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Progress is reported on the following: theoretical modeling, deposition and doping studies, experimental methods for the characterization of a-Si:H, formation of solar-cell structures, theoretical and experimental evaluation of solar-cell parameters, and stability studies. (MHR)

The protein-sparing and ketogenic effect of postoperative infusion of maintenance solutions containing either 3.5% amino acids or 5% dextrose in 0.33 normal (N) saline was compared by nitrogen balance and urinary acetone determination in 31 patients. A specific muscle protein sparing effect was determined by quantitation of excretion of 3-methylhistidine in seven patients of the amino acid group and eight patients in the dextrose group. In addition, an extensive hormone and substrate profile was determined. It was found that amino acid infusions not only produce a less negative nitrogen balance but also significantly reduce excretion of 3-methylhistidine indicating specific preservation of the muscle compartment.

Amorphous silicon (a-Si) solar cells have been fabricated in SiH 4 glow discharges containing various impurity gases such as N 2 , H 2 O, CH 4 , etc. The effect of these impurity gases on the photovoltaic properties are discussed. Experimental data are also presented for the variation of photovoltaic properties with deposition temperature, annealing temperature in air, and temperature during operation.

A series of amorphous silicon films were grown under identical conditions in a dc glow discharge with different impurity gases added to the silane discharge atmosphere. The constant surface photovoltage technique was used to measure both the diffusion length and the space‐charge width as a function of the time exposed to 1 sun illumination. In most cases large changes were observed in the first 48 hours of light soaking with much smaller changes observed in the next 452 hours. After 500 hours of light soaking, diffusion lengths >0.24μm were observed only in films made with pure silane or with impurities such as CH4, SiH2Cl2, or SiF4 present. Films made in the presence of impurity gases such as N2, C2H4, or (SiH2)2O exhibited diffusion lengths

This research program consisted of five tasks. Task 1, Amorphous Silicon Materials Research, involved producing and optimizing amorphous silicon material. Task 2, Non-Semiconductor Materials Research, involved producing nonsemiconductor materials required to make high-performance, amorphous silicon solar cells. Task 3, Solar Cell Research, involved fabricating and characterizing high-efficiency, single-junction, p-i-n amorphous silicon solar cells. In Task 4, Monolithic, Intra-Connected Cells/Submodule Research, research and development was performed to produce submodules of monolithic, intraconnected solar cells. In Task 5, Multi-Chamber Deposition System, a multi-chamber system was designed to fabricate submodules of at least 1000 cm/sup 2/. The major goals of the program are: (1) to obtain a conversion efficiency of at least 12% (AM1) in a single-junction, p-i-n, 1-cm/sup 2/ solar cell; (2) to eliminate the deleterious effects of light-induced, metastable centers; (3) to operate a multi-chamber deposition a-Si growth system; and (4) to demonstrate a stable submodule with an 8% conversion efficiency (AM1) and a total area of at least 1000 cm/sup 2/.

The Solarex Thin Film Division started commercial production of amorphous silicon solar cells for consumer applications in February 1984. Since that time, Solarex has produced more than twenty different types of amorphous silicon solar modules with sizes varying from 0.5cm2 to 1000cm2. The modules contain from 2 to 30 cells connected in series by sequentially patterning the various layers in the solar-cell structure. Conversion efficiencies as high as 10.9% have been obtained with superlattice p layers in 1.16cm2 p-i-n and efficiencies up to 8.7% have been obtained in large area modules (active area = 864cm2).

This report present results of the third phase of research in high-efficiency, single-junction, monolithic, thin-film, a-Si solar cells. Six glow-discharge deposition systems, including an in-line multichamber system, were used to grow both doped and undoped a-Si films. In single load-lock system, a-Si was deposited over 1000- cm{sup 2} substrates with less then a 1% variation in thickness and low oxygen impurity levels. The system produced 1000-cm{sup 2} submodules with active-area efficiencies of 8.7%. A model was developed for light scattering in textured tin oxide that predicts scattered transmission through the air/glass/tin oxide/air configuration to within a few percent. Textured tin oxide films were grown by chemical vapor deposition using tin tetrachloride. Solar-cell efficiencies of about 11% were obtained in small-area p-i-n cells with reflective back contacts of Ti/Ag that exhibit external quantum efficiencies as high as 58.7% at 700 nm; other cells with ITO/Ag back contacts have had quantum efficiencies as high as 64% at 700 nm. High-performance cells were fabricated by employing dopant and carbon concentration gradients near the p/i interface. Total-area efficiencies around 8% were obtained for submodules in which the patterning was done by laser scribing. 11 refs., 35 figs., 18 tabs.

