Bulk passivation and suppressing non-radiative recombination loss in a 3D all-inorganic CsPbIBr2 perovskite solar cell via a 2D layered perovskite framework†

Improving perovskite film quality for reducing non-radiative recombination centers is one of the key aspects of designing efficient and stable perovskite solar cells (PSCs). In this work, we fabricated a high-performing and ambient stable CsPbIBr₂-based PSC by incorporating a 2D perovskite framework within a 3D perovskite structure. An optimum amount of 2D doping can anchor the grain boundaries to improve the crystallinity and grain sizes and ultimately suppress non-radiative recombination centers within the perovskite. The solution-processed perovskite film with the structural formula ((PEA)₂PbI₄)_X(CsPbIBr₂)_1−X for X = 0.02 exhibited an improved average grain size of 853.38 ± 0.18 nm in comparison to 350.43 ± 0.09 nm of pristine CsPbIBr₂ thin films. The bulk passivation within the perovskite was supported by the X-ray diffraction, steady-state, and time-resolved photoluminescence results. We fabricated a PSC with the device structure FTO/c-TiO₂/m-TiO₂/(PEA)₂PbI₄)_X(CsPbIBr₂)_1−X/Spiro-OMeTAD/Ag, and achieved a power conversion efficiency (PCE) of 10.13% under ambient conditions with X = 0.02 and only 8.08% PCE for the pristine 3D perovskite (X = 0) device. The devices with 2D incorporation showed excellent ambient stability without any encapsulation and retained 80% of their initial PCE (T₈₀) after 500 hours of ambient storage, whereas the device with pure 3D perovskite retained only 20% of its initial PCE after 400 hours of ambient storage. Simulation results, in combination with the experimental data, show that a reduced density of recombination centers resulted in much improved device performance.