Texturing optimization for bifacial n-PERT: are pyramids and/or black silicon the way to go for thinner devices?

Abstract

Thickness reduction of crystalline silicon (c-Si) solar cell is one of the most efficient ways to reduce the cost of manufacturing process as well as Energy pack-back time (EPBT) and thus ecological footprint. However, thin solar cell goes with a lack of infra-red absorption of the solar spectra. To circumvent this effect, advanced light-trapping schemes involving nanostructured surfaces or black Silicon (b-Si) and/or pyramid textured surfaces are good candidates for light-trapping enhancement in thin bifacial n-PERT solar cell (80-180 µm). In order to identify an optical optimum for thickness reduction, several combinations of different morphologies (Flat, Pyramid, b-Si and Saw damage removal - SDR) were modelled in front and/or rear side. Unfortunately, sizes of nanostructures are in the same range as wavelength of absorbed light, therefore geometrical optics is no more available which makes nanostructure not easy to model with conventional electro-optical simulation software. In this study, we integrate absorptance and reflectance measurements of b-Si into c-Si solar cell modelling process and thus demonstrate a +1%abs efficiency with one side nanotexturing and without antireflection coating layer compared to standard bifacial n-PERT solar cells. Moreover, mixing rear pyramid and front nanotexturing does not enhance significantly Jsc to be considered from a process integration perspective in simulated thickness range (80-180 µm). Nevertheless, such a combination reaches higher light trapping and thus a better resilience to thickness reduction.