Optical loss is one of the main factors that restrict the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Anti-reflective coating and light-trapping structure is one of the effective methods to enhance light capture and thus improve PCE. Through the finite-difference time-domain (FDTD) method, polydimethylsiloxane (PDMS) anti-reflection coatings with different light-trapping structures were introduced in the air–glass interface of planar heterojunction-based PSCs. Calculating the optical absorption, the inverted-pyramid structure had the best anti-reflection performance. On this basis, in order to further improve photon absorption of perovskite layers, an optical coupling structure with double-decker inverted pyramids are designed by inserting an inverted pyramid structure between perovskite layer and TiO2. According to the cross-sectional |E|2 distribution of the EM wave inside the device, three different marshalling patterns of the optical coupling structure are proposed and studied to select the best one for PSCs. This kind of marshalling pattern can highly enhance light harvesting of perovskite solar cells, thus increasing the generation rate of charge carrier in perovskite layers and improving the PCE.