Engineering topics

Lowe, Roland

Publications and source records attributed to Lowe, Roland.

3 records

NASA NTRS1994

InGaAs PV Device Development for TPV Power Systems

lndium Gallium Arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 eV on Indium Phosphide (InP) substrates. Reported efficiencies have been as high as 11.2% (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8% efficiency under a 1500 K blackbody with a projected efficiency of 29.3%. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8% and 6% respectively under similar conditions. Low long wavelength response and high dark currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

Wilt, David M.↗

NASA NTRS1994

Pulsed Laser Illumination of Photovoltaic Cells

In future space missions, free electron lasers (FEL) may be used to illuminate photovoltaic array receivers to provide remote power. The induction FEL and the radio-frequency (RF) FEL both produce pulsed rather than continuous output. In this work, we investigate cell response to pulsed laser light which simulates the RF FEL format, producing 50 ps pulses at a frequency of 78 MHz. A variety of Si, GaAs, CaSb and CdInSe2 (CIS) solar cells are tested at average incident powers between 4 mW/sq cm and 425 mW/sq cm. The results indicate that if the pulse repetition is high, cell efficiencies are only slightly reduced by using a pulsed laser source compared to constant illumination at the same wavelength. Because the pulse separation is less than or approximately equal to the minority carrier lifetime, the illumination conditions are effectively those of a continuous wave laser. The time dependence of the voltage and current response of the cells are also measured using a sampling oscilloscope equipped with a high frequency voltage probe and current transformer. The frequency response of the cells is weak, with both voltage and current outputs essentially dc in nature. Comparison with previous experiments shows that the RF FEL pulse format yields much more efficient photovoltaic conversion of light than does an induction FEL pulse format.

Yater, Jane A.↗

NASA NTRS1994

InGaAs PV Device Development for TPV Power Systems

Indium gallium arsenide (InGaAs) photovoltaic devices have been fabricated with bandgaps ranging from 0.75 eV to 0.60 eV on Indium Phosphide (InP) substrates. Reported efficiencies have been as high as 11.2 percent (AMO) for the lattice matched 0.75 eV devices. The 0.75 eV cell demonstrated 14.8 percent efficiency under a 1500 K blackbody with a projected efficiency of 29.3 percent. The lattice mismatched devices (0.66 and 0.60 eV) demonstrated measured efficiencies of 8 percent and 6 percent respectively under similar conditions. Low long wavelength response and high dark currents are responsible for the poor performance of the mismatched devices. Temperature coefficients have been measured and are presented for all of the bandgaps tested.

Wilt, David M.↗