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8. Utilizing a Carbazole‐Incorporated Regioisomeric Synthesis Strategy to Design Hole Transporting Materials for Perovskite Solar Cells.

Author

Yeşil, Tamer, Mutlu, Adem, Başak Turgut, Sevdiye, Gültekin, Burak, and Zafer, Ceylan

Subjects
*FRONTIER orbitals, *BAND gaps, *ENERGY levels (Quantum mechanics), *SOLAR cell efficiency, *ELECTRON delocalization, *CARBAZOLE
Abstract

Two new p‐type molecules, namely TAT‐TY3 and TAT‐TY4, featuring triazatruxene endcaps and carbazole π‐bridges, were synthesized. The photophysical and electrochemical properties of synthesized materials were comparatively investigated based on their 2,7‐ and 3,6‐carbazole conjugation pathways. Optical characterizations revealed the impact of non‐bonding electron delocalization of triazatruxene through carbazole moieties, resulting in a significant increase in absorption intensity corresponding to n‐π* energy transitions and a red shift of triazatruxene moieties. Consequently, the optical band gaps of TAT‐TY3 and TAT‐TY4 were measured at 3.0 and 3.2 eV, respectively. Moreover, the molecules′ first oxidation potentials exhibited a drastic difference due to the electrochemical behavior of 2,7‐ and 3,6‐carbazole moieties. The highest occupied molecular orbital (HOMO) level for TAT‐TY3 was measured to be −5.02 eV, while for TAT‐TY4, it was measured as −4.67 eV. Hole‐extraction properties were explored using steady‐state and time‐resolved photoluminescence spectroscopy, revealing enhanced charge transfer between the TAT‐TY3/Perovskite interface due to the better alignment of HOMO energy levels. The photovoltaic performances of the hole‐transporting materials (HTMs) were successfully characterized in triple‐cation perovskite solar cells and efficiencies of up to 17.9 %, 16.2 %, and 9.8 % were achieved for Spiro‐OMeTAD, TAT‐TY3, and TAT‐TY4, respectively. [ABSTRACT FROM AUTHOR]

Published
2024
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11. Electrical characterization of Ag/MoO3−x/p-Si Schottky diodes based on MoO3−x synthesized via sol–gel method: an investigation on frequency and voltage dependence.

Author

Mutlu, Adem and Tozlu, Cem

Abstract

MoO3−x is a commonly used buffer layer in organic based optoelectronic devices to align energy level between active semiconductor and metal layer. The purpose of this study is to show the effects of the MoO3−x interlayer by comparing with a reference device without MoO3−x interlayer. To evaluate the effect of MoO3−x interlayer synthesized by sol–gel method, basic important parameters such as ideality factor (n), barrier height (∅ B), interface states (Nss) and series resistance (Rs) of Ag/MoO3−x/p-Si and Ag/p-Si Schottky diodes were calculated by electrical characterization methods. The current–voltage (I–V) measurements show that the ideality factor for the p-Si/Ag reference diode was decreased from 2.4 to 1.9 while rectification factor increasing 44.6 times using MoO3−x interlayer, and frequency–dependent measurements (C–V–f, G–V–f) were carried out to elucidate this deviation at room temperature for MoO3−x-based diode. From the XPS analysis, it was seen that Mo+6 and Mo+5 oxidation states were intense on the surface of the MoO3−x film, and the Mo+4 oxidation state increased as it went into the bulk. The changes in Rs and Nss due to the energy levels formed by the Mo+6 and Mo+5 oxidation steps at the interface are depicted. In addition, the energy density distribution profile of Nss was obtained using the I–V characteristics for various forward bias voltages range from 2.1 × 1012 to 2.5 × 1012 eV−1 cm−2. Based on the experimental results, the sol–gel synthesized MoO3−x thin film exhibits favorable rectification characteristics and holds promise for application as a Schottky diode. [ABSTRACT FROM AUTHOR]

Published
2024
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18. Investigation of the degradation mechanisms in perovskite solar cells and stability improvement

Author

Mutlu, Adem, Zafer, Ceylan, and Ege Üniversitesi, Fen Bilimleri Enstitüsü, Güneş Enerjisi Ana Bilim Dalı

