Optical Reabsorption Effects in Photoluminescence of Perovskites Conformally Coated on Textured Silicon

Two-terminal fully textured perovskite silicon tandem solar cells have recently advanced significantly and are quickly moving toward scalable production. While µm-sized texturing of the silicon solar cell enables minimizing reflection losses, and tuning of the perovskite layer thickness allows optimizing the photo-generated current distribution between subcells, both approaches introduce challenges at the development stage. One of these challenges is the accurate optoelectronic assessment of perovskite films with photoluminescence (PL) spectroscopy. In this work, we study effects of optical self-absorption on the PL of perovskite films conformally coated on industry-compatible textured silicon with pyramid heights ranging from <1 to >6 µm. Our findings indicate that with increasing pyramid height, the PL peak energy shows a blueshift of 20-30 meV. Similarly, increasing the perovskite thickness on a fixed texture pattern induces a redshift. Three-dimensional confocal laser scanning PL microscopy, combined with statistical ray optical simulations, reveals that photon reabsorption in the perovskite film plays an important role in the texture-dependent and thickness-dependent PL responses. This optical effect, besides previously reported changes in perovskite mechanical properties due to silicon texture, is crucial to consider for accurate assessment of PL, and for efficient optimization of perovskite silicon tandems with advanced optical designs.