The goal of IEC's research has always been to advance the development
and acceptance of thin-film photovoltaic modules. This research
is often carried out in close collaboration with and in support
of (national) research teams. Our current technical objectives
in each of four thin film solar cell programs are as follows:
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Amorphous Silicon
- Increase the short-circuit currents in the component cells of multijunction devices by reducing optical losses and improving light-trapping.
- Optimize interfaces to improve Voc of component cells in multijunction devices.
- Quantify and reduce the optical and contact losses of multijunction devices as prioritized by the a-Si Research Teams.
Thin poly-Si layers on low cost substrates
Research Facilities and Equipment
The IEC has established the equipment and capabilities required
to conduct leading edge research on thin film photovoltaic materials.
Presently, our ability to deposit a wide range of materials is
made possible with the following equipment:
- a rf plasma CVD reactor for depositing amorphous and microcrystalline
Si layers and solar cells
- a hot wire CVD reactor for depositing polycrystalline Si
- 3 multisource evaporators for depositing CdTe, Cu(In,Ga)Se2 ,
and CdS for polycrystalline thin film solar cells
- chemical bath deposition of CdS
- a selenization reactor for reacting Cu, In, and Ga layers with
Se
- a dc sputtering system for depositing Cu, In, Ga, Mo and Al
- a rf sputtering system for depositing ZnO, ITO, and Mo
- two electron beam evaporators for depositing a wide range of metals
- several ovens and furnaces for annealing and recrystallizing under
various chemical atmospheres
In order to evaluate the wide range of materials deposited in
the above systems, it is necessary to maintain an equally broad
array of equipment for characterization of the materials and the
solar cells. IEC has the following measurement and analysis capabilities:
- scanning electron microscope for structural analysis
- X-ray diffraction for structural and crystallographic analysis
- energy dispersive spectroscopy (or energy dispersive analysis
of X- rays) for compositional analysis
- atomic absorption spectroscopy for chemical analysis
- UV-VIS-IR optical spectrometer for analysis of optical properties
- four-point probe for resistivity measurement
- Hall effect for resistivity and mobility measurement
- temperature controlled current-voltage measurement for conductivity
and solar cell characterization
- laser scanning (or LBIC) for spatial uniformity of photoresponse
- calibrated solar simulator for solar cell performance testing
- spectral response for quantum efficiency measurement
- capacitance for junction characterization
IEC has always made laboratory safety a major concern, and has been a leader among university solar cell research facilities in this regard. We have an extensive interlocked system of hazardous gas detection and containment with back-up power for ventilation.