Advanced plasmonic interfaces for optimized light trapping in photovoltaics

Plasmonic interfaces are integrated to photovoltaic devices to enhance light trapping and improve efficiency. The optimum thickness of the spacer layer used to passivate the absorber layer and adjust its distance from the metal nanoparticles remains unclear. We integrate plasmonic interfaces consisting of Ag nanoparticles and silicon nitride spacers of different thicknesses to the back of a-Si:H absorber to investigate the optimum thickness of the spacer layer and use the photocurrent in a-Si:H to indicate the enhancement in light-trapping. For integration to the back or front of the device, the localized surface plasmon resonance (LSPR) is shifted and broadened into the red with increased spacer layer thickness and the effect is more pronounced for integration to the back. An appreciable enhancement of photocurrent in a-Si:H is consistent with this broadening of LSPR and has a critical dependence on spacer layer thickness

Bor nitrür üretimi

TÜBİTAK MAG15.04.2008Bor nitrür, grafite çok benzer altıgen (h-BN) yapıda tabakalar halinde veya kübik yapıda (k- BN) elmasa çok yakın özelliklerde bulunabilir. k-BN bilinen malzemeler içinde elmastan sonra en sert olduğundan malzeme endüstrisinde sert metal kaplamalar yapmada (elmastan daha üstün özelliklerde, metal işlemede) kullanılmaktadır. Ayrıca, elmas sadece p-türü katkılanabildiği halde, k-BN hem p hem de n türü katkılanabilmektedir, ve dolayısıyla elektronik devrelerin yapı taşı olan p-n eklemini üretmek olası olduğundan mor-mavi ışık bölgesinde ışık algılayıcısı (detektör) ve yayınlayıcısı (LED) uygulamasına açıktır. k-BN tabanlı bu devre elemanlarının, opto-elektronik yatkınlıkları yanında, elmastan daha yüksek bir yasak enerji aralığına sahip olmalarından dolayı çok daha yüksek sıcaklık ortamlarında kullanılmalarını sağlanabilir. Son yıllarda yapılan araştırmalar k-BN’nin plazma ortamında Fiziksel Buhar Biriktirme (FBB) veya Kimyasal Buhar Biriktirme (KBB) yöntemleri ile üretilebileceğini göstermiştir. Ancak bu çalışmalar biriktirilen maddenin özelliklerine (k-BN içeriği ve mekanik gerilim) ve birikme hızına etki eden üretim parametrelerinin (kullanılan bor ve azot kaynakları, kullanılan gaz kompozisyonu, kaplanan yüzeyi oluşturan madde(taban), uygulanan plazma yoğunluğu, RF gücü, bias voltaj, taban sıcaklığı) nasıl etki ettiğini sistematik bir yaklaşımla incelememiştir. Elde, çevre birimleriyle birlikte, kurulu bulunan hem FBB, hem de KBB düzenekleriyle (yapılabilir bazı değişiklikler ve eklerle), yukarıda sözü edilen sistematik çalışma olanaklar çerçevesinde gerçekleştirilmiştir. Başka bir deyişle hem RF hem de MW kullanan KBB ve magnetron çığlama kullanan KBB teknikleriyle büyütülen filmler, eldeki ve proje bütçesiyle sağlanan olan ölçüm/test düzenekleriyle çözümlenmiştir. Böylece üretim test döngüsü yinelenerek hedeflenen mekanik ve opto-elektronik özellikte k-BN ince filmleri ve ondan üretilebilecek yapıları oluşturan en uygun üretim koşulları belirlenmeye çalışılmıştır.Boron nitride can be found in hexagonal structure (hBN) which is very much like graphite or in cubic structure with properties very close to those of diamond. Since cBN is the hardest known material after diamond is used in making hard metal covers (used in metal machining with superior properties to diamond). In addition, while diamond can be doped only in p type both p and n type doping is possible in cBN, therefore cBN can be used to make p-n junction which is a basic part of the microelectronic circuits. That means cBN can be used to make a detector or Light Emitting Diode (LED) in violet-blue region. In addition to these optoelectronic properties, cBN based circuit parts are expected to withstand very high temperatures due to the higher forbidden energy gap of cBN compared to that of diamond. Recent studies have shown that cBN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine) how all of the production parameters (boron and nitrogen sources, composition of the gas used, the material covered (substrate), plasma density, RF power, bias voltage, substrate temperature) affect on the properties (cBN content and mechanical stresses) and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories with some possible additions and changes. The cBN films were produced in the plasma equipment and was studied with the measurement and testing facilities that already exist in addition to measurement and testing equipment acquired within the budget of this project. The optimum production conditions of cBN with desired mechanical and optoelectronic properties were studied experimentally

Bor nitrür üretimi.

