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- Micro-concentrator solar cell (3) (entfernen)
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Indium is a constituent of copper-indium-gallium-diselenide (CIGSe), which is an excellent absorber material for highly-efficient thin film solar cells but a rare element. A micro-concentrator solar cell design can achieve indium saving along with increased solar cell conversion efficiency. In such a solar cell architecture the CIGSe material is arranged in micrometer sized islands in contrast to the deposition of a thin layer used in standard cells.
In this paper, the production of spatially arranged precursor islands consisting mainly of indium using laser-induced forward transfer (LIFT) is presented. The donor is a glass substrate (150 µm thick) coated with layers of copper (20-150 nm) and indium (200-1000 nm). The receiver is an 800 nm thick molybdenum film on glass intended as back contact for CIGSe solar cells. Islands of the donor material are successfully transferred via LIFT by employing 30-fs laser pulses with 800 nm wavelength and 60 µm focal spot diameter. The spacing between donor and receiver is fixed at 150 µm and the material transfer is performed by a single pulse for each precursor island. The transferred material is characterized by scanning electron and optical microscopy, profilometry and energy dispersive X-ray analyses. Matrices of copper-indium precursors can be transferred in a spatial arrangement adapted to the geometry of micro lens arrays needed for micro-concentrator solar cells.
Micro-concentrator solar cells offer an attractive way to further enhance the efficiency of planar-cell technologies while saving absorber material. Here, two laser-based bottom-up processes for the fabrication of regular arrays of CuInSe2 and Cu(In,Ga)Se2 microabsorber islands are presented, namely one approach based on nucleation and one based on laser-induced forward transfer.
Additionally, a procedure for processing these microabsorbers to functioning micro solar cells connected in parallel is demonstrated. The resulting cells show up to 2.9% efficiency and a significant efficiency enhancement under concentrated Illumination.
Single-pulse femtosecond laser-induced forward transfer (LIFT, 30 fs, 790 nm) is used to deposit micron-sized dots of copper and/or indium onto a molybdenum layer on glass. Such systems can serve as precursors for the bottom-up manufacturing of micro-concentrator solar cells based on copper-indium-gallium-diselenide. The influence of the thickness of the copper, indium and combined copper-indium donor layers on the quality of the transferred dots was qualified by scanning electron microscopy, energy-dispersive X-ray analysis, and optical microscopy. The potential for manufacturing of a spatial arrangement adapted to the geometry of micro-lens arrays needed for micro-concentrator solar cells is demonstrated.