GaAsP on GaP top solar cells

GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency

A three solar cell system based on a self-supporting, transparent AlGaAs top solar cell

Development of a three solar cell stack can lead to practical efficiencies greater than 30 percent (1x,AM0). A theoretical efficiency limitation of 43.7 percent at AM0 and one sun is predicted by this model. Including expected losses, a practical system efficiency of 36.8 percent is anticipated. These calculations are based on a 1.93eV/1.43eV/0.89eV energy band gap combination. AlGaAs/GaAs/GaInAsP materials can be used with a six-terminal wiring configuration. The key issues for multijunction solar cells are the top and middle solar cell performance and the sub-bandgap transparency. AstroPower has developed a technique to fabricate AlGaAs solar cells on rugged, self-supporting, transparent AlGaAs substrates. Top solar cell efficiencies greater than 11 percent AM0 have been achieved. State-of-the-art GaAs or InP devices will be used for the middle solar cell. GaInAsP will be used to fabricate the bottom solar cell. This material is lattice-matched to InP and offers a wide range of bandgaps for optimization of the three solar cell stack. Liquid phase epitaxy is being used to grow the quaternary material. Initial solar cells have shown open-circuit voltages of 462 mV for a bandgap of 0.92eV. Design rules for the multijunction three solar cell stack are discussed. The progress in the development of the self-supporting AlGaAs top solar cell and the GaInAsP bottom solar cell is presented

Development of N/P AlGaAs free-standing top solar cells for tandem applications

The combination of a free standing AlGaAs top solar cell and an existing bottom solar cell is the highest performance, lowest risk approach to implementing the tandem cell concept. The solar cell consists of an AlGaAs substrate layer, an AlGaAs base layer, an AlGaAs emitter, and an ultra-thin AlGaAs window layer. The window layer is compositionally graded which minimizes reflection at the window layer/emitter interface and creates a built-in electric field to improve quantum response in the blue region of the spectrum. Liquid phase epitaxy (LPE) is the only viable method to produce this free standing top solar cell. Small (0.125 sq cm), transparent p/n AlGaAs top solar cells were demonstrated with optimum bandgap for combination with a silicon bottom solar cell. The efficiency of an AlGaAs/Si stack using the free standing AlGaAs device upon an existing silicon bottom solar cell is 24 pct. (1X, Air Mass Zero (AM0). The n/p AlGaAs top solar cell is being developed in order to facilitate the wiring configuration. The two terminal tandem stack will retain fit, form, and function of existing silicon solar cells. Progress in the development of large area (8 and 16 sq cm), free standing AlGaAs top solar cells is discussed

Mechanically-stacked tandem solar cells with GaAsP on GaP and silicon

Preliminary results are encouraging for the achievement of high conversion efficiencies using a GaAsP top solar cell mechanically stacked on a conventional silicon solar cell. A realistic maximum of 29.4 percent is suggested when both the top and bottom solar cells are state of the art. Practical system efficiencies greater than 25 percent are attainable in the near future with the use of a state of the art bottom solar cell

Effects of the Wisconsin Reading Design Comprehension Program on Reading Achievement and Self-Concept of Sixth Grade Students

Problem. The teaching of reading in elementary schools of America has long been a subject of intense interest to the American public. The comprehension component of the criterion referenced reading program, Wisconsin Design for Reading Skills Development, is a product being developed to teach reading skills. The main purpose of the study was to determine and describe the effects of the program on reading achievement and self-concept of sixth grade students. Method. This was a quasi-experimental study using a parametric technique. One-way multi-variate analysis of covariance and two-way univariate analysis of covariance were used to analyze the results of the Stanford Achievement test scores. Univariate analysis of covariance was used to analyze the results of the Coopersmith Self-Esteem Inventory and Michigan Educational Assessment Program. Significance of difference between independent proportions was used to analyze the WDRSD scores for the treatment group. There were forty-four sixth grade students in the treatment group (nineteen boys and twenty-five girls) and one hundred three in the control group (forty-seven boys and fifty-six girls) who were tested for treatment and sex. Results. Treatment girls scored significantly higher than non-treatment girls in reading--especially spelling. Treatment boys scored significantly higher in spelling. Both treatment boys and treatment girls met the criterion for WDRSD results. There were no significant differences between any groups on self-esteem. Conclusions. Although the comprehension component of Wisconsin Design still needs some refinement, it is a useful program worthy of further development and application

Early Days of the Maine State Prison at Thomaston

An academic history of the design and construction of the first Maine State Prison built at Thomaston, Maine. The prison, designed by and constructed under the supervision of Dr. Daniel Rose, was unique in America. The 50 solitary confinement cells were actually underground pits. Rose, as the first prison warden, employed the Auburn prison system of strictly enforced silence, hard labor, and corporal punishment intended to inspire grief and penitence. Negley K. Teeters (1896-1971)was a Professor of Criminology at Temple University, Philadelphia and a leading academic in the field of prison reform.https://digitalcommons.library.umaine.edu/mainebicentennial/1121/thumbnail.jp