Boron nitride is found mainly in two crystal structures; in hexagonal structure (h-BN) which is very much like graphite and in cubic structure (c-BN) with properties very close to those of diamond. h-BN is a natural lubricant due to its layered structure. It is generally used in sliding parts of the moving elements such as rotating element beds in turbine shafts. Since c-BN is the hardest known material after diamond it is used in making hard metal covers. In addition to its possible microelectronics applications (can be used to make p-n junction), its resistance to high temperatures and its high forbidden energy gap are its superiorities over diamond. Recent studies have shown that c-BN can be produced by Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD) in plasma. But these studies have failed to determine how all of the production parameters (boron and nitrogen sources, composition of the gas used, substrate, RF power, bias voltage, substrate temperature) affect the c-BN content, mechanical stress and the deposition rate of the product with a systematic approach. The systematic study was realized in the range of available experimental ability of the present PVD and CVD equipment and accessories. The BN films were produced in the plasma equipment for CVD using RF and MW and magnetron sputtering and were studied with the measurement and testing facilities. It is believed that with this approach it will be possible to collect enough experimental data to optimize production conditions of BN with desired mechanical and optoelectronic properties. h-BN films were successfully deposited in both systems. It was possible to deposit c-BN films with the MW power, however they were weak in cubic content. Deposition at low pressures eliminated the hydrogen contamination of the films. High substrate temperatures led to more chemically and mechanically stable films.M.S. - Master of Scienc

İnce film fotovoltaik aygıt üretiminde kullanılan plazma destekli kimyasal buhar biriktirme (PECVD) süreçleri ve ekipmanının modelleme ve optimizasyonu.

Plasma enhanced chemical vapor deposition (PECVD) is a common technique used in thin film based device fabrication. Operation conditions of a PECVD reactor need to be optimized in terms of deposition conditions as well as plasma cleaning procedures to deliver desired deposited material qualities. In addition, interactions with external support systems such as gas lines and cabinet, compressors and utility production units need to be understood and characterized. Modeling, whether based on fundamental principles or experimental data, is an essential tool in this optimization process, reducing the time required for experimentation. In this work, a first principles based thermal model of the system is constructed, guiding the design of an improved PECVD chamber delivering better substrate temperature levels and uniformity. On the other hand, material optimization work is supported by the identification of empirical models based on designed experiments, since fundamental models for these interactions are too complicated to be modeled accurately. Individual thin film layers, involved in thin film photovoltaic devices, were optimized in terms of crystallinity, thickness, deposition rate as well as critical optical and electrical properties. The growth of hydrogenated silicon thin films in amorphous (a-Si:H), nano-crystalline, and micro-crystalline regions with intrinsic, nand p- doping types were characterized and optimized. Amorphous silicon nitride (SiNx) thin films with tunable silicon and nitrogen concentration, silver thin films with controlled thickness profile down to nm scale, aluminum doped zinc oxide (AZO) thin films with repeatable uniform conductivity were realized successfully. After completing the optimization of these individual layers, several thin film silicon based photovoltaic devices were fabricated. The different performances that are reported in this work include a p-i-n structured homojunction a-Si:H device, a heterojunction device and a heterojunction with intrinsic thin layer (HIT) structured device. The efficiency values of 2.9 % (initial) for a-Si:H p-i-n structure, 15.9 % for heterojunction solar device and 12.5 % for one sided HIT device were recorded.Ph.D. - Doctoral Progra

High Haze Nano Textured Aluminum doped Zinc Oxide withPlasmonic Silver Nanoparticles for Enhanced Optical Absorption and Photocurrent of a Si H thin film

We report on fabrication of plasmonic interfaces consisting of Ag nanoparticles on flat and textured Al:ZnO for use at the front surface of thin film solar cells to enhance light trapping and photo-conversion efficiencies. We show that outstandingly high transmittance haze is achieved from single step HCl surface textured Al:ZnO and demonstrate Ag dewetting on textured and flat Al:ZnO surfaces upon annealing at moderate temperatures. Optical response of these plasmonic interfaces clearly display plasmonic resonances in the visible and near infrared, which is crucial for enhancement of photovoltaic conversion efficiency in thin film solar cells

