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Aluminum-Induced crystallization: Applications in photovoltaic technologies
(Pan Stanford Publishing Pte. Ltd., 2014) Slaoui, Abdelilah; Pathi, Prathap; Özmen, Özge Tüzün
[No abstract available]
Comparison of Different Types of Photovoltaic Solar Panels' Performance and Efficiency for Düzce from 2014 to 2019 Years Summertime
(Düzce Üniversitesi, 2023) Özdemir, Tuğba; Özmen, Özge Tüzün
Technology, which is indispensable in the modern world, has made human beings dependent on energy. Much of the world’s global energy comes from fossil fuels which are harmful to people and the environment and also really expensive. Those negativities push the nations to investigate new energy sources and have in have increased the interest and investment in renewable energy. Solar energy is one of the most environmentally friendly, abundant, cheap and healthy natural energy sources. A study has been started in Düzce University to benefit from solar energy in order to contribute to our country and the world. Düzce University Scientific and Technological Research Application and Research Center (DUBIT) installed three photovoltaic panels of amorphous silicon (a-Si), polycrystalline silicon (pc-Si), and monocrystalline silicon (mc-Si). The three installed panels produce a total power of 7.5 kW such that 2.5 KW of power are produced by each panel independently. In this study, the efficiency, performance, radiation, and total daily energy values generated by the photovoltaic panels used, based on the summer months (May, June, July, August) for the years 2014 to 2019, six-years analyses were completed. According to the analyses and calculations carried out, the performance and efficiency of the panels over the years were evaluated in the climatic conditions of Düzce. Analysis of the results obtained, it was concluded that the PV panel m-Si is the highest type of panel with an efficiency of 12.8% and performance of 87.6%. Furthermore, it was observed that the summer months of 2015 were the year in which all photovoltaic panels operated with the highest efficiency.
Dielectric and Performance Analysis of CdTe Quantum Dots Doped Nematic Liquid Crystal
(2018) Özmen, Özge Tüzün; Önsal, Gülnur; Yıldırım, Mert; Kocakülah, Gülsüm; Köysal, Oğuz
Bu çalışmada çekirdek tipi kadmiyum tellür kuantum noktaları (CdTe QDs) ağırlıkça % 0,05 oranında 5CB (4pentil-4'-siyanobifenil) nematik sıvı kristale (LC) katkılanmış ve dielektrik özellikleri 100 Hz-10 MHz frekans aralığında empedans ölçümleri kullanılarak araştırılmıştır. CdTe kuantum noktaların 5CB nematik sıvı kristal yapıda gösterdiği etkiyi belirlemek için dielektrik anizotropi (??), geçiş frekansı (fgeçiş), kritik frekans (fkritik), dielektrik sabiti (?' ve ?") değerleri saf ve CdTe katkılı LC için deneysel veriler kullanılarak elde edilmiştir. Ayrıca, eşik voltajı (Vth) ve eğilme elastik sabiti (K11) hesaplanmıştır. CdTe katkılanmasıyla eşik voltajı (Vth) ve eğilme elastik sabitinin (K11) önemli ölçüde azaldığı görülmüştür
Effects of glass substrate coated by different-content buffer layer on the quality of poly-Si thin films
(Wiley-V C H Verlag Gmbh, 2016) Karaman, Mehmet; Özmen, Özge Tüzün; Sedani, Salar Habibpur; Özkol, Engin; Turan, Raşit
In this work, polycrystalline silicon (poly-Si) thin films were fabricated by aluminum induced crystallization (AIC) technique. SiNx, deposited as a function of NH3/SiH4 ratio, and AZO (Al-doped ZnO) films on glass were used as a buffer layer between glass and Si film. The effect of buffer layer content on the crystallinity of poly-Si thin films was studied by Raman analysis which shows that fully crystallization without stress was achieved for all samples. Moreover, the preferred crystalline orientation and crystallite size of films were deduced by X-ray diffraction (XRD) analysis. The preferred orientation is <100> as independent from the buffer layer content while the crystallite sizes increase up to 48.5 nm by increasing the amount of SiH4. The electrical properties of the films were carried out by four point probe and currentvoltage (I-V) analysis. Both techniques demonstrated that the resistivity of the SiNx-based samples is around 0.1Ocm. The grain size analysis was accomplished by electron back scattering diffraction (EBSD) measurements. The grain size up to 25 mu m was achieved as observed from EBSD images. The results show that the fabrication parameters of SiNx and AZO buffer layers have the great effects on the crystallography of poly-Si films. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Effects of PCBM concentration on the electrical properties of the Au/P3HT:PCBM/n-Si (MPS) Schottky barrier diodes
