Over the past 20 years, SolAero Technologies (now SolAero by Rocket Lab) has been an industry leading supplier of III-V solar cells, solar cell assemblies and solar array panels. Currently, over 1,100 satellites and spacecraft in orbit are powered by our products. These include >100 GEO missions, >900 LEO missions, and 15 lunar and interplanetary missions. State-of-the-art multijunction solar cell technologies and their respective roadmaps will be reviewed, including a comparison of these technologies at end-of-life (EOL) accounting for important differences in on-orbit operating temperatures that are frequently omitted in other analytical comparisons. SolAero's solar array capabilities are discussed, including the design and manufacture of rigid panel substrates and photovoltaic assemblies, as well as SolAero's progress in expanding further into the solar array market by providing fully integrated wing-level solutions for small satellites.

Emcore's latest generation InGaP/InGaAs/Ge ZTJ triple-junction space-grade high-efficiency solar cells have been in volume production since 2009, with over 300,000 flight cells produced to power more than 35 separate satellites. The ZTJ cells, CICs (Coverglass-Interconnected-Cell) and solar panels have also been characterized and qualified to both the AIAA-S-111 and AIAA-S-112 standards. More than 10 life-cycle coupon panels have been thermal cycled to temperature extremes representing varied orbital conditions such as GEO (geosynchronous), LEO (low-earth) and highly elliptical orbits. In its larger 1-cell-per-wafer form factor, the ZTJ solar cell has been used to manufacture solar panels for a dozen NASA and other commercial spacecraft. Currently Emcore Photovoltaics is under contract to NASA's Goddard Space Flight Center (GSFC) to build and deliver the solar panels for the Magnetospheric Multiscale (MMS) Mission and to ATK Space Systems for the Commercial Resupply (CRS) mission to the International Space Station (ISS) and the AMOS-6 commercial telecommunication satellite. In this paper, the results of the qualification, production and testing of the life-cycle coupons and the solar panels for these missions is presented. In addition, the initial on-orbit telemetry performance results of NASA's NuStar (Nuclear Spectroscopic Telescope Array) spacecraft solar array will be presented. The NuStar spacecraft was launched in June of 2012 and built by Orbital Sciences Corporation It is powered by an ATK solar array populated with ZTJ solar cells.

The Emcore One-per-wafer ZTJ solar cell, with a cell area of approximately 60cm(2), is based on the 29.5% efficiency ZTJ triple-junction structure. The performance of this cell has been enhanced via grid design improvements, resulting in a 0.3% absolute efficiency increase. To confirm electrical performance and investigate reliability with respect to the grid metal and form factor changes implemented in the One-per-wafer ZTJ cell, Emcore has performed a series of confidence tests, which the cells successfully passed. Electrical measurements for approximately 14,000 One-per-wafer ZTJ cells manufactured at Emcore show a median AM0 efficiency of 29.3% (1353 W/m(2)).

In collaborations with both Lockheed-Martin (LM) and the Air Force Research Laboratory (AFRL), Emcore has incorporated its cutting-edge IMM cell technologies on MISSE-8 in a variety of cell form factors and two distinct configurations. The first is a double coverglass (DCG) arrangement, where adhesive and coverglass are attached to both the front and backsides of the solar cell, and in the second configuration the IMM cell was mounted to a rigid, lightweight, CTE-matched substrate. Pre-build test coupons were subjected to 1124 thermal cycles from -100 to 100°C, and showed no electrical degradation in six out of seven cells/strings, with the lone degraded cell exhibiting just a 3.5% loss in Jsc and no change in Voc or FF. The average AM0 efficiency (solar constant = 1353 W/m 2 ) of the IMM3J cells flown in this experiment have an average efficiency of 31.3% (omitting an anomalously low-perfoming cell), and the 4cm 2 IMM4J cells 33.1%.

This paper describes an overview of the satellite market trends and the role of high-efficiency multi-junction solar cells in enabling the realization of the high-power spacecrafts for the geosynchronous orbit (GEO), the low-earth orbit (LEO) and interplanetary applications. The global GEO telecom satellite orders in the past few years have seen a relatively stable period since the year 2002 when only 13 satellites were on order worldwide. In the 2003–2007 period, however, 23 to 39 yearly orders were placed, totaling 136 satellite orders in 5 years. New markets such as digital radio and broadband, as well as, emerging markets in regions such as Asia have contributed to this trend. Science & observation and military satellites, typically operating in the LEO and polar orbits, and interplanetary missions to the Moon, Mars, Mercury and the Asteroid Belt have also expanded the smaller size spacecraft orders by government agencies. The gradual replacement of solar arrays powered by silicon cells with arrays powered with much higher efficiency multi-junction cells has significantly augmented the operational capabilities of these satellites. The most recent triple-junction solar cells, for example, exhibit 30% conversion efficiency under air-mass zero (AM0) conditions. These cells produce more than twice the end-of-life (EOL) power than the best space silicon solar cells ever produced. Higher performance (i.e., 33% efficiency) and thinner multi-junction cells, such as the inverted metamorphic (IMM) solar cell technology, presently under development will further enable higher power and lower mass (W/Kg) solar arrays, enabling satellites with greater power and capabilities.

