Large-scale, surfactant-free solution syntheses of Cu(In,Ga)(S,Se) ₂ nanocrystals for thin film solar cells

Large-scale (as much as 200 g in a batch) and surfactant-free syntheses of the CuIn_xGa_1-xSe₂ and the CuIn _xGa_1-xS₂ nanoparticles were investigated by employing a sonochemical process under ambient conditions. This synthetic approach eliminates the need for organic stabilizers, which may act as an insulator in the final device, and reduces the number of reaction steps for synthesis of high-quality CISe nanocrystals. We also demonstrate the solution-based fabrication of the thin film photovoltaic devices with a conversion efficiency of 2.62% by using nanocrystal-based inks. The device was fabricated with 2 μm of a CIGS absorber layer on Mo-coated soda lime glass, 70 nm of a chemical-bath-deposited CdS layer, 100 nm of an intrinsic ZnO layer, followed by 800 nm of a Al-doped ZnO layer. Finally, a patterned Ag (200 nm) grid was deposited on the top of the device. The current results offer a promising alternative for solution-based CIGSe thin film solar cells, with a higher efficiency.