(Pergamon-Elsevier Science Ltd, 2014) Özmen, Özge Tüzün
In this study, the gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/n-type silicon (Au/P3HT:PCBM/n-Si) metal-polymer-semiconductor (MPS) Schottky barrier diodes (SBDs) were investigated in terms of the effects of PCBM concentration on the electrical parameters. The forward and reverse bias current-voltage (I-V) characteristics of the Au/P3HT:PCBM/n-Si MPS SBDs fabricated by using the different P3HT:PCBM mass ratios were studied in the dark, at room temperature. The main electrical parameters, such as ideality factor (n), barrier height (Phi(B0)), series resistance (R-s), shunt resistance (R-sh), and density of interface states (N-ss) were determined from I-V characteristics for the different P3HT:PCBM mass ratios (2:1, 6:1 and 10:1) used diodes. The values of n, R-s, Phi(B0), and N-SS were reduced, while the carrier mobility and current were increased, by increasing the PCBM concentration in the P3HT:PCBM organic blend layer. The ideal values of electrical parameters were obtained for 2:1 P3HT:PCBM mass ratio used diode. This shows that the electrical properties of MPS diodes strongly depend on the PCBM concentration of the P3HT:PCBM organic layer. Moreover, increasing the PCBM concentration in P3HT:PCBM organic blend layer improves the quality of the Au/P3HT:PCBM/n-Si (MPS) SBDs which enables the fabrication of high-quality electronic and optoelectronic devices. (C) 2014 Elsevier Ltd. All rights reserved.
Electrical and interfacial properties of Au/P3HT:PCBM/n-Si Schottky barrier diodes at room temperature
(Elsevier Sci Ltd, 2014) Özmen, Özge Tüzün; Yağlıoğlu, E.
In this study, a gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/n-type silicon (Au/P3HT:PCBM/n-Si) metal-polymer-semiconductor (MPS) Schottky barrier diode (SBD) was fabricated. To accomplish this, a spin-coating system and a thermal evaporation were used for preparation of a P3HT/PCBM layer system and for deposition of metal contacts, respectively. The forward- and reverse-bias current-voltage (I-V) characteristics of the MPS SBD at room temperature were studied to investigate its main electrical parameters such as ideality factor (n), barrier height (phi(B)), series resistance (R-s), shunt resistance (R-sh), and density of interface states (N-ss). The I-V characteristics have nonlinear behavior due to the effect of R-s, resulting in an n value (3.09) larger than unity. Additionally, it was found that n, phi(B), R-s, R-sh, and N-ss have strong correlation with the applied bias. All results suggest that the P3HT/PCBM interfacial organic layer affects the Au/P3HT:PCBM/n-Si MPS SBD, and that R-s and N-ss are the main electrical parameters that affect the Au/P3HT:PCBM/n-Si MPS SBD. Furthermore, a lower N-ss compared with that of other types of MPS SBDs in the literature was achieved by using the P3HT/PCBM layer. This lowering shows that high-quality electronic and optoelectronic devices may be fabricated by using the Au/P3HT:PCBM/n-Si MPS SBD. (C) 2014 Elsevier Ltd. All rights reserved.
Estimating Energy Production of Solar Power Plant at the University of Bakırçay Using Artificial Neural Networks Based on Meteorological Conditions
(İzmir Bakırçay Üniversitesi, 2022) Uz, Özgün; Özdemir, Tuğba; Özmen, Özge Tüzün
The rapid depletion of fossil fuels and environmental concerns have led people to work on renewable energy sources. In order to leave a cleaner and more liveable world for future generations and enable developed countries to produce more economical energy using their own resources, major investments have been made in renewable energy resources. Photovoltaic (PV) energy has a large share among renewable energy sources. Turkey has taken its place among the countries that are aware of the PV energy potential and invest in this field. The ratio of installed PV energy power to total installed power is also increased day by day in Turkey. However, meteorological factors affecting PV energy production make it difficult to compute energy production in advance. In this study, the relationship between meteorological data and power generation data was analyzed using the power generation data of the solar power plant (SPP) with an installed power of 400 kW in the student car park of the University of Bakırçay and the meteorological data of the province of İzmir. As a result of the comparison of the tests, energy production with respect to meteorological factors achieve a remarkable success rate with 95.3% when artificial neural networks are employed.
