Optimization of Light Management Layers for Light Harvest of Perovskite Solar Cells

Recently, with rapid development of perovskite solar cells, the record efficiency has exceeded 24.2%. However, the research of efficiency improvement never stops. This work introduces an effective approach to remarkably reduce the device reflection loss by using light management (LM) cover layer. A specific model combined with ray and wave optics was built to numerically optimize the texture of the LM layers for light harvesting in photovoltaics cells and explore the optical principles in the light trapping. The LM layer texture is made of 2D periodic triangle structures. Both symmetric and asymmetric triangle structures were investigated. The results indicate that asymmetric structures possess the close performance compared with symmetric ones, and notably, on contrary to the symmetric structures, the light trapping abilities are much more insensitive to the bottom thicknesses of asymmetric structures. It will benefit the practical fabrication, since the precise bottom thickness control can be avoided. From the optimization results, 3 optimal structures are found. With the optimal LM layers, a thin active layer (165nm) device is able to produce the short circuit current intensities (Jsc) of around 21mA/cm², which is approximately equivalent to the Jsc of a thick active layer (800nm) device without LM layers. Meanwhile, about 23% power conversion efficiency (PCE) enhancement is achieved. On the other hand, active layer thickness also makes influence on the light trapping abilities. As the active layer thickness is increased from 165nm to 800nm, the Jsc only improves by about 2.4mA/cm², while the PCE enhancement is dropped from ~23% to ~11%. In consideration of the compromise between total device energy output and PCE enhancement, as well as material cost reduction, the active layer with around 165nm should be an optimal thickness.