It is suggested that the timing and magnitude of an explosive growth period in photovoltaics will be strongly influenced by factors related to the use of fossil fuels. Depletion of fossil fuels in some parts of the world is likely to cause significant changes in the energy policies of various governments and to result in higher energy costs to the consumer. Perhaps even more significant is the fact that the growing consumption of fossil fuels is contaminating the global environment at an increasing rate, and this contamination may lead to drastic changes in climate. It is emphasized that photovoltaics represents one of the few clean energy options for a pollution-free future. >

Measurements of both primary and secondary photocurrents for photon energies between 0.58 and 2.0 eV in a-Si:H solar-cell structures have been used to provide information about the density of states above the valence band as well as show that holes are mobile deep in the bandgap. The drift mobility is independent of excitation energy, indicating that the majority carriers are excited to the same states, irrespective of the excitation energy. Deposition studies in the dc proximity system have shown that the conductivity and photoconductivity of doped films (both boron- and phosphorus-doped) increase with substrate temperature. Mass spectroscopy studies have shown that the larger Si/sub x/H/sub y//sup +/ clusters are favored by operating rf discharges at low rf powers and high pressures. The Hall mobility is roughly constant below 360 K but exhibits a thermal activation energy of approx. 0.13 eV at higher temperatures. These observations rule out simple extended-state transport as the conduction mechanism. The photoelectromagnetic effect has been used to estimate the hole lifetime (approx. 3.4 x 10/sup -7/s) in undoped a-Si:H; the electron lifetime is approx. 1.7 x 10/sup -6/s. An a-Si:H monolithic solar panel consisting of 16 cells in series has been fabricated on a 4'' xmore » 4'' glass substrate (63 cm/sup 2/ of active area), and the panel exhibits a conversion efficiency of 3.6%. In another series of experiments, the thicknesses and doping levels of p-i-n cells made in a dc(P) discharge were optimized. The best cell made in these experiments had an efficiency of 5.3% with an area of 1.19 cm/sup 2/.« less

This report describes the work performed at RCA Laboratories on the five research tasks of the present contract. The section on theoretical modeling deals with the Meyer-Neldel rule and the thermal generation of Frenkel defects in a-Si:H. In Section III, Deposition and Doping Studies, we describe our deposition systems and doping studies involving fluorine, carbon, and nitrogen. The next section involves experimental methods for characterizing a-Si:H, and we discuss recent transport measurements in p-type a-Si:H, conductivity measurements as a function of dehydrogenation, tunneling in a-Si:H, surface studies of Pt deposition, and Schottky barriers between electrolytes and a-Si:H (values of V/sub oc/ as high as 1.5 V have been obtained with these barriers). In Section V, Formation of Solar-Cell Structures, we present optimization data for front and back cermet contacts, and we show experimental data for an MIPS structure (MIS cell with a thin p+ layer) as well as for a graded p-i-n cell. Section VI involves the theoretical and experimental evaluation of solar-cell parameters. Laser scanning has been used to investigate the damage created by electron-beam evaporation and to determine the various contributions to the series resistance. Collection efficiency measurements have been performed as a function of bias and indicatemore » that an internal field is necessary for efficient collection. We also discuss the junction characteristics of Pt diodes in terms of a Mott barrier.Finally, we present results on the degradation of a-Si:H cells during fabrication and upon exposure to humidity.« less

We describe a modified Triode Optical Gate (TOG) liquid crystal device that exhibits a very effective electrically driven erase or turn-off operation. The modified device retains the gating, modulation, and enhancement characteristics of the original. These operations, along with the new erase mode, depend on rotation of the direction of the electric field applied to the liquid crystal by a three terminal electrode structure. The paper will also present an analyses of TOG operation in terms of the spacial distribution of the fields, and give experimental results on a one-dimensional array of devices operating in a time-scanned mode.

We have studied mechanisms of back-contact formation in screen-printed Si solar cells by a fire-through process. An optimum firing temperature profile leads to the formation of a P-Si/P+- Si/ Si-Al eutectic/agglomerated Al at the back contact of a Si solar cell. Variations in the interface properties were found to arise from Al-Si melt instabilities. Experiments were performed to study melt formation. We show that this process is strongly controlled by diffusion of Si into Al. During the ramp-up, a melt is initiated at the Si-Al interface, which subsequently expands into Al and Si. During the ramp-down, the melt freezes, which causes the doped region to grow epitaxially on Si, followed by solidification of the Si-Al eutectic. Any agglomerated (or sintered) Al particles are dispersed with Si. Implications on the performance of the cell are described.

Resonance absorption of the 32.2 keV γ ray of 201 Hg has been observed by comparing the γ-ray activity at 300°K and 77°K. Calculations of the resonance absorption cross section favor a spin of −1 2 for the 32.2 keV level.

It is shown that the recoilless emission of low-energy internal conversion electrons, Auger electrons, and β-particles could be detected as temperature dependent effects in spectra obtained with high resolution β-spectrometers.