F4-TCNQ concentration dependence of the current-voltage characteristics in the Au/P3HT:PCBM:F4-TCNQ/n-Si (MPS) Schottky barrier diode
(Iop Publishing Ltd, 2014) Yağlıoğlu, E.; Özmen, Özge Tüzün
In this study, we investigate some main electrical parameters of the gold/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester:2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane/n-type silicon (Au/P3HT:PCBM:F4-TCNQ/nSi) metal-polymer-semiconductor (MPS) Schottky barrier diode (SBD) in terms of the effects of F4-TCNQ concentration (0%, 1%, and 2%). F4-TCNQ-doped P3HT:PCBM is fabricated to figure out the p-type doping effect on the device performance. The main electrical parameters, such as ideality factor (n), barrier height (Phi(B0)), series resistance (R-s), shunt resistance (R-sh), and density of interface states (N-ss) are determined from the forward and reverse bias current-voltage (I-V) characteristics in the dark and at room temperature. The values of n, R-s, Phi(B0), and N-ss are significantly reduced by using the 1% F4-TCNQ doping in P3HT:PCBM:F4-TCNQ organic blend layer, additionally, the carrier mobility and current are increased by the soft (1%) doping. The most ideal values of electrical parameters are obtained for 1% F4-TCNQ used diode. On the other hand, the carrier mobility and current for the hard doping (2%) become far away from the ideal diode values due to the unbalanced generation of holes/electrons and doping-induced disproportion when compared with 1% F4-TCNQ doping. These results show that the electrical properties of MPS SBDs strongly depend on the F4-TCNQ doping and doping concentration of interfacial P3HT:PCBM:F4-TCNQ organic layer. Moreover, the soft F4-TCNQ doping concentration (1%) in P3HT:PCBM:F4-TCNQ organic layer significantly improves the electrical characteristics of the Au/P3HT:PCBM:F4-TCNQ/n-Si (MPS) SBDs which enables the fabricating of high-quality electronic and optoelectronic devices.
Farklı Üretim Parametrelerinin Katı Faz Kristalizasyon (SPC) Tekniği Kullanılarak Üretilen Polikristal Silisyum İnce Filmlerin Kalitesi Üzerine Etkileri
(Gazi Univ, 2019) Özmen, Özge Tüzün; Sedani, Salar Habibpur; Karaman, Mehmet; Gökşen, Kadir; Turan, Raşit
Yüksek elektronik kaliteleri ve optimize edilmiş eklem yapıları nedeniyle SiNx kaplı cam alttaş üzerindeki polikristal silisyum (poly-Si) ince filmler, hacimsel silisyum bazlı güneş hücrelerine karşı umut vaat edici alternatif yaklaşımlardır. Bu çalışmada, poly-Si filmler katı faz kristalizasyonu (SPC) tekniği ile üretilmişlerdir. Filmler, klasik tüp fırında 600oC’de 8-26 saat aralığında kristalleştirilmişlerdir. SiNx kaplı cam alttaş üzerindeki poly-Si ince filmlerin yapısal ve optiksel özellikleri araştırılmıştır. Poly-Si ince filmlerin yönelimi ve kristalit büyüklüğü X-ışını kırınımı (XRD) kullanılarak incelenirken filmlerin kristallenme derecesi mikro Raman spektroskopisi ile çalışılmıştır. Kristalizasyon süresinin filmin kalitesi üzerine önemli etkileri olduğu bulunmuştur. Deneyler sonucunda, tavlama süresi 8 saatten 26 saate arttırıldığında kristallenme derecesinin %10’dan %95’e arttığını göstermiştir. 600oC’de kristallenen SPC poly-Si filmlerin tercihli yönelimi tüm tavlama zamanları için <111>’dir. Diğer yandan, artan tavlama süresi kristalit boyutunu 29,6nm’den 36,3nm’e büyütmüştür. Bu analizlere ek olarak, bu çalışmada, e-demeti sistemi ile büyütülen a-Si’un üretim esnasında kullanılan potanın SPC poly-Si filmin kristal kalitesi üzerine etkileri de araştırılmıştır. Sonuçlar göstermiştir ki e-demeti sisteminde kullanılan potanın malzemesinin grafit yerine molibden (Mo) olması gerektiği ve SPC tekniğini ile oluşturulan poly-Si filmlerin kalitesi üzerine önemli etkisi olduğu görülmüştür.