Subjects
Silver Bismuth Iodide, Verim, Triple-Cation Perovskite, Anti-Çözücü, Efficiency, Kararlılık, Solar Cell, Methyl Ammonium Bismuth Iodide, Güneş Hücresi, Kurşunsuz Perovskite, Metil Amonyum Bizmut İyodür, Anti-Solvent, Gümüş Bizmut İyodür, Lead-Free Perovskite, Stability, Üçlü Katyon Perovskite
Abstract

Fotovoltaik araştırmalarındaki en yeni başarı örneklerinden biri, güneşten elektriğe yüksek güç dönüşüm verimliliği (PCE) sunan organometal kurşun halojenür perovskite güneş hücrelerinin ortaya çıkmasıdır. Bununla birlikte, toksik kurşunun varlığı ve kararsızlığı, toksik olmayan, çevre dostu, doğada daha çok bulunan, daha basit ve yapısal olarak daha kararlı, yüksek performansla çalışabilecek yeni ışık soğuran malzemelerin arayışına yol açmıştır. Bu tezin ilk bölümünde, benzil klorür (BCl) ve benzil bromür (BBr) gibi iki farklı reaktif, tek aşamalı kaplama yöntemi ile oluşturulan üçlü katyon perovskite ince filmlerde Kornblum oksidasyon reaksiyonları kullanılarak yapısal deformasyonları ve kararlılık problemlerini ortadan kaldırmak için anti-çözücü olarak uygulanmıştır. BBr anti-çözücüsü ile yıkanarak üretilen perovskite güneş hücresinde (PSC) yük rekombinasyonunu azalttığı ve referans klorobenzen (CB) ile yıkamaya kıyasla 1100 mV' luk daha yüksek bir açık devre gerilimi (VOC), iyileştirilmiş yük aktarımı ile %19,2 güç dönüştürme verimliliği (PCE) sağlayarak en iyi aygıt performansı elde edilmiştir. BBr ile yıkanan ince filmlerde artık kalan DMSO ve Pb-DMSO komplekslerinin tamamen uzaklaştırılmasıyla, aygıt performanslarında 1 ay sonra ilk günkü verimliliğin %94' ünü koruyan daha kararlı ve yüksek verimli güneş hücreleri elde edilmiştir. İkinci bölümde, yüksek kristalliğe sahip, yüzey kusurları içermeyen, pürüzsüz metilamonyum bizmut iyodür (MBI) aktif katmanı elde etmek için çeşitli yeşil çözücü sistemleri kullanılmıştır. Tetrahidrofuran: 2-etoksietanol (THF:2ETO) çözücü sistemi ile hazırlanan MBI yapısının en yüksek film kalitesine sahip olduğu bulunmuştur. Yardımcı çözücü olarak 0,05 M 2ETO eklemek, yüksek kaliteli BiI3 ve MBI ince filmler üretmek için yeterlidir. X-ışını fotoelektron spektroskopisi (XPS) analizlerine göre, ana çözgen olan THF' ye eklenen 2ETO konsantrasyonuna göre BiI3 ve 2ETO arasında bir etkileşim olduğu gösterilmiştir. Bu çalışma ile, yüksek kaliteli BiI3 veya MBI ince filmler oluşturarak bizmut tabanlı güneş hücrelerinin evrimini hızlandırabilecek olan THF-2ETO çözücü sisteminin önemi ortaya koyulmuştur. Üçüncü bölümde, Ag3BiI6 güneş hücrelerinde karşılaşılan metalik Bi0 türlerini bastırmak için bakır (I) bromür (CuBr) eklenerek cihaz verimi ve kararlılığı arttırılmıştır. XPS ölçümleri, az miktarda CuBr eklenmesinin, üretim sürecinde karşılaşılan, kararlılığı ve verimi olumsuz etkileyen az miktarda metalik Bi0 oluşumunu baskıladığını göstermiştir. En yüksek verimliliğe sahip CuBr-AgI-BiI3 sistemi ile üretilen cihazlar, kontrol cihazının performansını %0,4'ten %0,7'ye yükseltmiştir ve dayanıklılığı önemli ölçüde arttırılmıştır. 