Angular Dependence of Solar Cell Parameters in Crystalline Silicon Solar Cells Textured with Periodic Array of Microholes

Surface texturing is an indispensable way of increasing absorption in solar cells. In order to properly characterize the effect of texturing, the angular dependence of the incidence light should be addressed. This is particularly important when the actual application where the incidence angle of the sunlight varies during the day is considered. This study presents the angular dependence of solar cell parameters in the case of periodically textured crystalline silicon (c-Si) solar cells with microholes. A standard solar cell with pyramid texturing is also studied for comparison. It is shown that the incidence angle for the highest efficiency depends on the surface structure. While a standard pyramid-textured surface performs best at the zero angle of incidence, it is needed to tilt the sample with microholes textures 15 degrees with respect to the surface normal. This is also confirmed by the simulation study performed for the structures presented in this study

The role of talent management on job satisfaction andorganizational commitment

Araştırmamın amacı Yetenek Yönetimi, İş Tatmini ve Örgütsel Bağlılığın tanımlanması yanında çalışana ve örgüte ne gibi etkiler getirdiğinin açıklanmasıdır. Yetenek Yönetimi, Örgütsel Bağlılık ve İş Tatmini, her işletmede büyük öneme sahip olan çalışan verimliliği üzerinde etkilidir. Uzun vadeli ve stratejik kavramlar olan bu yaklaşımlar, iş gücü devir oranının düşürülmesi, örgüt iklimi oluşturulması gibi farklı kavram ve maliyet unsurları üzerinde de etkilidir. Çalışanın verimli olması, örgütsel amaçlara daha hızlı ve verimli şekilde ulaşmayı sağlar. Kopyalanamayan tek unsur sayılan İnsan Kaynağı Yönetiminde etkili olan bu unsurlar saha çalışması ile netleştirilmeye çalışılmış ve çeşitli önerilerde bulunulmuştur.The purpose of my research is to describe the effects of Talent Management, Job Satisfaction and Organizational Commitment also explain the effects on the employees and the organization Talent Management, Organizational Commitment and Job Satisfaction are effective on employee productivity, which has great importance in every business. These approaches, which are long-term and strategic concepts, are also effective on different concepts and cost elements such as decrease the turnover rate and creating an organizational climate. The productivity of the employee enables to reach the organizational goals faster and more efficiently. The elements which has an effect on the human resources management that considered, as the only element cannot be copied has been tried to be clarified and various suggestions have been made

Tek kristal silisyum güneş gözeleri için lazerle desenlendirilmiş maske oksit katmanı kullanılarak tek aşamalı katkılama ile seçici emiter oluşturulması.

Selective emitter is one of the new approaches for higher efficiency solar cells. Although selective emitter cells could be processed by several different methods such as; etch back process, laser doping, ion implantation, doping paste, a different method based on diffusion through a laser patterned oxide layer was studied in this thesis. Utilization of pattern oxide layer as a diffusion barrier enables to obtain selective emitter profile via single step doping which reduces overall production cost and time significantly. In this work, selective emitter solar cells were fabricated via single step doping through a laser patterned oxide. Oxide thickness, doping recipe, laser parameters and wet cleaning steps were optimized to reach the sheet resistance values needed for an efficient cell design. In addition, surface passivation studies were also conducted to further improve cell performance. A low temperature, dry oxidation step was also added to process sequence. Then, monocrystalline-Si selective emitter and reference solar cells were fabricated. Both electrical and optical characterizations including reflection, lifetime, external quantum efficiency, Suns-Voc and current-voltage measurements were systematically carried out. It was observed that cells based on that new selective emitter structure could be used to reach higher conversion efficiency values compared to standard cell design with a proper finger designM.S. - Master of Scienc

Enhanced metal assisted etching method for high aspect ratio microstructures: Applications in silicon micropillar array solar cells

A solar cell device, fabricated on high density array cylindrical pillars, enables photogenerated carrier collection in the radial direction, thus shortening the path length of the carriers reaching the junction. It also provides advantages over conventional planar junction solar cells, such as reduced surface reflectance and enhanced light trapping. In this study, highly ordered Si micropillars were fabricated by photolithography and metal assisted etching (MAE) methods. It is shown that the use of ethanol as a solvent during the etching process and increasing HF concentration in the MAE solution both improve the quality of the surfaces of the pillars. Micropillars with smooth sidewalls and a high aspect ratio were obtained in this way. Solar cells with a radial junction were then fabricated on these micropillars. Standard doping, SiO2/SiNx passivation, and metallisation steps were carried out for the fabrication of solar cells with different micropillar lengths. A significant decrease in reflectance values was observed as the micropillar length increased, as expected. Solar cell short circuit current density (J(SC)) and efficiency (eta) of the solar cells tended to increase with micropillar length up to 11.5 mu m and then decrease due to increased surface recombination. The maximum efficiency achieved in this study is 17.26%

