Crystalline silicon solar cells translate energy from the sun into electrical energy via the photoelectric effect. This technology has the potential to simultaneously reduce carbon emissions and our dependence on fossil fuels. The cost of photovoltaic energy, however, is still higher than the cost of electricity off of the grid which hampers this technologies adoption. Raising solar cell efficiency without significantly raising the cost is crucial to lowering the cost of photovoltaic produced energy. One technology which holds promise to increase solar cell efficiency is a selective emitter solar cell. In this work the benefit of selective emitter solar cells is quantified through numerical modeling. Further, the use of ultraviolet laser to create a laser doped selective emitter solar cell is explored. Through optimization of the laser doping process to minimize laser induced defects it is shown that this process can increase solar cell efficiency to over 19.1%. Additionally, 2D and 3D numerical modeling are performed to determine the limitations screen printed interdigitated back contact solar cells and the practical efficiency limit for crystalline Si solar cells.

Crystalline silicon (Si) wafers used as substrates in the semiconductor and photovoltaic (PV) industries are traditionally manufactured using a multi-wire slurry sawing (MWSS) technique. Due to its high productivity potential, the fixed abrasive diamond wire sawing (DWS) technique is of considerable interest to Si wafer producers. Although both sawing techniques are currently used in the industry, a fundamental understanding of the underlying process is still lacking, particularly for diamond wire sawing. Consequently, optimization of the wire sawing process is carried out largely based on experience and trial and error. This thesis aims to develop a systematic fundamental understanding of diamond wire sawing of Si materials used for PV applications. First of all, a comparative analysis of the characteristics of silicon wafers cut by slurry and fixed abrasive diamond wire sawing is presented. The analysis results indicate that fixed abrasive diamond wire sawing may be a viable alternative to slurry wire sawing. Modeling and experimental studies of single grit diamond scribing of Si are proposed to shed light on the basic cutting mechanisms. Although Si is brittle at room temperature, it is possible to properly control the cutting conditions to obtain a completely ductile mode of material removal. The effects of material anisotropy, abrasive grit shape, friction condition and external hydrostatic pressure on the ductile-to-brittle mode transition in cutting of single crystal Si (sc-Si) are systematically investigated. Multicrystalline Si (mc-Si) based solar cells take up the majority of the global PV market. Hard inclusions (Silicon carbide and Silicon nitride) in multicrystalline Si (mc-Si) ingots may cause wire breakage and negatively impact the process, surface/subsurface morphology and mechanical properties of the resulting wafer. Their effects are experimentally studied through the single grit diamond scribing on the mc-Si sample with high density of inclusions. Finally, it is identified that there is a correlation between the high dislocation density and the increase of fracture toughness in mc-Si. The increase in fracture toughness leads to greater capability of ductile mode of cutting and higher specific scribing energy in the brittle fracture regime. Results of these fundamental investigations are expected to generate useful knowledge for optimizing the diamond wire sawing process in order to achieve high productivity and minimum surface/subsurface damage.

Thesis (Ph.D.)--University of Delaware, 2008. / Adviser: Robert Birkmire. Includes bibliographical references.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Melkote, Shreyes; Committee Member: Danyluk, Steven; Committee Member: Griffin, Paul; Committee Member: Johnson, Steven; Committee Member: Kalejs, Juris; Committee Member: Sitaraman, Suresh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