7 haftalık kararlılık testi sırasında, kontrol cihazının başlangıç verimliliğinde %40'lık bir düşüş gözlemlenirken, az miktarlarda CuBr eklendiğinde ise verimlilikte %11,4'lük bir düşüş gözlemlenmiştir. Bu çalışma, Ag3BiI6 güneş hücrelerinin üretim sürecinde ortaya çıkan metalik Bi0 türlerini bastırmak ve cihaz verimliliğini ve kararlılığını artırmak için bakır (Cu) katkısını içeren oldukça etkili bir yaklaşım sunmaktadır., One of the most recent examples of success in photovoltaic research is the emergence of organometal lead halide perovskite solar cells that offer high power conversion efficiency (PCE) from solar to electricity. However, the presence and instability of toxic lead has led to the search for new light-absorbing materials that are non-toxic, environmentally friendly, more abundant in nature, simpler and more structurally stable, and capable of operating with high performance. In the first chapter of this thesis, two different reagents such as benzyl chloride (BCl) and benzyl bromide (BBr) are applied as anti-solvents to eliminate the structural deformations and stability problems utilizing the Kornblum oxidation reactions in the triple-cation perovskite thin films formed by the one-step coating method. In the perovskite solar cell fabricated by washing with BBr antisolvent, it reduces the charge recombination in perovskite solar cell (PSC) and provides a higher open circuit voltage (VOC) of 1100 mV compared to washing with reference chlorobenzene (CB), yielding a 19.2% power conversion efficiency (PCE) with improved charge transport. Removal of the residual DMSO and Pb-DMSO complexes via washing with BBr results in achieving more stable and highly efficient solar cells, which maintained 94% of the initial efficiency after 1 month. In chapter 2, various green solvent systems have been used to obtain a smooth methylammonium bismuth iodide (MBI) active layer with high crystallinity, pin-hole free. The MBI structure prepared with tetrahydrofuran:2-ethoxyethanol (THF-2ETO) solvent system was found to have the best film quality. Adding 0.05M 2ETO as the co-solvent is sufficient to produce high quality BiI3 and MBI thin films. According to the X-ray photoelectron spectroscopy (XPS) analyzes, we have demonstrated that there is an interaction between BiI3 and 2ETO according to the concentration of 2ETO added to the main THF. Our study clarifies the importance of THF-2ETO solvent system that can accelerate the evolution of the bismuth based solar cells by creating high-quality BiI3 or MBI thin films. In chapter 3 of this thesis, to suppress metallic Bi0 species encountered in Ag3BiI6 solar cells, copper (I) bromide (CuBr) was added to increase device efficiency and stability. XPS measurements have shown that the addition of a small amount of CuBr suppresses the formation of a small amount of metallic Bi0 from the manufacturing process. The devices produced with the highest efficiency CuBr-AgI-BiI3 system increased the performance of the control device from 0.4% to 0.7% and substantially improved durability. During the 7-week stability test, we observed an 40% decrease in the initial efficiency of the control device, while we noticed an 11.4% decrease in the efficiency when adding small amounts of CuBr. This study offers a highly effective approach that involves Cu doping to suppress metallic Bi0 species that appear in the production process of Ag3BiI6 solar cells and increase device efficiency and stability.

