Engineering topics
Publications and source records attributed to Mandelkorn, J..
Method bonds solar-cell modules between rigid or flexible base and plastic protective cover. Method relies on using one of several commercially-available, transparent, silicone adhesives as bonding agent. Should it ever be necessary to repair or replace some part of assembly, it may be possible to remove cover without destroying package since adhesive remains flexible.
The characteristics and behavior of p(+), p solar cells were investigated. The p(+), p cells were made by the removal of the n(+) surface layers from n(+), p p(+), BSF cells followed by application of a suitable contact to the resultant p(+), p structures. The open circuit voltage of p(+), p cells was found to increase with increasing 'p' bulk resistivity. The measured open circuit velocity-temperature coefficients were positive and increased with increasing resistivity. An outline of prior limitations in solar cell design is presented, and the removal of these limitations through use of BSF effects is pointed out. The study of BSF effects made feasible production of very thin high efficiency silicon cells as well as high resistivity-high efficiency cells, two desirable types of silicon cells which were previously impossible to make.
A study to determine the influence of fabrication processes and bulk material properties on the behavior of back surface field (BSF) cells is reported. It is concluded that a photovoltage is generated at the p(+), p back junction of the cell. The concept of majority carrier collection is proposed as a possible mechanism for this generation. Advantages accruing to the advent of BSF cells are outlined.
Several new types of back surface field (BSF) cells were designed and fabricated. These include boron and phosphorus diffused BSF cells, single crystal epitaxially grown BSF cells and chemically vapor deposited (CVD) polycrystalline BSF cells. Boron diffusion yielded 10 ohm-cm BSF cells with 0.6 volt open-circuit voltages and collection efficiencies equal to those previously reported for aluminum alloying. The epitaxially grown cells also exhibited high open-circuit voltages and collection efficiencies and may be more radiation damage resistant. The polycrystalline cells had very high internal series resistance. No direct relationship was found to exist between collection efficiency and open-circuit voltage in BSF cells.
The phenomenon of high-resistivity silicon solar cells manifesting high open-circuit voltages previously observed only for cells made from low-resistivity silicon is shown to be caused by the presence of a shallow diffused region at the back surface of the cell. The basic cell structure is either n+, p, p+ or p+, n, n+. The high open-circuit voltage arises from the injection and accumulation of excess majority carriers in the bulk upon illumination or application of forward bias to the structure. A working model for the cell, designated a back surface field (BSF) cell, is described, and recent developments are cited.
Several new types of back surface field (BSF) cells were designed and fabricated. These include boron and phosphorus diffused BSF cells, single crystal epitaxially grown BSF cells and chemically vapor deposited (CVD) polycrystalline BSF cells. Boron diffusion yielded 10 ohm-cm BSF cells with 0.6 volt open-circuit voltages and collection efficiencies equal to those previously reported for aluminum alloying. The epitaxially grown cells also exhibited high open-circuit voltages and collection efficiencies and may be more radiation damage resistant. The polycrystalline cells had very high internal series resistance. No direct relationship was found to exist between collection efficiency and open-circuit voltage, V sub oc in BSF cells. Results indicate that the V sub oc effect is not caused simply by the mechanism of blocking of minority carriers.
An investigation of the characteristics and behavior of 10 ohm-cm silicon cells having abnormally high open-circuit voltages was made. The cells studied were made by a new, highly simplified, contact fabrication process which creates both a contact and a thin electric field region at the cell back surface without the need for phosphorus layer removal. These cells had open-circuit voltages of about 0.58 V and their performance as a function of thickness, temperature, and 1 MeV electron irradiation is detailed. The study showed that 10 ohm-cm back-surface-field cells can have the high initial efficiencies and desirable temperature behavior of low resistivity cells. Thin back-surface-field cells were made and showed, in addition, much greater radiation damage resistance. A mechanism is proposed to explain the results.
Large decreases in short circuit current of silicon solar cells have been reported to occur as temperature is decreased below -60 C. Experimental results are presented which relate high dislocation density of the silicon bulk material of cells to the large current loss effect. These results reveal a direct relationship between low bulk dislocation density and low current loss at low temperature. Oxygen content does not appear to play a significant role in the low temperature-large current loss effect, since some Czochralski cells did not suffer from this effect whereas some float-zone cells did. Other float-zone silicon cells had only medium current losses at low temperature despite their high bulk dislocation density. It appears that use of low-dislocation-density silicon can eliminate the current loss problem in low temperature cell operation.
An investigation of the characteristics and behavior of 10 ohm-cm silicon cells having abnormally high open-circuit voltages was made. The cells studied were made by a new, highly simplified, contact fabrication process which creates both a contact and a thin electric field region at the cell back surface without the need for phosphorus layer removal. These cells had open-circuit voltages of about 0.58 V and their performance as a function of thickness, temperature, and 1 MeV electron irradiation is detailed. The study showed that 10 ohm-cm back-surface-field cells can have the high initial efficiencies and desirable temperature behavior of low resistivity cells. Thin back-surface-field cells were made and showed, in addition, much greater radiation damage resistance. A mechanism is proposed to explain the results.
Large decreases in short circuit current of silicon solar cells have been reported to occur as temperature is decreased below -60 C. Experimental results are presented which relate high dislocation density of the silicon bulk material of cells to the large current loss effect. Solar cells were made by the same processes from a variety of silicon materials, namely low-dislocation-density, high-dislocation-density float-zone, and Czochralski silicon. All cells were etched in a manner which revealed the dislocation density of the cell bulk silicon. It was found that every cell made from any of the various low-dislocation starting materials obtained from three suppliers still had a low-dislocation bulk after cell processing, and that all such cells belonged to category good. Cells made from float-zone materials showed high dislocation densities in their bulk and either fell into category poor, or had intermediate losses of short-circuit current at low temperature.
Metal pattern bonding technique for cover glass attachment to silicon solar cells for space applications
Electrode connection for n-on-p silicon solar cell
Gadolinium or samarium doped-silicon semiconductor material with resistance to radiation damage for use in solar cells
Addition of group 3 elements to silicon semiconductor material for increased resistance to radiation damage in solar cells
Doping silicon material with gadolinium to increase radiation resistance of solar cells
Li containing p-on-n and n-on-p Si cell degradation by bombardment noting carrier removal damage, annealing and radiation damage resistance
Radiation damage characteristics of lithium doped p-n solar cells and n-p solar cells
Radiation effects on boron and aluminum doped silicon solar cells and phenomenon of reverse annealing in boron-doped silicon cells