abstract: Silicon solar cells with heterojunction carrier collectors based on a-Si/c-Si heterojunction (SHJ) have a potential to overcome the limitations of the conventional diffused junction solar cells and become the next industry standard manufacturing technology of solar cells. A brand feature of SHJ technology is ultrapassivated surfaces with already demonstrated 750 mV open circuit voltages (Voc) and 24.7% efficiency on large area solar cell. Despite very good results achieved in research and development, large volume manufacturing of high efficiency SHJ cells remains a fundamental challenge. The main objectives of this work were to develop a SHJ solar cell fabrication flow using industry compatible tools and processes in a pilot production environment, study the interactions between the used fabrication steps, identify the minimum set of optimization parameters and characterization techniques needed to achieve 20% baseline efficiency, and analyze the losses of power in fabricated SHJ cells by numerical and analytical modeling. This manuscript presents a detailed description of a SHJ solar cell fabrication flow developed at ASU Solar Power Laboratory (SPL) which allows large area solar cells with >750 mV Voc. SHJ cells on 135 um thick 153 cm2 area wafers with 19.5% efficiency were fabricated. Passivation quality of (i)a-Si:H film, bulk conductivity of doped a-Si films, bulk conductivity of ITO, transmission of ITO and the thickness of all films were identified as the minimum set of optimization parameters necessary to set up a baseline high efficiency SHJ fabrication flow. The preparation of randomly textured wafers to minimize the concentration of surface impurities and to avoid epitaxial growth of a-Si films was found to be a key challenge in achieving a repeatable and uniform passivation. This work resolved this issue by using a multi-step cleaning process based on sequential oxidation in nitric/acetic acids, Piranha and RCA-b solutions. The developed process allowed state of the art surface passivation with perfect repeatability and negligible reflectance losses. Two additional studies demonstrated 750 mV local Voc on 50 micron thick SHJ solar cell and < 1 cm/s effective surface recombination velocity on n-type wafers passivated by a-Si/SiO2/SiNx stack. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

This dissertation main point is to take up with fotovoltanic cells metering methods. Dissertation work dwells with the most common defects rising during the fotovoltanic cells manufacturing. Also, there is a diagnosis workshop proposal and realisation. Workshop uses the Light Beam Inducted Voltages (LBIV) method. By the help of this method, fotovoltanic cells structures are analised and compared to the Light Beam Inducted Current (LBIC).

<p> A technology to produce low cost solar cells was transferred to a microelectronics institution. Appropriate processing equipment was obtained and modifications to the procedure were performed which would permit the manufacture of 100-200, 3 inch diameter silicon solar cells per day. </p> / Thesis / Master of Engineering (ME)

<p> Silicon solar cells were produced using inexpensive techniques for obtaining high efficiencies. Large area cells were made with efficiencies greater than 10% (AM1) which were subsequently mounted on a Solar panel for future evaluation. </p> / Thesis / Master of Engineering (MEngr)

This thesis focuses on improving the adhesion of electroless metal layers plated to pit contacts in interdigitated, backside buried contact (IBBC) solar cells. In an electrolessly plated, pit contact IBBC cell, the contact grooves are replaced with lines of pits which are interconnected by the plated metal. It is shown, however, that electroless metal layers, plated by the standard IBBC plating sequence, are not adherent on pit contact IBBC solar cells. The cause of this adhesion problem is investigated by examining the adhesive properties of each of the metal layers in the electroless metallization sequence on planar test structures. This investigation reveals that Pd activation of heavily P diffused Si impedes Ni silicide growth and that, in the absence of a silicide at the Ni/Si interface, an electrolessly plated Cu layer will cause the underlying Ni layer to peel away from the substrate. It is also found that the Ni silicidation process itself intermittently causes the unreacted Ni to spontaneously peel away from the substrate. An electroless metallization sequence that results in thick, adhesive Cu deposits on planar &lt 100&gt surfaces is developed in this thesis. It is shown that this process leads to the formation of a Ni silicide on both n- and p- type, heavily diffused surfaces. Fully plated, pit contact IBBC solar cells were not able to be fabricated during the course of this work but it is reasonable to expect that the modified plating sequence developed in this work will result in the metal layers being adhesive on these cells.

The objective of this thesis is to develop low-cost high-efficiency crystalline silicon solar cells which are at the right intersection of cost and performance to make photovoltaics (PV) affordable. The goal was addressed by improving the optical and electrical performance of silicon solar cells through process optimization, device modeling, clever cell design, fundamental understanding, and minimization of loss mechanisms. To define the right intersection of cost and performance, analytical models to assess the premium or value associated with efficiency, temperature coefficient, balance of system cost, and solar insolation were developed and detailed cost analysis was performed to quantify the impact of key system and financial parameters in the levelized cost of electricity from PV.