Published
2021

21. Impact of Li passivation on recombination and charge transfer at the TiO2/perovskite interface.

Author

Erdinç, Ali Koray, Mutlu, Adem, Gültekin, Burak, and Zafer, Ceylan

Abstract

This research aims to comprehensively examine the dynamics of charge transfer occurring at the interface of Li-doped titanium dioxide (TiO2) and perovskite. The specific focus is on investigating the mitigation of intrinsic defects at the interface between the electron transport layer (ETL) and perovskite, aiming to understand and address trap-assisted recombination. Compared to the pristine control cell, the Li-doped TiO2-based perovskite solar cell (PSC) showed a notable improvement in conversion efficiency, increasing from 17.6 to 20.2%. Additionally, the open circuit voltage (Voc) value increased from 1090 to 1120 mV, accompanied by a decrease in current density–voltage (J–V) hysteresis upon doping. The introduction of Li-doping led to a notable enhancement in recombination resistance, signifying a reduced recombination rate and improved charge transfer at the interface. These observations were evident in electrochemical impedance spectroscopy (EIS) measurements conducted both in the absence and in the presence of light. Furthermore, various charge transfer kinetics, such as charge transfer resistance, recombination lifetime, and diffusion length, were calculated to fully clarify the effect of Li passivation. EIS analysis demonstrated that the TiO2:Li-based solar cell displayed increased recombination resistance, suggesting enhanced charge carrier dynamics at the TiO2/perovskite interface compared to the bare TiO2. Additionally, the reduction in trap-assisted recombination, as indicated by improved chemical capacitance, recombination lifetime, and diffusion length values upon Li passivation, underscores the effectiveness of this approach in optimizing solar cell performance. The research delved into the impact of Li passivation on the TiO2/perovskite interface and the performance of PSCs by examining structural, optical, morphological, and electronic aspects.Graphical abstract: This research aims to comprehensively examine the dynamics of charge transfer occurring at the interface of Li-doped titanium dioxide (TiO2) and perovskite. The specific focus is on investigating the mitigation of intrinsic defects at the interface between the electron transport layer (ETL) and perovskite, aiming to understand and address trap-assisted recombination. Compared to the pristine control cell, the Li-doped TiO2-based perovskite solar cell (PSC) showed a notable improvement in conversion efficiency, increasing from 17.6 to 20.2%. Additionally, the open circuit voltage (Voc) value increased from 1090 to 1120 mV, accompanied by a decrease in current density–voltage (J–V) hysteresis upon doping. The introduction of Li-doping led to a notable enhancement in recombination resistance, signifying a reduced recombination rate and improved charge transfer at the interface. These observations were evident in electrochemical impedance spectroscopy (EIS) measurements conducted both in the absence and in the presence of light. Furthermore, various charge transfer kinetics, such as charge transfer resistance, recombination lifetime, and diffusion length, were calculated to fully clarify the effect of Li passivation. EIS analysis demonstrated that the TiO2:Li-based solar cell displayed increased recombination resistance, suggesting enhanced charge carrier dynamics at the TiO2/perovskite interface compared to the bare TiO2. Additionally, the reduction in trap-assisted recombination, as indicated by improved chemical capacitance, recombination lifetime, and diffusion length values upon Li passivation, underscores the effectiveness of this approach in optimizing solar cell performance. The research delved into the impact of Li passivation on the TiO2/perovskite interface and the performance of PSCs by examining structural, optical, morphological, and electronic aspects. [ABSTRACT FROM AUTHOR]

Published
2024
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22. The effect of organic/metal oxide hybrid buffer layers on the organic solar cell efficiency

Author

Mutlu, Adem, Mutlu, Adem, Tozlu, Cem, and İleri Teknolojiler Anabilim Dalı

Subjects
Energy, SAM, Anot ve katot tampon tabaka, Organik güneş hücresi, Enerji
Abstract

