Large area colloidal photonic crystals for light trapping in flexible organic photovoltaic modules applied using a roll-to-roll Langmuir-Blodgett method

For the first time, the application of large-area 2D colloidal photonic crystals for light trapping in flexible OPV modules is demonstrated via the study of a broad range of light trapping structures deposited simply and cheaply using our novel roll-to-roll Langmuir-Blodgett technique. Commercially available flexible OPV modules with a size of 10 cm × 14 cm were used. Colloidal silica spheres with diameters ranging from 50 nm to 740 nm were used for the photonic crystal fabrication. The photonic structures made from SiO2 spheres with diameters of 50 nm and 120 nm demonstrate good antireflective properties in the visible and near-infrared spectral range, which have a pronounced positive effect on the photocurrent and the power conversion efficiency in OPV modules at all angles of the light incidence. The 2D photonic crystals made from SiO2 spheres with diameters of 600 nm and 740 nm show strong diffractive scattering of incident light in the forward direction, which results in significant light trapping effects in the OPV modules which again gives rise to an improvement in the cell characteristics. The observed light trapping effects vary only slightly with angle of incidence, suggesting that such photonic crystal layers could be of direct benefit in terms of the response of the OPV modules without the need to track the sun position as it moves across the sky.