Organic bulk heterojunction solar cells based on benzodithiophene and benzothiadiazole containing conjugated polymers

Organic photovoltaics (OPVs) or so-called organic solar cells particularly hold promise for manufacturing solar energy due to their advantages in low cost and production processes. In order to understand and improve the performance of OPVs, intense efforts have been dedicated around the world [1]. In particular, conjugated polymers are attractive for OPVs due to the π-conjugated systems in the polymer backbone which generates and transport the charge carriers [2]. Therefore, the design and synthesis of novel conjugated organic polymers play important role to obtain higher photovoltaic properties and improve the power conversion efficiencies (PCEs) of the OPVs. For this purpose, benzodithiophene and benzothiadiazole containing monomers were independently synthesized, then polymerized via Stille cross-coupling reaction to obtain P1 and P2 polymers. Oxidation and reduction behavior of the polymers were studied by cyclic voltammetry. Measurements indicated that the highest occupied molecular orbital (HOMO) levels were -5.25 eV for P1 and -5.38 eV for P2. The optical band gaps of P1 and P2 were calculated via UV-VIS-NIR spectroscopy as 1.54 eV and 1.64 eV, respectively. Bulk heterojunction solar cells were constructed with these polymers as the donor moieties together with PC71BM as the acceptor in the active layer. The current/voltage measurements showed that the highest PCEs of these photovoltaic devices were recorded as 2.52% for P1: PC71BM (1:4, w/w) in 2% DIO and 1.67% for P2: PC71BM (1:3, w/w) in 3% DIO solution

Synthesis of selenophene substituted benzodithiophene and fluorinated benzothiadiazole based conjugated polymers for organic solar cell applications

© 2021A series of alternating conjugated copolymers which contain selenophene modified benzodithiophene and fluorine bearing benzothiadiazole have been synthesized via Stille polycondensation reaction to investigate the effect of the number of fluorine atoms substituted to the benzothiadiazole. Three different polymers, PBDTSe-BT, PBDTSe-FBT and PBDTSe-FFBT, were reported and their electrochemical, spectroelectrochemical, and photovoltaic behaviors were examined. Density functional theory calculations were performed on model tetramer structures to shed light on how substituting the fluorine atom to the acceptor building block affects the structural, electronic and optical properties of the polymers. The results of computational studies were compared with experimental studies. The structure adjustment accomplished by fluorine substitution on the benzothiadiazole moiety reveals an influence on the electronic structure of polymers with a more negative HOMO energy level. A high VOC for the resulting photovoltaic device was examined for PBDTSe-FFBT. Difluorinated polymer PBDTSe-FFBT:PC71BM organic solar cell exhibited the highest photovoltaic performance of 2.63% with JSC of 7.24 mA cm-2, VOC of 0.72 V and FF of 50.6%. PBDTSe-BT:PC71BM revealed the best PCE as 2.39%, and the device reached the highest efficiency up to 1.68% for PBDTSe-FBT:PC71BM

Döner rotorlu ̇İHA kontrol sistem tasarımı ve uygulaması.

In this thesis, a hybrid vertical take off and landing unmanned air vehicle platform is designed and developed. The platform uses tricopter configuration for takeoff and landing while it uses its fixed wings for forward flight. Control algorithms are developed for the VTOL aircraft. For this purpose, first nonlinear simulation code is developed in Matlab/Simulink environment. The simulation uses the wind tunnel experimental data for the propellers and aerodynamic data obtained from a package program XFLR 5 that uses panel method. The controller uses Linear Quadratic Tracking (LQT) algorithms for vertical takeoff, transition and forward flight cases. For different flight phases, trim flight conditions are obtained and controllers are designed. During transition, weighted pseudo inverse and blended inverse control allocation methods are employed and simulation results are compared. The obtained controller gains are tuned in the lab test setup and flight tests are performed for vertical takeoff and landing flight, demonstrating acceptable flight performance.Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering

Piezoelektrik katmanlı plakaların tabakasal yaklaşımla modellenmesi

In this thesis, optimal placement of adhesively bonded piezoelectric patches on laminated plates and the determination of geometry of the bonding area to maximize actuation effect are studied. A new finite element model, in which each layer is considered to be a separate plate, is developed. The adhesive layer is modeled as a distributed spring system. In this way, relative transverse normal and shear motion of the layers are allowed. Effect of delamination on the adhesive layer stresses is also studied and investigated through several case studies. Optimization problems, having single and multiple objectives, are investigated for both actuator placement and selective bonding examples. In these case studies, 2D and 3D Pareto fronts are also obtained. ءHide and Seek Simulated Annealing̕ method is adapted for discrete problems and used as the optimization technique for single-objective problems. Finally, Multiple Cooling Multi Objective Simulated Annealing optimization algorithm is adapted and used in multi-objective optimization case studies.Ph.D. - Doctoral Progra

