Zn/sub 3/P/sub 2/ as an improved semiconductor for photovoltaic solar cells. Twelfth quarterly report, June 1, 1981-August 31, 1981

Technical Report · Sun Nov 01 04:00:00 EST 1981

OSTI ID:5690454

Al/Zn/sub 3/P/sub 2/ Schottky solar cells were prepared by depositing a thin film of Al on polycrystalline Zn/sub 3/P/sub 2/ wafers by dc sputtering. The cells had J/sub sc/ of 8 to 10 mA/cm/sup 2/ and V/sub oc/ of 0.11 to 0.24 volts. The samples were heated in air at 100/sup 0/C for several hours. The change in spectral response of the cells and Auger depth profiles indicate that Al diffuses in Zn/sub 3/P/sub 2/. The V/sub oc/ and barrier height in these cells decreased after heating. Attempts were made to find an n-type dopant for Zn/sub 3/P/sub 2/. Zn/sub 3/P/sub 2/ wafers were annealed in the presence of In, Al, Ca, As and Na, and the conductivity type remained unchanged. The effect of heat treatment on Mg/Zn/sub 3/P/sub 2/ cells prepared on thin polycrystalline Zn/sub 3/P/sub 2/ films were studied. An n/p junction was formed after heating as evidenced from the change in the cell parameters (V/sub oc/, J/sub 0/) and the spectral response. The junction depth did not follow the time dependence after prolonged heating. It is suspected that a p/sup +/ layer exists near the back contact due to diffusion of Fe in the Zn/sub 3/P/sub 2/ thin film during the film growth. The p/p/sup +/ layer gives rise to a Back Surface Field (BSF). Theoretical calculations were performed to show that the light-generated current is higher by 10 to 15% in a BSF cell if the film thickness is comparable to the diffusion length. Thin epitaxial Zn/sub 3/P/sub 2/ films were also grown on Zn/sub 3/P/sub 2/ substrates. Mg/Zn/sub 3/P/sub 2/ cells prepared on these films had total area conversion efficiencies of 2 to 3%. The barrier height of Mg/Zn/sub 3/P/sub 2/ devices were measured to be 1.1 to 1.3 eV. Low resistivity ZnSe films were obtained by co-evaporation with Al in vacuum. ZnSe/Zn/sub 3/P/sub 2/ heterojunction prepared by this method did not exhibit a photovoltaic effect. Epitaxial growth of ZnSe on Zn/sub 3/P/sub 2/ substrates was attempted by close-spaced vapor transport in Argon. ZnSe films were found to contain a significant amount of phosphorus and the devices had no photo response.

• Research Organization: Solar Energy Research Inst., Golden, CO (USA); Delaware Univ., Newark (USA). Inst. of Energy Conversion
• DOE Contract Number: AC02-77CH00178
• OSTI ID: 5690454
• Report Number(s): SERI/PR-8062-1-T13; ON: DE82004259
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
ALKALINE EARTH METALS
ALUMINIUM
CAPACITANCE
CHALCOGENIDES
CRYSTAL DOPING
CURRENTS
DIFFUSION
DIRECT ENERGY CONVERTERS
EFFICIENCY
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ELEMENTS
EPITAXY
EQUIPMENT
FABRICATION
FILMS
HEAT TREATMENTS
HETEROJUNCTIONS
IRON
JUNCTIONS
MAGNESIUM
METALS
P-N JUNCTIONS
PHOTOCURRENTS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SCHOTTKY BARRIER SOLAR CELLS
SELENIDES
SELENIUM COMPOUNDS
SEMICONDUCTOR JUNCTIONS
SOLAR CELLS
SOLAR EQUIPMENT
SPUTTERING
TRANSITION ELEMENTS
ZINC COMPOUNDS
ZINC PHOSPHIDE SOLAR CELLS
ZINC SELENIDES