Four-Junction Wafer-Bonded Concentrator Solar Cells Dimroth, Frank; Tibbits, Thomas N. D.; Niemeyer, Markus ...
IEEE journal of photovoltaics,
2016-Jan., 2016-1-00, 20160101, Volume:
6, Issue:
1
Journal Article
Peer reviewed
Open access
The highest solar cell conversion efficiencies are achieved with four-junction devices under concentrated sunlight illumination. Different cell architectures are under development, all targeting an ...ideal bandgap combination close to 1.9, 1.4, 1.0, and 0.7 eV. Wafer bonding is used in this work to combine materials with a significant lattice mismatch. Three cell architectures are presented using the same two top junctions of GaInP/GaAs but different infrared absorbers based on Germanium, GaSb, or GaInAs on InP. The modeled efficiency potential at 500 suns is in the range of 49-54% for all three devices, but the highest efficiency is expected for the InP-based cell. An efficiency of 46% at 508 suns was already measured by AIST in Japan for a GaInP/GaAs//GaInAsP/GaInAs solar cell and represents the highest independently confirmed efficiency today. Solar cells on Ge and GaSb are in the development phase at Fraunhofer ISE, and the first demonstration of functional devices is presented in this paper.
Multiple-quantum-well (MQW) top cells can enhance the performance of multi-junction solar cells since the absorption edge of top and middle subcells can be tuned with the MQWs to maximize the ...efficiency. The radiative dominance of MQW top cells can enhance photon coupling, which can potentially reduce the spectral sensitivity of the device and, thus, raise the energy harvest. We present experimental results on photon coupling in dual-junction cells with GaInP top cells containing GaInAsP quantum wells along with theoretical calculation based on a detailed balance model. It is observed that at high concentration, approximately 50% of the dark current of an MQW top cell is transferred to the photocurrent of the cell in the bottom, which is much higher than any previously reported values.
The next generation of multi-junction concentrator solar cells will have to reach higher efficiencies than today's devices. At the same time these solar cells must be reliable in the field, be ...manufacturable with good yield and at sufficiently low cost. Inevitably the request of higher efficiency requires four or even more junction devices. A four-junction solar cell combination of GaInP/GaAs//GaInAsP/GaInAs with bandgap energies of 1.9, 1.4, 1.1, 0.7 eV is developed in a close collaboration between the Fraunhofer ISE, Soitec, CEA-LETI and HZB. This 4-junction cell hits close to the optimum of theoretical efficiency contour plots and has the potential to reach efficiencies up to 50 % under concentration. Challenges are associated with lattice-mismatch between GaAs and InP which is overcome by direct wafer-bonding. The high cost of the InP is addressed by the use of engineered substrates which only require a 500 nm thin mono-crystalline InP layer instead of several hundred μm. Excellent solar cell results up to 44.7 % efficiency have been obtained under concentration for devices manufactured on InP bulk substrates. The high cell efficiency is also supported by out-door characterization of one cell below a Fresnel lens with 16 cm 2 aperture area. 38.5 % conversion efficiency has been measured for this mono-module in Freiburg under real operating conditions without any corrections.
The purpose of this review is to assess the relationship between mood disorders and development, course, and associated morbidity and mortality of selected medical illnesses, review evidence for ...treatment, and determine needs in clinical practice and research.
Data were culled from the 2002 Depression and Bipolar Support Alliance Conference proceedings and a literature review addressing prevalence, risk factors, diagnosis, and treatment. This review also considered the experience of primary and specialty care providers, policy analysts, and patient advocates. The review and recommendations reflect the expert opinion of the authors.
Reviews of epidemiology and mechanistic studies were included, as were open-label and randomized, controlled trials on treatment of depression in patients with medical comorbidities. Data on study design, population, and results were extracted for review of evidence that includes tables of prevalence and pharmacological treatment. The effect of depression and bipolar disorder on selected medical comorbidities was assessed, and recommendations for practice, research, and policy were developed.
