Natural Random Nanotexturing of the Au Interface for Light Backscattering Enhanced Performance in Perovskite Solar Cells

As the efficiency of a solar cell approaches its limits, photonic considerations to further enhance its performance overtake electronic ones. It has been theoretically shown for GaAs solar cells that with the combined effects of a surface random texturing and a perfectly reflecting rear mirror, efficiencies close to the Shockley Queisser limit can be reached, even when the absorber layer is very thin. In here, we demonstrate a method for taking advantage of surface random texturing to enhance the efficiency of planar perovskite solar cells. By naturally transferring the perovskite random nano texturing to the back semiconductor/metal interface, where the contrast in the imaginary part of the refractive index is very large, backscattering reduces light escape from the solar cell structure. This leads to a close to optimal light absorption that allows bringing the cell efficiency from 19.3% to 19.8%. Such a path we opened toward an ergodic behavior for maximum light absorption in perovskite cells may lead to the most efficient perovskite cells ever.