Farklı Üretim Parametrelerinin Katı Faz Kristalizasyon (SPC) Tekniği Kullanılarak Üretilen Polikristal Silisyum İnce Filmlerin Kalitesi Üzerine Etkileri
(2019) Özmen, Özge Tüzün; Sedani, Salar Habibpur; Karaman, Mehmet; Gökşen, Kadir; Turan, Raşit
Yüksek elektronik kaliteleri ve optimize edilmiş eklem yapıları nedeniyle SiNx kaplı cam alttaş üzerindeki polikristal silisyum (poly-Si) ince filmler, hacimsel silisyum bazlı güneş hücrelerine karşı umut vaat edici alternatif yaklaşımlardır. Bu çalışmada, poly-Si filmler katı faz kristalizasyonu (SPC) tekniği ile üretilmişlerdir. Filmler, klasik tüp fırında 600oC’de 8-26 saat aralığında kristalleştirilmişlerdir. SiNx kaplı cam alttaş üzerindeki poly-Si ince filmlerin yapısal ve optiksel özellikleri araştırılmıştır. Poly-Si ince filmlerin yönelimi ve kristalit büyüklüğü X-ışını kırınımı (XRD) kullanılarak incelenirken filmlerin kristallenme derecesi mikro Raman spektroskopisi ile çalışılmıştır. Kristalizasyon süresinin filmin kalitesi üzerine önemli etkileri olduğu bulunmuştur. Deneyler sonucunda, tavlama süresi 8 saatten 26 saate arttırıldığında kristallenme derecesinin %10’dan %95’e arttığını göstermiştir. 600oC’de kristallenen SPC poly-Si filmlerin tercihli yönelimi tüm tavlama zamanları için <111>’dir. Diğer yandan, artan tavlama süresi kristalit boyutunu 29,6nm’den 36,3nm’e büyütmüştür. Bu analizlere ek olarak, bu çalışmada, e-demeti sistemi ile büyütülen a-Si’un üretim esnasında kullanılan potanın SPC poly-Si filmin kristal kalitesi üzerine etkileri de araştırılmıştır. Sonuçlar göstermiştir ki e-demeti sisteminde kullanılan potanın malzemesinin grafit yerine molibden (Mo) olması gerektiği ve SPC tekniğini ile oluşturulan poly-Si filmlerin kalitesi üzerine önemli etkisi olduğu görülmüştür.
Fotovoltaik Enerji Üretiminin Meteorolojik Şartlarla İlişkilendirilmesi: İzmir Bakırçay Üniversitesi Örneği
(Burdur Mehmet Akif Ersoy University, 2022) Uz, Özgün; Özdemir, Tuğba; Özmen, Özge Tüzün
Türkiye, güneş enerjisi potansiyeli yüksek bir coğrafi bölgede yer almaktadır. Güneş potansiyelini yüksek kılan meteorolojik faktörler, elektrik üretimini doğrudan etkilemektedir. Mevcut üreticiler için öngörülen meteorolojik şartlardaki elektrik üretimi tahmin etmek üretim planlaması yapmaya yardımcı olacaktır. Aynı zamanda yatırımcılar için farklı bölgelerde yapılacak yatırımlarda güç çıkışını önceden tahmin etmek teşvik edici olacaktır. Bu çalışmada İzmir Bakırçay Üniversitesi bünyesinde bulunan 400kW güce sahip güneş enerji santralinin 2020 yılına ait üretim verileri, İzmir Meteoroloji Bölge Müdürlüğü’nden elde edilen meteorolojik verilerle birlikte analiz edilmiş ve aylık periyotlarda karşılaştırılması yapılmıştır. Üretilen elektrik enerjisindeki değişimin meteorolojik faktörlerle ilişkilendirilerek açıklanmasıyla birlikte ilerde yapılacak üretimde ve yatırımlarda yol gösterici olması amaçlanmıştır.
Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode
(Springer, 2017) Taşçıoğlu, İlke; Özmen, Özge Tüzün; Şağban, Muzaffer; Yağlıoğlu, E.; Altındal, Ş.
In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage (C-V) and conductance-voltage (G/omega-V) measurements in the frequency range of 10 kHz-2 MHz. The C-V-f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states (N (ss)). The values of N (ss) located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant (epsilon') and dielectric loss (epsilon aEuro(3)) decrease with increasing frequency, whereas loss tangent (tan delta) remains nearly the same. The decrease in epsilon' and epsilon aEuro(3) was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity (sigma (ac)) and electric modulus (M' and MaEuro(3)) increase with increasing frequency.
High work-function hole transport layers by self-assembly using a fluorinated additive
(Royal Soc Chemistry, 2014) Mauger, Scott A.; Li, Jun; Özmen, Özge Tüzün; Yang, Andy Y.; Friedrich, Stephan; Rail, M. Diego; Moule, Adam J.
The hole transport polymer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) derives many of its favorable properties from a PSS-rich interfacial layer that forms spontaneously during coating. Since PEDOT: PSS is only usable as a blend it is not possible to study PEDOT: PSS without this interfacial layer. Through the use of the self-doped polymer sulfonated poly(thiophene-3-[2-(2-methoxyethoxy) ethoxy]-2,5-diyl) (S-P3MEET) and a polyfluorinated ionomer (PFI) it is possible to compare transparent conducting organic films with and without interfacial layers and to understand their function. Using neutron reflectometry, we show that PFI preferentially segregates at the top surface of the film during coating and forms a thermally-stable surface layer. Because of this distribution we find that even small amounts of PFI increase the electron work function of the hole transport layer. We also find that annealing at 150 degrees C and above reduces the work function compared to samples heated at lower temperatures. Using near edge X-ray absorption fine structure spectroscopy and gas chromatography we show that this reduction in work function is due to S-P3MEET being doped by PFI. Organic photovoltaic devices with S-P3MEET/PFI hole transport layers yield higher power conversion efficiency than devices with pure S-P3MEET or PEDOT: PSS hole transport layers. Additionally, devices with a doped interface layer of S-P3MEET/PFI show superior performance to those with un-doped S-P3MEET.
Investigation of photoinduced change of dielectric and electrical properties of indium (III) phthalocyanine and fullerene doped nematic liquid crystal
(Elsevier Science Sa, 2012) Özmen, Özge Tüzün; Gökşen, Kadir; Demir, Ahmet; Durmuş, Mahmut; Köysal, Oğuz
In this work, we have studied photoinduced dielectric and electrical properties of E63 nematic liquid crystal (E63-LC) materials doped with indium (III) metallo phthalocyanine (In-MPc) and fullerene (C-60) in dark and under UV illumination. Doping concentration of In-MPc in E63-LC was chosen to be 5 wt%, whereas a trace amount of C-60 was used in investigated samples. Real and imaginary parts of dielectric permittivity were investigated in the frequency range of 100 Hz-10 MHz by using dielectric spectroscopy technique (DST). It was observed that doping agents and UV illumination enhanced the real part of dielectric permittivity at low frequencies, which was thought to originate from photoinduced charge transfer between In-MPc and C-60 caused by extra dipole strength in LC medium. In addition to that, critical frequency (f(c)) and relaxation time (tau) were obtained and analyzed for all investigated samples. Photoelectrical characteristics of hybrid LC structures were carried out by current voltage measurements. A major increase in electrical conductivity was observed in In-MPc and C-60 doped LC structures under UV irradiation. (C) 2012 Elsevier B.V. All rights reserved.