Bu tezde, metal oksit anot ve katot elektrot tampon tabaka üzerinde kendiliğinden organize olan moleküllerin (SAM) dizilimi ile üretilen geleneksel ve devrik yapıdaki organik güneş hücrelerinin verimliliği üzerine etkileri incelenmiştir. Anot ve katot tampon tabakada etkin yük transferini gerçekleştirmek amacıyla, birbirinden farklı merkezde tiyofen molekülü içeren akseptör özellikli dört adet SAM malzemesi MoO3 ve ITO yüzeyleriyle, amin gruplarını içeren birbirinden farklı üç adet SAM molekülleriyle TiO2 metal oksit yüzeyi arasında monodante bağ yapısı oluşturulmuştur. Geleneksel olarak üretilen organik güneş hücrelerinin sonuçlarına göre ITO/SAM/MoO3 hibrit elektrot yapısının anot tampon tabaka yük transferi için uygun enerji band profiline sahip olduğu anlaşılmıştır. Standart olarak hazırlanan ITO/MoO3/P3HT:PCBM/Ca/Ag güneş hücre yapısından elde edilen %1,93 verimlilik değeri, SAM moleküllerinin kullanıldığı ITO/SAM/MoO3/P3HT:PCBM/Ca/Ag hücre yapısıyla daha yüksek verimlilik değerlerine çıkarılmıştır. En yüksek verimlilik değeri tek florlu ZE-1F SAM molekülünden %2,22 olarak elde edilmiştir. ITO/TiO2/P3HT:PCBM/MoO3/Ag devrik yapıda üretilen standart güneş hücresinden elde edilen %2,0' lik verimlilik değeri, SAM moleküllerinin kullanıldığı ITO/TiO2/SAM/P3HT:PCBM/MoO3/Ag yapısıyla arttırılmıştır. En yüksek verimlilik değeri MK120 molekülünden %2,43 olarak elde edilmiştir. In this thesis, the hybrid anode and cathode buffer layer which consists of self-assembled monolayers on the metal oxide anode and cathode electrode effects was investigated on the efficiency conventional and inverted type organic solar cells. In order to achieve the effectively charge transfer through anode and cathode buffer layer, the four different self-assembled monolayers consisting of acceptor moiety in the center of thiophene molecules centers structure forming a monodanthe bond structure between MoO3 and ITO surfaces and the three different self-assembled monolayers containing of amine groups forming a monodanthe bond structure between TiO2 surfaces. According to the results, the energy bands profile of ITO/SAM hybrid electrode structure understood to have the appropriate profile for charge carrier transfer in conventional type solar cells. The average 1,93% efficiency is obtained from the structures ITO/MoO3/P3HT:PCBM/Ca/Ag that use SAM molecules ITO/SAM/MoO3/P3HT:PCBM/Ca/Ag structure were obtained higher efficiencies. The highest efficiency value was obtained as 2,22% from the ZE-1F SAM molecules. The best 2,0% efficiency is obtained from ITO/TiO2/P3HT:PCBM/MoO3/Ag inverted type solar cells structures that use SAM molecules ITO/TiO2/SAM/P3HT: PCBM/ MoO3/Ag structure was obtained higher efficiencies. The highest efficiency value was obtained as 2,43% from the MK120 SAM molecules. 117

Published
2016

24. Flame-retardant treatment of wool and wool-rich blends: A study of bath composition.

Author

Kaynak, Elif, Üreyen, Mustafa Erdem, Koparal, Ali Savaş, and Mutlu, Adem

Abstract

Wool and wool-polyamide blended yarns (88.6% wool–11.4% polyamide 6,6 and 78.5% wool–21.5% polyamide 6,6) were knitted and the produced fabrics were treated by exhaustion method with zirconium complexes. Six different baths containing potassium hexafluorozirconate and zirconium acetate were studied. The flammability hazard was evaluated considering parameters such as the spread of flame, the heat release and the smoke release rate. Regardless of the blend composition, the untreated fabrics could not pass the vertical flammability test. 100% wool fabric could pass the vertical flammability test when treated with only 1% potassium hexafluorozirconate and 10% zirconium acetate solution. Higher compositions of metal complexes were required for the blended fabrics to pass the vertical flammability test. In the cone calorimeter test, 100% wool treated with 5% potassium hexafluorozirconate and 10% zirconium acetate solution gave the lowest peak heat release and smoke release rate values as 146.4 kW/m2 and 1.2 s−1, respectively. [ABSTRACT FROM AUTHOR]

Published
2021
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25. Büyükşehir belediyelerinde yeni hizmet yöntemleri: İstanbul Otobüs A.Ş. örneği

Author

Mutlu, Adem, Ateş, Hamza, and Siyaset Bilimi ve Kamu Yönetimi Ana Bilim Dalı

Subjects
Kamu Yönetimi, Service quality, Public Administration, Public services, Local administrations, Metropolitan municipality, Istanbul, Istanbul Metropolitan Municipality, Service production, Service providence, Municipalities
Abstract

