01/01/2018
Scheme of micro-concentrator solar cell concept

Scheme of micro-concentrator solar cell concept

Source: BAM, Division Nanomaterial Technologies

In photovoltaics, a rapid progress towards new light-absorbing materials and more sophisticated solar cell designs is being made in pursuing the goals of increasing cell efficiency, reducing production costs and material usage. For this, the micro-concentrator solar cell concept is a promising new approach. The scheme shows a micro-concentrator solar cell arrangement consisting of glass as carrier, a molybdenum layer as electrical back contact, absorber islands in the micrometer range and a front contact. Additionally, the light focusing micro lenses are depicted. This cell concept combines the benefits of material saving and an increase of the solar cell efficiency under concentrated illumination using micro lenses.

Optical micrograph of an array of copper-indium deposits on molybdenum-coated glass. Donor: 20 nm copper, 200 nm indium (left). Single deposit in higher magnification (right).

Optical micrograph of an array of copper-indium deposits on molybdenum-coated glass. Donor: 20 nm copper, 200 nm indium (left). Single deposit in higher magnification (right).

Source: BAM, Division Nanomaterial Technologies

Copper-indium-gallium-diselenide (Cu(In,Ga)Se2, CIGSe) is a direct semiconductor, an excellent solar absorber, and a well-established material in thin film photovoltaic technology with current record cell efficiencies of 22.6 %. The record is held by Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg. Starting from this high level, CIGSe appears very promising for micro-concentrator applications, which especially allow the saving of the rare and costly indium and to further increase the cell efficiency by light concentration.

Together with project partners from the Leibniz Institute for Crystal Growth Berlin (IKZ), the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), and the University of Duisburg-Essen (UDE) different processes for the production of micro absorber islands at defined positions using a femtosecond laser were investigated. It was demonstrated that single-pulse laser-induced-forward-transfer (LIFT) can be used to deposit micron-sized dots of copper and/or indium onto a micro solar cell back-contact (see figures). Such systems can serve as precursors for the bottom-up manufacturing of micro-concentrator solar cells based on copper-indium-gallium-diselenide.

Production of precursors for micro-concentrator solar cells by femtosecond laser-induced forward transfer
Stefan Andree, B. Heidmann, F. Ringleb, K. Eylers, Jörn Bonse, T. Boeck, M. Schmid, Jörg Krüger
Applied Physics A, October 2017, 123:670
BAM Department Materials Protection and Surface Technology, Division Nanomaterial Technologies