AmberWave (United States)

An 18 μm thin crystalline silicon solar cell was demonstrated, and its best open circuit voltage is 642.3 mV. However, this value is far from the cell’s theoretical upper limit in an ideal case. This paper explores the open circuit voltage losses of the thin silicon solar cell, starting from the ideal case, through first principle calculation and experiments. The open circuit voltage losses come from the introduced recombination due to the non-ideal surface passivation and contacts integration on front and rear surfaces, and edge isolation. This paper presents a roadmap of the open circuit voltage reduction from an ideal case of 767.0 mV to the best measured value of 642.3 mV.

A graded buffer layer is needed in order to grow III–V/SiGe on silicon substrate because of the lattice mismatch. In this work, optical absorption in the graded buffer layer is quantified by measuring the transmittances. We demonstrate a 7 µm graded buffer layer with Ge composition from 0% to 82% is equivalent to a 2 µm SiGe film with 82% Ge composition in terms of optical absorption. A SiGe solar cell was fabricated and characterized. Quantum efficiency measurements show that around 1 mA/cm2 short circuit current is generated from the graded buffer layer in the fabricated solar cell.

This work discusses Hall effect measurements by the van der Pauw (vdP) method of thin gallium arsenide phosphide (GaAs .84 P .16 ) grown on silicon (Si) substrates with graded silicon germanium (Si y Ge 1−y ) working as a buffer layer. The material characterized is used as the top cell of a recently demonstrated III–V/SiGe on Si tandem cell. We report for the first time data of the Hall mobility of the material obtained through measurement of samples with different doping levels and thicknesses and at various temperatures. This data is then used for predicting device performance using a 1-D diode model. The technique can be applied as a material screening test to ensure optimal device performance.

As every surgical procedure extraction of third molars can result in several complications, among them the mandibular angle fracture. Predisposing factors for fracture should be analyzed during and after the surgery. This paper aims to discuss the predisposing factors to the occurrence of mandibular angle fractures during and after the procedure for third molars extraction, as well as surgical principles to avoid this complication.

The value of a high performance thin silicon solar cell is based on high open circuit voltage (Voc) which is highly dependent upon surface and interface recombination. A microelectronic approach with the series and parallel fabrication of different device structures is presented. This approach includes the fabrication of planar solar cells based on different solar cell designs that maximize Voc. Subsequently, using the same solar cell design, more advanced epitaxial growth test structures were fabricated on the same substrate to understand recombination losses and Voc. In high performance thin silicon solar cells, Voc is highly sensitive to surface recombination. Achieving a good surface and interface passivation in epitaxial silicon solar cells is a challenge, especially for the absorber back surface. In this work, we used test structures embedded in the solar cells to independently optimize Voc and the back surface of a thin epitaxial absorber as well as other silicon interfaces. Most epitaxial thin silicon solar cells are fabricated with in-situ processes that lead to difficulties in the independent optimization of such surfaces. To contribute to the design space in thin silicon solar cells, we tested basic device designs and test structures that lead to high Voc. The design of basic structures is important to measure parameters that limit voltage. This is a diagnostic tool for the fabrication of high performance thin silicon solar cells. This work reports device results that exhibit a path to high open circuit voltage, determined by device design, interface recombination, and bulk lifetime. With independent optimization of parameters that limit Voc and therefore performance, this work contributes to the understanding of thin silicon solar cells.

High Ge concentration Si:Ge solar cell based on low cost Si substrate fabricated by RTCVD can be applied in multi-junction solar cell system to absorb infrared light. First principle design shows that ideally Si:Ge solar cell with 90% Ge concentration can contribute 6.2% efficiency with 16.6mA/cm 2 J sc , 472mV V oc and 79.5% FF to a multi-junction solar cell system with a 300um silicon solar cell on its top under one sun. Under 50X suns, for the same multi-junction solar cell system, efficiency of bottom Si:Ge solar cell can reach to 7.8% with 574mV V oc , 82.2% FF. Modeling results show that for 90% Ge concentration Si:Ge solar cell, if optical thickness which is 8 times of its physical thickness can be achieved, J sc can be 11.3mA/cm 2 , V oc of 462mV,and FF of 79.2%. In this case, under 50X sun efficiency an reach to 5.2% with 565mV V oc and 81.9% FF. Our initial Si:Ge solar cell without light trapping experimental results for 90%Ge with 5um absorber shows a J sc of 5.76mA/cm 2 with Si filter on top under one sun. For the same cell, V oc reaches to 205mV under 33X suns.

Thin silicon (Si) solar cells have the potential of having high performance due to lower bulk recombination which leads to high open circuit voltage [1]. It has been reported that the potential advantages of n type Si include longer lifetime, easier surface passivation, and no light-induced performance degradation [2]. Therefore, a thin Si solar cell structure based on n type absorber is an important area to investigate for higher performance. Thin Si solar cells based on epitaxial lateral overgrowth (ELO) of the n type absorber have been previously reported [3]. Open circuit voltage (Voc) is expected to be improved from utilizing an ELO solar cell due to reduced p-n junction area, which leads to a decrease in the dark saturation current. In this work, planar thin Si solar cells based upon n type epitaxial absorber have been fabricated and initial solar cell results have been analyzed. The processing steps developed for the planar solar cells will be transferred to the ELO solar cells. For the ELO solar cells, a more informative set of patterns have been designed, including different light generation area (A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</inf> ) to p-n junction area (A <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> ) ratios, different line orientations and different test patterns. PC1D software has been used to investigate the Voc and efficiency as a function of n type and p type Si absorber thickness, respectively.

High-k/Ge interfaces are significantly improved through a new interface engineering scheme of using both effective pre-gate surface GeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> passivation and post gate dielectric (post-gate) treatment incorporating fluorine (F) into high-k/Ge gate stack. Minimum density of interface states (D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> ) of 2 times 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> is obtained for Ge MOS capacitors. Hole mobility up to 396 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs is achieved for Ge pMOSFETs with EOT ~10 Aring and gate leakage current density less than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> plusmn 1 V. Best drain current to date of 37.8 muA/mum at V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> -V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> = Vd= -1.2V is presented for an L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> of 10 mum. Variable rise and fall time charge pumping (CP) method is used to investigate Ge interface property and a significant D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> reduction in both upper and lower half of bandgap is observed with F incorporation.