Tuning the rear side morphology of crystalline silicon solar cells by plasma chemical etching at atmospheric pressure for maximal light trapping effect

Optical properties of textured monocrystalline silicon substrates after single side atmospheric pressure plasma chemical etching (APPCE) were studied in dependence on the treatment conditions in the SF6-O2 gas mixture. This treatment leads to the surface morphology modification, namely to the controlled change of top angles of random pyramids from original 70.5° to resulting 90-150°. Influence of the one side morphology modification of silicon wafers on the resulting optical spectra was calculated by Monte Carlo modeling as well as it was measured by combined T/R characterization. The same modeling approach has been applied to predict the light trapping behavior of solar cell structures with dielectric passivation of the rear side which confirms the increase of the internal reflectivity of c-Si solar cell structure from values of about 65-70% for standard screen-printed Al to well over 90%. Rear side morphology modification (by two various APPCE methods) was applied for the set of c-Si solar cells with Al screen-printed back contact. This process (replacing also the edge isolation step) leads to slight performance increase compared to standard solar cell structure.