Outdoor performance analysis of different PV panel types
(Pergamon-Elsevier Science Ltd, 2017) Elibol, Erdem; Özmen, Özge Tüzün; Tutkun, Nedim; Köysal, Oğuz
Photovoltaic (PV) panel efficiency has been tested in the laboratory at standard test conditions (STC) (25 degrees C, 1000 W/m(2) and AM:1.5). However, PV panels are used in different regions and climatic conditions quite different from STC. Due to that, panel efficiency is not observed same with manufacturer catalogue data. This study focus on outdoor testing of PV panels performances at literature, in addition, one-year results of mono-crystalline (2.35 kW), polycrystalline (2.64 kW) and amorphous silicon (2.40 kW) photovoltaic panels were analysed. These PV panels were placed on the roof of Duzce University Scientific and Technological Researches Application and Research Centre (DUBIT) in Duzce Province, in Turkey, one of the countries with the highest solar power potential in Europe and connected to power grid. Amounts of energy produced by the panels over a day, a month and a year as well as inverter efficiency and performance ratios were calculated. Performance ratios were found out as 73%, 81% and 91% for a-Si, polycrystalline and mono-crystalline PV panels, respectively. Panel efficiency was calculated as 4.79%, 11.36% and 13.26% in the same order. All results were compared with Previous studies. Statistical analysis was made to state relationship between efficiency and performance ratios of panel types, environmental temperature, panel temperature and amount of radiation. As a result of the statistical analysis, it was observed that temperature increase of 1 degrees C increased the efficiency of a-Si panels 0.029% and the efficiency of polycrystalline panels 0.033%, yet, decreased the efficiency of mono-crystalline panels 0.084%. (C) 2016 Elsevier Ltd. All rights reserved.
PCDTBT:PCBM Tabanlı Organik Schottky Diyotlarının ve Heteroeklem Güneş Hücrelerinin Optoelektronik Karakterizasyonu
(2019) Gökşen, Kadir; Kurtay, Merve Zayim; Özmen, Özge Tüzün; Şağban, Muzaffer; Köysal, Oğuz
Bu çalışmada Gümüş/n-tipi Silisyum/poly[N-9?-heptadecanyl-2,7–carbazole–alt-5,5-(4?,7?-di–2–thienyl-2?,1?,3?-benzothiadiazole:[6,6]-phenyl-C61-butyric acid methyl ester/Altın (Ag/n-Si/PCDTBT:PC61BM/Au) organik metalpolimer yarıiletken Schottky bariyer diyotları, polimer arayüz olarak %20 PCDTBT ve %80 PCBM karışımı kullanılaraküretilmiştir. Üretilen diyotların 240 - 350 K sıcaklık aralığında akım-voltaj ölçümleri yapılarak, bu sıcaklıklardaki diyotidealite faktörü değerlerinin 1,80 ve 2,26 aralığında değiştiği gözlemlenmiştir. Çalışmanın ikinci aşamasında, İndiyumKalay Oksit/PCDTBT:PCBM/Gümüş (ITO/PCDTBT:PCBM/Ag) organik güneş hücresi %20:%80 PCDTBT:PCBMhacimsel oranına sahip olacak şekilde üretilmiş ve güç dönüştürme verimi % 0,85 olarak bulunmuştur.
Polysilicon thin films fabricated by solid phase crystallization using reformed crystallization annealing technique
(Elsevier Science Sa, 2014) Özmen, Özge Tüzün; Karaman, Mehmet; Turan, Raşit
In this work, a reformed crystallization annealing technique is presented for the solid phase crystallization (SPC) of amorphous silicon (a-Si) on SiNx-coated quartz substrate. This technique includes a two-step annealing process which consists of a low-temperature (475 degrees C) classical furnace annealing for nucleation of Si and a high-temperature (900 degrees C) grain growth process of polycrystalline silicon (poly-Si) during thermal annealing in classical tube furnace. The aim of this reformed two-step annealing technique is reducing the long (up to 48 h) crystallization annealing duration of single step annealing at low temperatures (similar to 600 degrees C) while maintaining the film quality, as low-temperature single step annealing, by using reformed technique. Continuous p-type poly-Si film was formed on quartz substrate thanks to exodiffusion of boron, which was deposited prior to a-Si, through Si film by thermal annealing. The stress and degree of crystallinity of the p-type poly-Si were studied by the micro-Raman Spectroscopy. The crystallization fraction value of 95% was deduced for annealed samples at 900 degrees C, independent from crystallization technique. On the other hand, the Raman analysis points out that compressive stress was induced by increasing the annealing duration at 900 degrees C. X-ray diffraction (XRD) analysis reveals that the preferred crystallite orientation of the films, independent from crystallization temperature and substrates, is < 111 >. Additionally, the average crystallite size calculated from XRD patterns increases from 69 angstrom to 165 angstrom by using reformed two-step annealing instead of single step annealing at 900 degrees C for 90 min. The exodiffusion of boron into the silicon film was deduced from secondary ion mass spectrometry (SIMS) analysis and the p(+)/p graded boron profile was obtained, which may result higher carrier diffusion length and longer carrier life time. Finally, the annealing duration dramatically decrease to 9 h by using reformed two-step annealing technique instead of conventional single step annealing at 600 degrees C. The results show that reformed SPC annealing technique has major advantages by combining the lower annealing duration and high crystal quality. (C) 2013 Elsevier B. V. All rights reserved.