Effects of glass substrate coated by different-content buffer layer on the quality of poly-Si thin films

WOS: 000389199800009In 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 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, WeinheimTUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [112T084]; Duzce UniversityDuzce University [2016.05.02.412]This work was funded by TUBITAK under the project number 112T084 and Scientific Research Project Fund of Duzce University under the project number 2016.05.02.412. The authors would like to thank Sedat Canli for his valuable contributions

Enhanced Optical Absorption and Spectral Photocurrent in a-Si:H by Single- and Double-Layer Silver Plasmonic Interfaces

Single and double plasmonic interfaces consisting of silver nanoparticles embedded in media with different dielectric constants including SiO2, SiNx, and Al:ZnO have been fabricated by a self-assembled dewetting technique and integrated to amorphous silicon films. Single plasmonic interfaces exhibit plasmonic resonances whose frequency is red-shifted with increasing particle size and with the thickness of a dielectric spacer layer. Double plasmonic interfaces consisting of two different particle sizes exhibit resonances consisting of double minima in the transmittance spectra. The optical extinction of a-Si:H deposited on these interfaces is broadened into the red indicating higher absorption and/or scattering at wavelengths higher than those typically absorbed by a-Si:H without plasmonic interfaces. While the photocurrent shows an overall decrease for the samples with the interfaces, significant enhancement of photocurrent is observed near the low-energy edge of the bandgap (600-700 nm). These results correlate well with the broadened extinction spectra of the interfaces and are interpreted in terms of enhanced absorption in that region

Efektivní pasivace povrchu černého křemíku vrstvou hydrogenizovaného amorfního křemíku naneseného pomocí plazmou podpořené depozice z plynné fáze.

Solární články na bázi černého křemíku (b-Si) se ukázaly ve fotovoltaice (PV) jako nadějné a přesahující 22% účinnost. Pro dosažení vysoké účinnosti u povrchů b-Si je nejdůležitějším krokem efektivní pasivace povrchu. Dosud je nejúčinnější doba životnosti minoritních nosičů dosahována depozicí několik atomů tenké vrstvy Al2O3 nebo tepelného SiO2. Plazmou podpořená chemická depozice z par (PECVD) vrstvy hydrogenizovaného amorfního křemíku (a-Si: H) jako pasivace b-Si je jen zřídka hlášena kvůli problémům s konformitou. V této současné studii jsou b-Si povrchy superponované na standardní pyramidální textury, také známé jako modulované povrchové textury (MST), úspěšně pasivovány konformními vrstvami a-Si:H nanesenými PECVD. Je ukázáno, že za správných podmínek plazmou podpořené depozice mohou efektivní doby životnosti minoritních nosičů vzorků vybavených přední MST a zadní standardní pyramidální strukturou dosáhnout až 2,3 ms. Cesta ke konformnímu růstu je popsána a vyvinuta za pomoci transmisních elektronových mikroskopických (TEM) obrazů. Pasivované vzorky MST vykazují méně než 4% odraz v širokém spektrálním rozsahu od 430 do 1020 nm.Solar cells based on black silicon (b-Si) are proven to be promising in photovoltaics (PVs) by exceeding 22%efficiency. To reach high efficiencies with b-Si surfaces, the most crucial step is the effective surface passivation. Up to now, the highest effective minority carrier lifetimes are achieved with atomic layer-deposited Al2O3 or thermal SiO2. Plasmaenhanced chemical vapor deposition (PECVD)-grown hydrogenated amorphous silicon (a-Si:H) passivation of b-Si is seldom reported due to conformality problems. In this current study, b-Si surfaces superposed on standard pyramidal textures, also known as modulated surface textures (MSTs), are successfully passivated by PECVD-grown conformal layers of a-Si:H. It is shown that under proper plasma-processing conditions, the effective minority carrier lifetimes of samples endowed with front MST and rear standard pyramidal textures can reach up to 2.3 ms. A route to the conformal growth is described and developed by transmission electron microscopic (TEM) images. Passivated MST samples exhibit less than 4% reflection in a wide spectral range from 430 to 1020 nm