Abstract: The apparatus includes a card which entitles the holder to a number of units of parking time represented by discrete capacitances carried by the card. The parking time is metered by a card reader which accepts the card senses the capacitance carried thereby and measures out a unit of parking time for each unused capacitance. The reader responds to a predetermined capacitance and renders inoperative each capacitance as it is used up. The elements of each capacitance are formed so that the value of the capacitance can be greatly reduced by a mechanical or other type of punching operation. Two types of reader are disclosed, one which accepts the card in increments corresponding to a single capacitance and the other which accepts the entire card and automatically scans the capacitances carried thereby. Several forms of cards are disclosed.

Abstract: A card-operated parking system utilizes cards having a succession of discrete filtered light transmitting areas thereon. The cards operate a card reader which includes a light source and light sensing means, between which the card is inserted, and a punch which punches out a filter area after it has triggered the time-dispensing mechanism. The filters transmit light having a photon energy below a level characteristic of the filter material but absorb light having a photon energy above that level. Two light sensors are positioned in the light path, one receptive to light of the first mentioned photon energy and the other to light of the second photon energy. Only the outputs corresponding to filtered light trigger the parking time dispensing mechanism. The light source may be a tungsten filament bulb or a pair of light emitting diodes of different photon energies. The light sensing means may be a pair of photodiodes or a pair of phototransistors.

Abstract: A thin cadmium-telluride semiconductor film for use in solar cells is grown epitaxially on a second semiconductor film, typically tellurium, which may be epitaxial on a substrate semiconductor, typically single-crystal cadmium-telluride. The second semiconductor has a lower resistance to layered cleaving than the desired semiconductor. Application of a strain to the sandwich causes the desired thin CdTe layer to peel off by fracture along the plane of the second semiconductor.

Abstract: Thin semiconductor films of compounds from groups III-V of the periodic table suitable for solar cells are formed on low cost substrates by forming on the substrate an intermediate film that is chemically related to but has a lower melting point than the desired semiconductor. The desired semiconductor film is then grown on this intermediate film while it is in a molten condition. The molten intermediate layer isolates the substrate from the desired semiconductor layer so that as that layer grows, large area crystals result. The intermediate film may be a semiconductor III-V compound or may be a group III metal alloy.

Abstract: A high output solar cell comprises a three-layer semiconductor compound article, the layers being doped in pn.sub.1 n.sub.2 order in the direction of light travel, the pn.sub.1 junction being a homojunction and the n.sub.1 n.sub.2 junction being a heterojunction. The doping of the layers is such that "valley-tranferred" or "hot" electrons, so-called, are created in th p and n region secondary electron conduction bands and are transferred to the normal conduction band edge of the n.sub.2 heterojunction material and ultimately to an ohmic contact.

Abstract: Composite solar cells of improved efficiency comprise two cells of different characteristics arranged in optical series but electrically insulated from each other. Preferably, each cell is of larger crystal grain size than its substrate, which grain size is achieved by growing the cell semi-conductor on a molten intermediate rheotaxy layer of a suitable semi-conductor which solidifies at a temperature below the melting temperature of the solar cell semi-conductor. The substrate and the intermediate rheotaxy layer of the overlying cell are transparent to that fraction of sunlight which is utilized by the underlying cell. Various configurations of overlying and underlying cells are disclosed.

Abstract: The invention relates to a method for producing a desired thin semiconductor film for use in solar cells. The desired semiconductor is grown epitaxially on a second semiconductor film which may be epitaxial on a third semiconductor. The second semiconductor has a lower melting point than the desired semiconductor. The temperature of the second semiconductor is increased. This creates a molten state in the second semiconductor and the desired semiconductor is stripped away from the second semiconductor. The desired film may be detached by dissolving the second semiconductor with a chemical agent that dissolves the second semiconductor.