Neural Network Modeling of AChE Inhibition by New Carbazole-Bearing Oxazolones

Acetylcholine esterase (AChE) is one of the targeted enzymes in the therapy of important neurodegenerative diseases such as Alzheimer's disease. Many studies on carbazole- and oxazolone-based compounds have been conducted in the last decade due to the importance of these compounds. New carbazole-bearing oxazolones were synthesized from several carbazole aldehydes and p-nitrobenzoyl glycine as AChE inhibitors by the Erlenmeyer reaction in the present study. The inhibitory effects of three carbazole-bearing oxazolone derivatives on AChE were studied in vitro and the experimental results were modeled using artificial neural network (ANN). The developed ANN provided sufficient correlation between several dependent systems, including enzyme inhibition. The inhibition data for AChE were modeled by a two-layered ANN architecture. High correlation coefficients were observed between the experimental and predicted ANN results. Synthesized carbazole-bearing oxazolone derivatives inhibited AChE under in vitro conditions, and further research involving in vivo studies is recommended. An ANN may be a useful alternative modeling approach for enzyme inhibition

Electrosynthesis and characterization of an electrochromic material containing biscarbazole-oxadiazole units and its application in an electrochromic device

Electroactive poly(2,5-Bis(9-methyl-9 H-carbazol-3-yl)-1,3,4-oxadiazole) (PolyBCO) film was synthesized to form a highly stable conducting polymer with excellent electrochromic properties. The polymer was characterized by cyclic voltammetry, UV-Vis-NIR spectroscopy and colorimetry. Spectroelectrochemistry analysis demonstrated that the polymer can undergo both p-type and n-type doping processes. The polymer has four accessible color states. Further kinetic studies demonstrated that the polymer revealed high contrast ratio (75%), fast response time (0.9 s), excellent stability and color persistence. A dual-polymer electrochromic device was constructed in sandwich configuration where PolyBCO was used as the anodically coloring material. The device switches between a transmissive light gray state and a blue-colored state with a fast response time and high stability

Synthesis of new ibuprofen derivatives with their in silico and in vitro cyclooxygenase-2 inhibitions

Cyclooxygenase-2 (COX-2) is one of the important targets for treatment of inflammation related diseases. In the literature, most of drug candidates are first synthesized and then their COX-2 inhibitory activities are tested by in vitro and in vivo experiments. However, synthesis of dozens of drug analogues without any interpretations on their inhibitory activity can result in loss of time and chemicals. Therefore, synthetic drug designs with molecular modeling are of importance to synthesize selective drug candidates against inflammatory diseases. The synthesis of the novel ibuprofen derivatives through their in silico and in vitro COX-2 inhibitory activities were investigated in the present study. Starting from ibuprofen, ibuprofen amide and ibuprofen acyl hydrazone derivatives were synthesized. According to the results of the in silico molecular docking and in vitro enzyme inhibition studies, the synthesized novel ibuprofen derivatives have selective COX-2 inhibition, and molecule 3a and 3c were showed higher inhibition compared to ibuprofen. In conclusion, the newly synthesized ibuprofen derivatives can be used in model in vivo studies. (C) 2013 Elsevier Inc. All rights reserved

Alkyl-end phenanthroimidazole modification of benzotriazole based conjugated polymers for optoelectronic applications

A new triazoloquinoxaline and benzodithiophene based copolymer was synthesized to investigate its electrochemical, optical and photovoltaic behaviors. According to the polymer design, combination of two acceptor units (benzotriazole and quinoxaline) which contribute imine bonds to the structure and a triazoloquinoxaline unit for enhancing electron accepting ability was pursued. As a result of electrochemical studies, the copolymer PTQBDT has a low lying HOMO energy level as −5.23 eV which increases the chemical stability of the resulting polymer and leads to a higher Voc. In addition, the copolymer has an ambipolar character with two well-defined redox couples in the n-doped state and multichromic behavior. In the context of optical studies, PTQBDT has wide absorption range in the visible region with a tail in the NIR region, which yields a low band gap of 1.20 eV. Organic photovoltaic devices were designed using PTQBDT (the electron donor) and PC71BM (the electron acceptor) for the preliminary studies. The resulting device exhibits a power conversion efficiency of 2.0% with a current density of 8.07 mA cm−2 , an open-circuit voltage of 0.45 V, and a fill factor of 55%. The carrier mobility of the PTQBDT was calculated as 3.00 × 10−3 cm2 V−1 s −1 via space-charge-limited current (SCLC) method