Spray Pyrolysis as a Deposition Technique for Morpho Butterfly Inspired Colored Module Glass

The presented work shows the potential of spray pyrolysis for the deposition of optical layers to obtain colored module glass to widen the scope of photovoltaic applications. Based on the Morpho butterfly inspired effect, a multilayer Bragg stack is deposited by alternating aluminum oxide and titanium oxide films. The homogeneity, optical, and structural properties of each material system are first analyzed separately. Ellipsometer thickness mappings showed homogenous layers with a standard deviation in film thickness of +/- 3 nm for 80 nm average thickness. The low average AM1.5g weighted absorptance (AlOx: 0% and TiOX: 2.9% in the wavelength range 300-1200 nm), and difference in refractive indices (AlOX: 1.6 and TiOX: 2.4 at 440 nm) make the layers suitable for constructing Bragg reflectors. The developed layers were then combined into a first simple Bragg reflector (4-layer stack) deposited on silicon and textured glass substrates. Blue, yellow, and red color reflection was demonstrated on silicon substrates. For the deposition on textured glass, optical characterization showed the desired selective reflection within the target wavelength range while remaining transparent and with a low absorptance (average weighted absorptance (wavelength range 300-1200 nm) of 3.7%).