Improvement of photovoltaic response in perovskite solar cell via all inorganic lead free cubic double La2NiMnO6/Cs3Bi2I9 based graded absorber architecture.

Defect ordered and low dimensional Cs3Bi2I9 planar perovskites have garnered enormous significance in photovoltaic applications due to their remarkable stability against oxygen, heat, and moisture. Despite these advantages, the power conversion efficiencies of Cs3Bi2I9-based planar perovskites remain relatively low. This is primarily attributed to their wide band gap of approximately 2 eV and losses due to interfacial charge recombination. To resolve this issue, this article proposes a novel design of Cs3Bi2I9–La2NiMnO6 based dual absorber composition to form a ITO/ETL/Cs3Bi2I9/La2NiMnO6(LNMO)/HTL multi-heterojunction perovskite solar cell (PSC) architecture. Incorporating La2NiMnO6 oxide material as secondary multifunctional double perovskite absorber layer (DPAL), which possesses a lower band gap of 1.05 eV, as a secondary absorber layer enhances efficient charge separation. This material functions as a hole transport conductor, facilitating the creation of a cascade band-matched hole extraction system with the Cu2ZnSnS4 (CFTS) hole transport material (HTM). Optimized optical response along with precisely aligned energy levels of the proposed Cs3Bi2I9–La2NiMnO6(LNMO) absorber composition greatly attributes in enhanced optical absorption with reduced recombination losses. The critical device parameters of the proposed PSC architecture have been intensively optimized through SCAPS-1D simulator to attain a substantially affordable power conversion efficiency (PCE) of 26.02%%, short circuit current (Jsc) of 42.7 mA/cm2, open circuit voltage (Voc) of 0.863 V, and fill factor (FF) of 75.01% device defect density of 1015 cm−3 under AM 1.5 photo illumination. Notably, the utilization of a dual-absorber structure comprising Cs3Bi2I9 and La2NiMnO6 materials proves to be significantly more efficient in terms of quantum efficiency and wide spectral coverage at optimal values compared to using either material alone as single absorbers. The proposed model achieves a peak efficiency of approximately 90.22% over a spectral range of 300–1200 nm, surpassing the efficiency of 80% attained with a single Cs3Bi2I9 absorber covering a spectral range of 300–980 nm. Additionally, it outperforms the efficiency of 83% achieved by the single La2NiMnO6(LNMO) absorber within the spectral range of 300–1200 nm. [ABSTRACT FROM AUTHOR]