Engineering topics

Murray, Christopher S.

Publications and source records attributed to Murray, Christopher S..

4 records

NASA NTRS2005

n/p/n Tunnel Junction InGaAs Monolithic Interconnected Module (MIM)

The Monolithic Interconnected Module (MIM), originally introduced at the First NREL thermophotovoltaic (TPV) conference, consists of low-bandgap indium gallium arsenide (InGaAs) photovoltaic devices, series interconnected on a common semi-insulating indium phosphide (inP) substrate. An infrared reflector is deposited on the back surface of the substrate to reflect photons, which were not absorbed in the first pass through the structure. The single largest optical loss in the current device occurs int he heavily doped p-type emitter. A new MIM design (pat.pend.) has been developed which flips the polarity of the conventional MIM cell (i.e., n/p rather than p/n), eliminating the need for the high conductivity p-type emitter. The p-type base of the cell is connected to the n-type lateral conduction layer through a thin InGaAs tunnel junction. 0.58 eV and 0.74 eV InGaAs devices have demonstrated reflectances above 90% for wavelengths beyond the bandgap (greater than 95% for unprocessed structures). Electrical measurements indicate minimal voltage drops across the tunnel junction (less than mV/junction under 1200K-blackbody illumnination) and fill factors that are above 70% at current densities (J(sub sc)) above 8 Angstroms per square centimeters for the 0.74eV devices.

Wilt, David M.↗

NASA NTRS2004

InGaAs/InP Monolithic Interconnected Modules (MIM) for Thermophotovoltaic Applications

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between systems efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) devices series -connected on a single semi-insulating indium phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight series interconnected cells. MIM devices, produced from 0,74 eV InGAAs, have demonstrated V(sub infinity) = 3.23 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurement (less than 2 microns) of these devices indicate a reflectivity of less than 82%. MIM devices produced from 0.55 eV InGaAs have also been den=monstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM1) have been demonstrated.

Wilt, David M.↗

NASA NTRS1997

Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

Wilt, David M.↗

NASA NTRS1997

Electrical and Optical Performance Characteristics of p/n InGaAs Monolithic Interconnected Modules

There has been a traditional trade-off in ThermoPhotoVoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A Monolithic Interconnected Module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual Indium Gallium Arsenide (InGaAs) devices series-connected on a single semi-insulating Indium Phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An InfraRed (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74eV InGaAs, have demonstrated V(sub infinity) = 3.2 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. IR reflectance measurements (greater than 2 microns) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55 eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

Wilt, David M.↗