Light scattering by textured transparent electrodes for thin-film silicon solar cells

A model is presented to quantify key surface characteristics and simulate light scattering by textured transparent conducting oxides—an important class of materials for thin-film silicon (Si) solar cells. The characterization routine is solely based on the atomic force microscopy (AFM) height-encoded data and eliminates the need for time-consuming measurements of angle resolved scattering (ARS) and spectrally resolved scattering (SRS) of light. The presented method is intended for fast and precise inline monitoring of textured transparent electrodes for superstrate thin-film single- and tandem-junction Si solar cells in the production environment. Root-mean-square roughness, mean inclination angle and a fit parameter of three-dimensional Fast Fourier Transform (3D FFT) with the information on spatial feature distribution can be routinely measured with a high precision from a single AFM scan and are used to simulate both ARS and SRS dependencies. The model explains the observed difference in peak position and width of the ARS of surfaces with different morphologies. Special focus is on chemically textured aluminum-doped zinc oxide (AZO). Results on traditional monolithic AZO and new multi-layer stack designs are presented. The effect of an ‘insertion’ layer on light scattering properties and 3D FFT ‘fingerprints’ is also discussed.