Türkiye'de kamu hizmetleri sunumunda yerel yönetimler hizmetlerin halka ulaştırılmasında etkin ve önemli rol oynamaktadır. Kamu yönetiminde değerler dizisi değişimi ile yerel yönetimlerden beklentilerin her geçen gün daha üst seviyelere çıkması sebebiyle belediyelerin içinde bulunulan çağın standartlarını yakalama hususunda çalışmalar yapması kaçınılmaz olmuştur. Hal böyle olunca da yerel yönetimlerin vatandaşların ihtiyaçlarını karşılama konusunda yeni hizmet sistemleri geliştirme çabası içine girdikleri görülmektedir.İstanbul Büyükşehir Belediyesi (İBB), kanunların kendisine verdiği yetkiye dayanarak hizmet sunmak, hizmet sunacak kurumdan hizmet satın almak veya şirket kurup işletmek konularında yetki sahibidir. Bu yetkiye dayanarak İBB, belediyenin görevlerinden olan toplu ulaşım hizmetlerini iyileştirmek için bu alanda hizmet veren İETT ve Özel Halk Otobüslerinden (ÖHO) farklı, yeni bir hizmet modeli geliştirerek İstanbul Otobüs A.Ş. kurmuştur. Şirketin faaliyetleri ve söz konusu faaliyetlerin belediyenin kuruluş amacına hizmet edip etmediğinin ortaya çıkarılmasının amaçlandığı bu çalışmada yapılan araştırmalar neticesinde görüldüğü üzere, İstanbul Otobüs A.Ş. 'nin gerçekleştirdiği faaliyetler yeni bir hizmet modeli olarak değerlendirilebilir. Şirket, İETT'den ve benzer hizmet sunan özel halk otobüsü işletmelerinden verimlilik, dezavantajlı gruplara hizmetlerin ulaştırılması ve kaliteli/konforlu hizmet sunma, aktif yönetim ve dinamik yönetim, hızlı karar alma ve uygulama konularında diğer kurumlardan önde seyrettiği gözlemlenmiştir. Şirketin bunları sağlarken, -kamu kurumu olmalarına rağmen- faaliyetler sonunda kar elde etmesi de dikkate değer bir noktadır. Bunun yanında kalite yönetim sistemi, stratejik plan gibi kurumsallaşma adına bazı uygulamaların olmaması ve şirketin diğerlerine göre göre yeni olmasından kaynaklanan tecrübe eksikliği şirketin eksi yönleri arasında sıralanabilir. The local administrations in Turkey, has been effective and productive in administering and providing services of the public utilities regarding transmitting to the public sphere. By reason of the paradigm shift in public administration and increasing of the expectations day by day from local administrations, it is necessary to carry out studies for municipalities in order to catching the standards of the time. It's a well-known that under these circumstances the local administrations go into the effort of supplying demands of citizens. Istanbul Metropolitan Municipality (İBB) carries authority in areas of performing services to the public, buying services from related corporations, and establishing and operating a company. By this authorization, for developing the transportation services which is also duty of the municipality, the municipality has based a bus corporation as called `Otobüs A.Ş.`. It has been established as different model of service from IETT and Özel Halk Otobüsü (ÖHO) in order to make public transportation services better. As it is seen in consequence of the thesis which has aimed to find out the operations of the company (Otobüs A.Ş.) and reveal whether these operations serve the purpose, services of the company can be evaluated as a new service model. During the thesis, it has been observed that the company is in advance over IETT and other ÖHO in view of the efficiency, satisfaction of citizens, delivering services to disadvantageous groups, with higher quality and more comfortable. Whilst the company is providing these, although being a public corporation, it is noteworthy point that the company make profit in result of these operations. Besides, it's not having significant institutionalization bodies such as strategic planning and quality managing system can be formed as and lack of experience, negative dimensions of the company. 181

Published
2015

26. Double connector to TiO2 surface in small molecule triphenyl amine dyes for DSSC applications.

Author

Özkan, Eren, Mutlu, Adem, Zafer, Ceylan, and Dinçalp, Haluk

Subjects
TRIPHENYLAMINE, SMALL molecules, FLUORESCENCE yield, DYE-sensitized solar cells, ORGANIC dyes, DYES & dyeing
Abstract

Two novel dyes 3a and 3b named triphenylamine groups containing donor–acceptor structural units have been explored to be used in dye sensitized solar cells as organic sensitizers. The absorption bands of the dyes were extended up to ~ 550 nm with visible absorption maxima at 408–430 nm and optical band gaps of 2.44–2.47 eV. Compared to the methoxyphenyl-substituted dye, the introduction of triisopropylphenyl group instead of that increased fluorescence quantum yields and exhibited red-shift emission in chloroform. We have investigated the photovoltaic properties of DSSCs based on these metal free organic dyes. It has been found that the power conversion efficiency of DSSCs sensitized with methoxyphenyl based triphenylamine dye is higher than that for sensitized with triisopropylphenyl derivative. [ABSTRACT FROM AUTHOR]

Published
2019
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