The GaInP2/InGaAs/Ge triple junction device lattice matched to germanium has achieved the highest power conversion efficiency and the most commercial success for space applications [1]. What are the practical performance limits of this technology? In this paper we will describe what we consider to be the practical performance limits of the lattice matched GaInP2/InGaAs/Ge triple junction cell. In addition, we discuss the options for next generation space cell performance.

ATK space systems (ATK) in collaboration with the NASA Glenn Research Center (GRC), the Jet Propulsion Laboratory (JPL), and EMCORE Photovoltaics (EPV), is executing NASA's New Millennium Program (NMP) Space Technology 8 (ST8) Project Formulation Refinement Phase to develop and validate through spaceflight a state-of-the-art solar array system called UltraFlex-175. UltraFlex-175 is a highly evolved and scaled version of the previously flight qualified Mars 01-Lander UltraFlex and employs many advanced technologies. The UltraFlex-175 system promises very high specific power (175 W/g - 220 W/kg BOL), compact stowage volume (>33 kW/m3), high reliability, scalability beyond 7 kW wing sizes, and operational capability for standard, high voltage, multi A.U., and/or high temperature applications. Key technology maturation activities performed (deployment kinematics, deployed dynamics, and power production/survivability) that demonstrate TRL 5-6 achievement will be presented. Subsystem and system level design, development, experimental hardware builds, conducted testing and results, and analytical model correlation activities will be presented. Technology scale-up performance to 7 kW wing sizes and the planned UltraFlex-1 75 flight experiment will also be presented

We present high temperature life testing data on Emcore's GaInP 2 /InGaAs/Ge advanced triple-junction (ATJ) solar cell. One of the most complex materials structures in a solar cell is the metal-semiconductor interconnect interface. Solid-state diffusion of metal into the semiconductor at this interface can lead to shunting and degradation of the solar cell. The rate of diffusion is well known in device physics to be dependent on temperature and the specific metal and semiconductor materials. The purpose of this study was to characterize the survivability and diffusion characteristics of the top metal contacts to the ATJ solar cell. A large number of cells were subjected to accelerated high temperature life tests at 200degC, 220degC, 240degC, and 260degC, for up to 5,000 hours. Bare cells, as well as cells with welded and soldered interconnects were studied. No failures (degradation >2% relative) were observed. Critical conclusions regarding the reliability of the ATJ cell are presented

ABLE Engineering, Inc. (ABLE), in collaboration with the NASA Glenn Research Center (GRC), Jet Propulsion Laboratory (JPL), and EMCORE photovoltaics (EPV), has been selected for the NASA New Millennium Program (NMP) Space Technology 8 (ST8) project to develop and flight validate a state-of-the-art solar array system. The "next generation UltraFlex" (NGU) system is a highly-evolved and large-scaled version of the previously flight qualified Mars 01-Lander UltraFlex and employs many advanced technologies. The NGU system promises very high specific power (175 W/g-220 W/kg BOL), compact stowage volume (>33 kW/m/sup 3/), high reliability, scalability beyond 7 kW wing sizes, and operational capability for standard, high voltage, multi-A.U., and/or high temperature applications. A detailed overview of the ST8 NGU technology in-space validation program is presented. Key technology maturation activities performed (deployment kinematics, deployed dynamics, and power production/survivability) that demonstrate TRL 4+ achievement will be discussed. Completed design, development, analysis, and NGU hardware build (components, subsystems and systems), and test activities are presented. NGU hardware experimental test results will be presented and model correlations will be shown. Continued ST8 NGU technology development plans, maturation approach to increase readiness level (TRL 4+ to TRL 7/8), and planned flight experiment details are also described.

Progress towards achieving a high one-sun air mass 0 (AM0) efficiency in a monolithic dual junction solar cell comprised of a 1.62 eV InGaP top cell and a 1.1 eV InGaAs bottom cell grown on buffered GaAs is reported. The performance of stand-alone 1.62 eV InGaP and 1.1 eV InGaAs cells is compared to that of the dual junction cell. Projected AM0 efficiencies of 15.7% and 16.5% are expected for the 1.62 eV InGaP and 1.1 eV InGaAs cells grown on buffered GaAs. The dual junction cell has a projected one-sun AM0 conversion efficiency of 17%. The projected efficiencies are based upon the application of an optimized anti-reflective coating (ARC) to the as-grown cells. Quantum efficiency (QE) data obtained from the dual junction cell indicate that is is bottom cell current limited with the top cell generating 50% more current than the bottom cell. A comparison of the QE data for the stand-alone 1.1 eV InGaAs cell to that of the 1.1 eV InGaAs bottom cell in the tandem configuration indicates a degradation of the bottom cell conversion efficiency in the tandem configuration. The origin of this performance degradation is at present unknown. If the present limitation can be overcome, then a one-sun AM0 efficiency of 26% is achievable with the 1.62 eV/1.1 eV dual junction cell grown lattice-mismatched to GaAs.

We have achieved a new record efficiency of 17.6%, (AM0) for a p/n InP homo-epitaxy solar cell. In addition, we have eliminated a previously observed photo-degradation of cell performance, which was due to losses in J(sub sc). Cells soaked in AM0 spectrum at one-sun intensity for an hour showed no significant change in cell performance. We have discovered carrier passivation effects when using Zn as the p-type dopant in the OMVPE growth of InP and have found a method to avoid the unexpected effects which result from typical operation of OMVPE cell growth.

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.