A triple junction, amorphous silicon solar cell under color light bias mounted in the NRL spectral response measurement system
A triple junction, amorphous silicon solar cell under color light bias mounted in the NRL spectral response measurement system

Function
Measures, characterizes, and analyzes photovoltaic materials and devices. The primary focus is the measurement and characterization of solar cell response to exposure to natural and manmade radiation environments. These facilities are used by a range of customers, both commercial and government, for performing experiments ranging from in-depth basic studies of radiation response mechanisms to large-scale product qualification campaigns.

Description
This facility is unique in its combination of measurement, analysis, and modeling capabilities. The laboratory contains the in-house expertise to assess a photovoltaic technology, design and implement the most effective characterization test plan, and analyze the results to produce an in-depth materials characterization and device performance evaluation. Furthermore, using the displacement damage dose analysis technique developed within the laboratory, the experimental results can be rapidly translated into accurate predictions of device performance in essentially any radiation environment, particularly that of Earth orbit.

Measurement Capabilities
The solar cell laboratory boasts a wide array of measurement capabilities. The central feature is a TS Space Systems Triple-zone Close Match Simulator that has three independently controllable light zones—300 to 700 nm, 700 to 1200 nm, and 1200 to 2400 nm—and that produces one-sun, air-mass-zero (AM0) illumination with 2% uniformity over a 28 in2 area with better than 0.5% spectral fidelity from 300 to 2400 nm. In addition, the laboratory contains a Spectrolab X-25 Mark II solar simulator providing one-sun, AM0 illumination with 2% uniformity over a 78 in2 area with 2% spectral fidelity from 300 to 1600 nm. The laboratory also contains a custom-built spectral response system ranging in wavelength from 340 to 2400 nm with specialized light and electrical biasing configuration allowing individual subjunction measurements within multijunction devices to be measured. The laboratory also contains diode dark-current measurement systems, a deep-level transient spectrometer, an electrochemical capacitance-voltage profiler, and a state-of-the-art Hall Effect System.

Radiation Facilities
NRL maintains in-house radiation facilities and has long-standing relationships with facilities at many other government laboratories, providing access to virtually any desired radiation test environment. Focusing on the natural space radiation environment, NRL has established specialized test chambers enabling exposure of multiple large-area solar cells to electron and proton irradiation over a wide range of particle energies and fluxes.