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Bube, R. H.

Publications and source records attributed to Bube, R. H..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Applied research on 2-6 compound materials for heterojunction solar cells

Several II-VI heterojunctions show promise for photovoltaic conversion of solar energy. The three of greatest interest are p-CdTe/n-CdS, p-CdTe/n-ZnSe, and p-ZnTe/n-CdSe. Several p-CdTe/n-CdS heterojunction cells have been prepared by close spaced transport deposition of p-CdTe on single crystal n-CdS, and by two source vacuum evaporation of n-CdS on single crystal p-CdTe. Both types of cells, in an experimental stage, are quite comparable, exhibiting values of quantum efficiency between 0.5 and 0.9, open circuit voltages between 0.50 and 0.66 V, fill factors between 0.4 and 0.6, and solar efficiencies up to 4 percent. Cells of p-ZnTe/n-CdSe have also been made by close spaced vapor transport deposition of n-CdSe on single crystal p-ZnTe.

Bube, R. H.↗
NASA NTRS1974

Heat treatment effects in Cu2S-CdS heterojunction photovoltaic cells

The dependence of the short-circuit current on photon energy, temperature, and the state of optical degradation (or enhancement) is determined in a study of the photovoltaic properties of Cu2S-CdS single-crystal heterojunctions. A coherent formulation is proposed for the relationship between enhancement and optical degradation and for their effects on the transport of a short-circuit photoexcited current and dark forward-bias current in a photovoltaic cell. Optical degradation in a Cu2S-CdS cell is shown to be identical to the optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal.

Fahrenbruch, A. L.↗
NASA NTRS1974

Thermally-restorable optical degradation and the mechanism of current transport in Cu2S-CdS photovoltaic cells

The photovoltaic properties of single-crystal Cu2S-CdS heterojunctions have been investigated as a function of heat treatment by detailed measurements of the dependence of short-circuit current on photon energy, temperature, and the state of optical degradation or enhancement. A coherent picture is formulated for the relationship between enhancement and optical degradation, and their effect on the transport of short-circuit photoexcited current and dark, forward-bias current in the cell. Optical degradation in the Cu2S-CdS cell is shown to be closely identical to optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal, indicating that the CdS:Cu layer near the junction interface controls carrier transport in the cell. It is proposed that both the photoexcited short-circuit current and the dark, forward-bias current are controlled by a tunneling-recombination process through interface states.

Fahrenbruch, A. L.↗
NASA NTRS1972

Photocapacitance effects at a Cu2S-CdS heterojunction.

The influence of trapped charge on the photovoltaic properties of an efficient Cu2S-CdS single-crystal heterojunction has been studied by a photocapacitance technique. For the nonheat-treated cell, a persistent increment in capacitance as high as 70% of the dark capacitance remained after illumination of the junction by band-gap light at 100 K. The additional capacitance is due to holes trapped in deep levels in the CdS depletion region near the interface. The trapped holes enhanced the 100 K photocurrent spectrum uniformly by a factor of 3 before heat treatment. After a 200 C heat treatment in air, the maximum trapped charge at 100 K enhanced the photocurrent by two orders of magnitude. The results are interpreted in terms of the tunneling through a conduction band spike of electrons photoexcited in the Cu2S.

Lindquist, P. F.↗
NASA NTRS1971

Thermally restorable optical degradation effects in heat-treated Cu2S-CdS crystal heterojunctions.

We have shown that heat treatment alone does not produce appreciable degradation of the short-circuit current in Cu2S-CdS single-crystal photovoltaic heterojunctions. The degradation, which has been commonly observed, is the result of optically induced effects in the heat-treated cell, subsequent to the heat treatment. These optically induced effects can be correlated with photochemical changes induced in single crystals of CdS:Cd:Cu in which the density of Cu acceptors exceeds the density of excess-Cd donors. Major conclusions about the mechanism of the photovoltaic effect and heat-treatment processes can be drawn.

Kanev, S. K.↗