexyloxy)phenyl]amino-3,5-biphenyl dicarboxylic acid (CT17) and 4′-[1-naphthyl (phenyl)amino]biphenyl-4-carboxylic acid (CT19) were utilized to modify the interface between TiO 2 buffer layer and poly-3 hexylthiophene (P3HT):[6,6]-phenyl C 61 butyric acid methyl ester (PC 61 BM) active layer having the device structure of ITO/TiO 2 /SAM/P3HT:PC 61 BM/MoO 3 /Ag. The work function and surface wetting properties of TiO 2 buffer layer served as electron transporting layer between ITO and PC 61 BM active layer were tuned by SAM method. The solar cell of the SAM modified devices exhibited better performance. The power conversion efficiency (PCE) of i- OSCs devices with bare TiO 2 electrodes enhanced from 2.00% to 2.21% and 2.43% with CT17 and CT19 treated TiO 2 electrodes, respectively. The open circuit voltage (V oc ) of the SAM treated TiO 2 devices reached to 0.60 V and 0.61 V, respectively, while the V oc of untreated TiO 2 was 0.57 V. The water contact angle of i- OSCs with CT17 and CT19 SAMs was also higher than the value of the unmodified TiO 2 electrode. These results show that inserting a monolayer at the interface between organic and inorganic layers is an useful alternative method to improve the performance of i- OSCs.

Abstract Organic semiconductor (OSC) materials as a charge carrier interface play an important role to improve the device performance of organic electroluminescent cells. In this study, 4,4″-bis(diphenyl amino)-1,1':3′,1″-terphenyl-5'-carboxylic acid (TPA) and 4,4″-di-9H-carbazol-9-yl-1,1':3′,1″-terphenyl-5'-carboxylic acid (CAR) has been designed and synthesized to modify indium tin oxide (ITO) layer as interface. Bare ITO and PEDOT:PSS coated on ITO was used as reference anode electrodes for comparison. Furthermore, PEDOT:PSS coated over CAR/ITO and TPA/ITO to observe stability of OSC molecules and to completely cover the ITO surface. Electrical, optical and surface characterizations were performed for each device. Almost all modified devices showed around 36% decrease at the turn on voltage with respect to bare ITO. The current density of bare ITO, ITO/CAR and ITO/TPA were measured as 288, 1525 and 1869 A/m2, respectively. By increasing current density, luminance of modified devices showed much better performance with respect to unmodified devices.

Hole tasima malzemesi olarak islev goren bir organik bilesik (1'-4-iyodofenil) trihidroksisilan (OH-IPhSi) sentezlendi ve indiyum kalay oksit (ITO) anodu uzerinde kendinden organize tek tabaka (KOT) olarak kaplandi. Bir KOT katmaninin, bir organik isik yayan diyot (Organik LED) uzerindeki etkisini arastirmak icin, tipik bir Organik LED cihazi (ITO / OH-IPhSi / polimer / LiF / Al) yapilmistir. KOT ile modifiye edilmis cihaz, ciplak ITO cihazindan daha yuksek bir mobilite gostermistir. Bunun yani sira, yuklerin mobilite ozelliklerinin, polifloren (PFO) polimer Organik LED cihazlari icin space charge limitli akim (SCLC) teknigi kullanilarak hesaplanmistir.

This work focuses on characterization the performance of enhanced interface of organic light emitting diode (OLED) device by Self-assembled Monolayer (SAM) technique. SAM technique is popular in order to overcome the weak bonding at the organic/inorganic interface in OLED. New generation of SAM molecules, phenyl-benzoic-acid (PBA, 4-(9H-carbazol-9-il) benzoic acid (MZ39), 4-(2,5-di-2thienyl-1H-pyrrol-1-il) benzoic acid (MZ25) were coated on between Indium Tin Oxide (ITO). The two configuration of ITO/SAM/TPD/Al and ITO/TPD/Al diode were fabricated as hole-only device to show the contribution of SAM layer on the hole mobility calculated by Space Charge Limited Current (SCLC) technique. The optical characterization of OLED devices with configuration ITO/TPD/Alq3/Al and ITO/SAM/TPD/Alq3/Al was performed to see the effect of aromatic SAM molecules on the luminance and quantum efficiency. Especially, the SAM modified OLED has a maximum luminance of 397 cd m−2. All devices containing SAM ...

Abstract. Cadmium selenide (n-CdSe) thin films were grown on a silicon substrate with a polished surface and applied to the Schottky type device structure. The n-CdSe thin films produced depended on various deposition times at 70°C by the use of the chemical bath deposition technique. XRD results show that the fabricated thin films consist of both cubic and hexagonal crystal systems. The morphology of CdSe was formed in nanograins and nanowire structures with respect to deposition times of 6 and 10 h, respectively. In addition to structural analysis of CdSe thin films, CdSe nanowires were used as an interfacial layer in a metal–semiconductor device to investigate its effects on the electrical and photosensitive characteristics of the device. As well as under forward bias current–voltage (I  −  V) conditions, the space charge limited current conduction behaviors were identified at low voltages. The results showed that the film produced at 10 h has a better performance compared to that produced at 6 h in terms of increased electric current.

This study focuses on characterization and enhancement of indium tin oxide (ITO) surface by using a self-assembled monolayer (SAM) technique. It is generally used to establish a compatible interface and a good charge injection from ITO surface. New generation organic semiconductor molecules such as dibenzo[ a , c ]phenazine-11-carboxylic acid, 4-(9 H -carbazol-9-yl) benzoic acid, 4-(2,5-di-2-thienyl-1 H -pyrrol-1-yl) benzoic acid, 5-[(diphenyl) amino]isophthalic acid and 5-[(3-methylphenyl)(phenyl)amino]isophthalic acid were coated on ITO. The surface of ITO was characterized by scanning spreading resistance microscopy, Kelvin probe force microscopy, scanning tunnelling microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry techniques to ensure the chemical bonding of SAM materials on it.