PASSIVATION OF SILICON SOLAR CELLS VIA LOW TEMPERATURE WET CHEMICAL OXIDATION

In the development of high efficiency crystalline Si solar cells, decreasing bulk and surface recombination velocities of the minority carriers is vital. As the bulk recombination could be suppressed by enhancing the material quality, the effect of surface recombination on cell performance becomes more dominant. Also, recent studies have revealed that the area under the metal contacted region needs to be passivated to minimize the carrier recombination. The passivation of front and back surface of the cell can be achieved using different techniques and materials. Dry oxidation is a well-known process by the industry and requires high temperature treatment that increases thermal budget of the whole fabrication sequence and also degrades bulk lifetime. For this reason, a low temperature technique like wet chemical oxidation is highly desirable for the growth of thin oxide layers. In this work, 4 different wet chemical oxidation techniques based on nitric acid (HNO3), hydrogen peroxide (H2O2), RCA II (HCl: H2O2) and hydrochloric acid (HCl) solutions were studied and corresponding cell performances was compared with that of dry oxidation

Periodic micro hole texturing with metal assisted chemical etching for solar cell applications: dependence of etch rate on orientation

Surface texturing is an indispensable process for solar cell fabrication. The interaction of the surface with the incoming sunlight is controlled by texturing in such a way that the absorption is maximized through multiple interactions. Wet and dry etching techniques have been used to create textured surfaces on solar cells. Other than standard alkaline texturing used by the industry, metal assisted etching (MAE) appears to be a promising texturing technique with greater potential application for multi-crystalline solar cell fabrication. It is possible to achieve both random and periodic patterns with MAE which is relatively cheaper than dry plasma etching techniques. In this study, periodic hole patterns with micron sized diameters and periodicity were aimed to be achieved. Etching rate was shown to be strongly dependent on the surface orientation. Uniformly distributed patterns with various diameter and period values were successfully obtained. Fabrication of solar cells on these surface patters were demonstrated. Performance of solar cells was evaluated through parameters like efficiency, open circuit voltage and short circuit curren

Enhanced Passivation Properties of a-Si:H and Reactive ITO Sputtering for SHJ Solar Cells

Enhancement of the conversion efficiency of silicon solar cells is crucial for the improvement of renewable electricity resources. The device properties such as minority carrier lifetime, series resistance, contact resistance and optical properties should be improved simultaneously to achieve higher photo conversion efficiencies. We use industry compatible processes flow to fabricate large-area silicon heterojunction (SHJ) solar cells combined with reactive ITO sputtering. The passivation properties of a-Si:H layer was improved by hydrogen plasma treatment resulting in a lower interface defect density and higher "H" content in the deposited thin a-Si:H layer. Moreover, carrier density, mobility and resistivity of ITO layer was analyzed and the best deposition condition of ITO is integrated to SHJ solar cell process sequence. Contact resistivity between ITO and low temperature silver paste was decreased by optimized drying and curing temperature parameters. In large- area SHJ solar cell, we have achieved conversion efficiency of 20.8%

Fourteen percent efficiency ultrathin silicon solar cells with improved infrared light management enabled by hole-selective transition metal oxide full-area rear passivating contacts

The present study investigates the application of hole-selective transition metal oxide (TMO) layers (MoOx, V2Ox, and WOx) with silver (Ag) as full-area rear contact to 22.5 mu m-thick low-quality Cz p-type c-Si solar cells. Thin films of metal oxides are deposited directly on p-type c-Si by thermal evaporation at room temperature. The large work function of these TMOs creates strong accumulation at the interface with p-type c-Si, which allows only holes to transport and simultaneously suppress the interfacial recombination current density (J(0)) and contact resistivity (rho(c)). The current generation and losses of 22.5 mu m-thick solar cells with different hole-selective TMO/Ag at the rear are simulated. The presence of TMO/Ag at the rear is found to significantly reduce parasitic light absorption at longer wavelengths which becomes more pronounced for ultrathin wafers, providing significant advantages over conventional Al contact. The best device performance was attained by the MoOx/p-type c-Si solar cells, demonstrating a considerably high efficiency (eta) of 14% with V-oc of 555 mV, FF of 76.0%, and J(sc) of 33.2 mA/cm(2). Furthermore, the present work is the first to employ MoOx, V2Ox, and WOx as rear contact in ultrathin p-type c-Si solar cells