Improving the efficiency of perovskite photovoltaics using a hierarchical 2D/3D/2D structure

Three-dimensional (3D) organometal perovskite solar cells (PSCs) have exhibited remarkable performance. Meanwhile, the crucial hurdle to commercialization is the 3D perovskite's instability. The development of multilayered (2D/3D) junction perovskites as light absorption materials has proven to be one of the most dependable approaches for stabilizing PSCs without compromising their power conversion efficiency (PCE) owing to the passivation capability and hydrophobic nature of the massive organic cations. Herein, hierarchical 2D/3D/2D perovskites with optimized interfaces are developed by using a Dion-Jacobson (2D) phenylethylammonium dimethylammonium lead iodide (PeDAMA₄Pb₅I₁₆) film on the top and a Ruddlesden-Popper (2D) cesium germanium di-iodide dibromide (Cs₂GeI₂Br₂) film at the bottom of a 3D triple-cation Cs_0.07FA_0.85MA_0.08Pb(IBr)₃ perovskite. The initial simulation of the 2D/3D/2D PSC obtained a PCE of 11.75%. Afterward, we systematically optimized the 2D perovskite layer by changing the thickness, bulk defect density, and p-type doping level to attain optimum values. The findings demonstrate that nonradiative recombination in the 2D/3D/2D-structured PSC is substantially suppressed, hence impeding the generation of leakage current. Further optimization of the Cs₂GeI₂Br₂ (2D) perovskite, along with parasitic resistances and temperature, leads to a remarkable enhancement from 18.24% to 27.88%. This process can offer significant insights for the construction of perovskite structures to attain efficient and stable photovoltaic devices.