Materials efficient deposition and heat management of CuInSe2 micro-concentrator solar cells

- Materials-efficient fabrication method for micro-concentrator solar cells.
- Selective electrodeposited of CuInSe2 into micrometer-sized holes in a SiO2 insulating layer.
- Operational micro solar cell devices with Mo/CuInSe2/CdS/i-ZnO/ZnO structure.
- Beneficial heat management of micro-concentrator solar cells shown by simulations.

Thin-film solar cells based on Cu(In, Ga)Se2 chalcopyrite materials have achieved record power conversion efficiencies (PCE) above 22%, higher than any other thin film technology. Here, a proof-of-principle for Cu(In, Ga)Se2 solar cells with a reduced materials consumption by a factor of ~100 is demonstrated for which simulations indicate an even higher PCE potential. The concept is based on using micrometer-sized solar cells onto which sunlight is concentrated using a lens array. Thereby, all incoming sunlight is absorbed in solar cells that only cover a fraction (on the order of 1/100) of the surface, creating thus significant material savings. A fabrication process based on selective growth of CuInSe2 micro solar cells is presented, using electrodeposition into holes of an insulating SiO2 layer on a Mo back electrical contact. Proof-of-principle micro solar cells using this materials-savings approach are realized and characterized. Additionally, the heat management of micro-concentrator solar cells is studied using finite element simulations. For square micro solar cells up to 100 µm side length the temperature increase due to the concentrated sunlight can be kept below 4 °C above that of a flat panel solar cell. An increase of the PCE by 4.9% is estimated, considering the combined effect of the open circuit voltage increase due to concentrated sunlight, and the PCE decrease due to the temperature increase.

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