A growing body of evidence suggests that biological mechanisms underlie a bidirectional link between mood disorders and many medical illnesses. In addition, there is evidence to suggest that mood disorders affect the course of medical illnesses. Further prospective studies are warranted.
High efficiency quantum well GaAs solar cells have been successfully applied in commercial multijunction concentrator cells to increase the absorption in the infrared and provide variability of the ...absorption edge to optimise energy harvesting. Multiple quantum well (MQW) top cells can further improve the performance of multijunction solar cells since the absorption edge of top and middle subcells can be tuned with the MQWs to maximize the efficiency. Also, our simulations show that photon coupling resulting from the radiative dominance of the MQW top cell can make the multijunction cell less sensitive to variations in the incoming spectrum, thus further improving energy harvesting. New results on the characterisation of a novel MQW top cell will be presented along with electro- and photo-luminescence studies relevant to the photonic coupling.
GaAs based strain-balanced quantum well solar cells (SB-QWSCs) have been shown to enhance efficiency compared to a bulk control cell, if the overall photocurrent increase is not offset by the ...reduction in open-circuit voltage. Here we demonstrate the performance of QWSC in light fluxes of up to 400 suns equivalent. The QWSC maintains additivity (the total current is the sum of dark current and the photocurrent) at these concentration levels and we demonstrate an efficiency of 27.0% at 328 suns for a SB-QWSC under the low aerosol optical density spectrum (AOD). The SB-QWSC is a p-i-n structure with 50 In 0.1 Ga 0.9 As wells in the i-region and a 20 period staircase distributed Bragg reflector (DBR) optimized to reflect light in the stop-band range of (880-930) nm. The entire device is grown monolithically in a robot-loading 7times2 Thomas Swan Shower-Head Reactor recently commissioned at the University of Sheffield
Summary form only given. The highest solar cell conversion efficiencies are achieved with Four-junction devices under concentrated sunlight illumination. Different cell architectures are under ...development, all targeting an ideal bandgap combination close to 1.9 eV, 1.4 eV, 1.0 eV and 0.7 eV. Wafer bonding is used in this work to combine materials with a significant lattice-mismatch. Three cell architectures are presented using the same two top junctions of GaInP/GaAs but different infrared absorbers based on Germanium, GaSb or GaInAs on InP. The modelled efficiency potential at 500 suns is in the range of 49-54 % for all three devices but the highest efficiency is expected for the InP-based cell. An efficiency of 46 % at 508-suns was already measured by AIST in Japan for a GaInP/GaAs//GaInAsP/GaInAs solar cell and represents the highest independently confirmed efficiency today. Solar cells on Ge and GaSb are in the development phase at Fraunhofer ISE and first demonstration of functional devices is presented in this paper.
The development of appropriate AIDS risk reduction interventions targeted at African-American gay men could be aided by an awareness of their terminology for specific sexual behaviors and types of ...sexual encounters. This paper explores similarities and differences between the HIV-related sexual language of Black and White gay men. While much of the vernacular is shared, differences in some terms and greater or lesser emphasis on others are apparent.
Study of the effects of various diseases and therapeutic manipulation of pulmonary vascular resistance on the right ventricle has been restricted by methodologic limitations. The radioactive gas in ...solution, krypton-81m was used to study the right ventricle and the technique was compared with a technetium-99m method. In 22 subjects, first-pass krypton-81m right ventricular ejection fraction, acquired both in list mode and electrocardiogram-gated frame mode, correlated well (r = 0.81 and 0.86, respectively, p less than 0.01) with that determined by technetium-99m first-pass studies over a broad range of ventricular function. The reproducibility of the technique was excellent (r = 0.84 and 0.95 for each acquisition mode, respectively). Krypton-81m first-pass studies provide accurate and reproducible estimates of right ventricular function. Use of krypton allows multiple measurements, with or without perturbations, over a short period of time.
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