Solid phase epitaxial thickening of boron and phosphorus doped polycrystalline silicon thin films formed by aluminium induced crystallization technique on glass substrate
(Elsevier Science Sa, 2019) Özmen, Özge Tüzün; Karaman, Mehmet; Sedani, Salar Habibpur; Sagban, H. Muzaffer; Turan, Raşit
Aluminium induced crystallization (AIC) technique can be used to form the high-quality and large-grained polycrystalline silicon (poly-Si) thin films, which are with the thickness of similar to 200 nm and used as a seed layer, on silicon nitride coated glass substrate. Thanks to aluminium metal in AIC process, the natural doping of AIC thin films is p(+) type (similar to 2 x 10(18) cm(-3)). On the other hand, recombination of carriers can be controlled by partial doping through the defects that may have advantages to improve the thin film quality by the overdoping induced passivation. In this study, boron (B) and phosphorus (P) doped AIC seed layers were thicken to similar to 2 mu m by solid phase epitaxy (SPE) technique at 800 degrees C for 3 h under nitrogen flow in a tube furnace. During the crystallization annealing, exodiffusion of dopants was formed through the SPE film from the AIC seed layer. Optical microscope and electron back scattering diffraction technique (EBSD) were used to analyse the structural quality of the Si films. The poly-Si layer with an average grain size value of similar to 32 mu m was formed by AIC + SPE technique for P doped samples while EBSD analysis gave no results for B doped samples due to the quite deterioration on the surface of the films. AIC + SPE films were analyzed in terms of structural properties by using micro-Raman Spectroscopy and X-ray diffraction systems. The results showed that the crystallinity of compressive stress formed AIC + SPE films reached up to 98.55%. Additionally, the Raman analysis pointed out that no temperature-induced stress were generated in the AIC + SPE films while compressive stress was induced by increasing the annealing duration for doped AIC film. For all samples, the preferred orientation was < 100 >, and the crystallite size up to 44.4 nm was formed by phosphorus doping of AIC films. The doping efficiency was determined by time-of-flight secondary ion mass spectroscopy for doped samples. A graded n(+)n doping profile was obtained by exo-diffusion of phosphorus from the overdoped seed layer during the epitaxial thickening while boron doping of SPE film has failed with exo-diffusion of boron from AIC seed layer into SPE film. Finally, high-quality n(+)n type poly-Si films were fabricated on glass substrate by using AIC + SPE technique.
Synthesis and Optoelectronic Properties of Pyrite (FeS2) Nanocrystals Thin Films for Photovoltaic Applications
(Amer Scientific Publishers, 2013) Kılıç, Bayram; Roehling, John; Özmen, Özge Tüzün
Nanocrystal (NCs) pyrite FeS2 were synthesized on indium thin oxide (ITO) substrate by using thermal reaction of iron-oleyamine complexes with sulfur in olayamine. The structural and optical characterizations of FeS2 NCs were investigated and the effect of annealing temperature on thin film properties was discussed. The Scanning Electron Microscope (SEM) images shows that FeS2 films have between 25 nm and 100 nm diameter and as the annealing temperature on the thin film increased, the particle size increased. The absorption spectrums show that FeS2 NCs have direct band gap between 1.27 and 2.04 eV which is much higher than that of bulk FeS2 (0.95 eV). The changes of particle size can be attributed to the different interactions of surface energy and interface energy at different annealing temperatures. Current-Voltage characteristics show that NCs FeS2 has high conductivity and it was found that when annealing temperature of thin films increases, conductivity decreases. The surface photo voltage (SPVs) of FeS2 films was studied to explore their potential in photovoltaic application as well.

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