Synthesis of lead-free cesium bismuth iodide perovskite ink for solar cell using flow reactor.

• Synthesized Cs 3 Bi 2 I 9 ink via flow reactor for efficient photovoltaic absorber layers. • Analyzed interfacial defects affecting efficiency, focusing on residence time variations. • Identified optimal performance for Ink 2 at a 60-s residence time. • Enhanced carrier transport and defect tolerance observed in the absorber layer. • Ink 2 achieved Voc = 1.04 V, Jsc = 5.2 × 10−2 mA/cm2, FF = 75.9 %, PCE = 0.6 %. Organometallic halide perovskite materials have gained significance in recent years due to their superior optical characteristics and solution-processability. However, the development of these lead-based compounds is limited by the hazardous heavy-metal element Pb. So, demand for inorganic lead-free perovskite is increasing and Cesium Bismuth Halide can be a potential alternative. The flow reactor method represents a significant advancement in the field of chemical engineering, offering a continuous approach to chemical synthesis and process optimization. In contrast to the traditional batch reactor process, flow reactors facilitate a steady state flow of reactants through the reaction chamber, allowing for superior control over critical reaction parameters such as temperature, pressure, and residence time, enhancing reaction efficiency, higher product yields, and consistent quality. In this study, Cesium Bismuth Iodide (Cs 3 Bi 2 I 9) ink was synthesized utilizing an optimized flow reactor methodology to achieve high-quality perovskite ink suitable for commercial-scale applications. The molar ratio of cesium iodide to bismuth iodide (CsI/BiI 3) was adjusted to 1.5:1, absorption and Tauc plot analyses revealed that the resulting film exhibited a reduced bandgap of 1.95 eV, which is below the expected 2 eV. The mean particle size grows from 153.42 nm to 168.34 nm with residence time. Furthermore, including the reaction's residence time (R T) at 60 s leads to a modest increase in power conversion efficiency (PCE), from 0.4 % to 0.6 %, in the solar cell using conventional TiO 2 and Spiro-OMeTAD as the electron and hole transport material respectively. The results of this research propose that increasing the concentration of precursors could further enhance the performance of lead-free Cs 3 Bi 2 I 9 -based perovskite solar cells. [ABSTRACT FROM AUTHOR]